A survey and experiments exploring light transmitting concrete

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TRANSLUCENT CONCRETE
A Survey and Experiments Exploring Light Transmitting Concrete
by
Chinmai Shrikant Shimpi

A Thesis Presented to the
FACULTY OF THE USC SCHOOL OF ARCHITECTURE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF BUILDING SCIENCE

August 2022

Copyright 2022 Chinmai Shrikant Shimpi
ii

Acknowledgements

I would like to express my profound gratitude to my parents for supporting my two-year study at the
School of Architecture at USC. I really appreciate my thesis chair Professor Douglas Noble for continued
support, guidance, and encouragement throughout the research.
I would also like to express my appreciation to my thesis members Professor Robert Ley, and Professor
Marc Schiler. I also want to specially thank Robert Ley for sharing his knowledge and expertise on materials
and material processes.
I would also like to express my appreciation for the people at the Laser cutting and the Wood Shop for
their support.
Lastly, I want to thank you to all my fellow students and faculty in our MBS family for supporting and
helping me in these two years and throughout the research and development of this thesis.
Thesis Committee
Chair:
Douglas Noble, FAIA
Associate Dean for Academic Affairs
Associate Professor
USC School of Architecture
dnoble@usc.edu

Thesis Committee Member 2:
Rob Ley
Adjunct Professor
Professor of Practice in Architecture
USC School of Architecture
rley@usc.edu

Thesis Committee Member 3:
Marc Schiler
Professor
USC School of Architecture
marcs@usc.edu

iii

Table of Contents

Acknowledgements ....................................................................................................................................... ii
List of Tables ................................................................................................................................................ vi
List of Figures ............................................................................................................................................... vi
Abstract ........................................................................................................................................................ xi
Chapter 1 ....................................................................................................................................................... 1
1. Introduction .............................................................................................................................................. 1
1.1 Typical Materials ................................................................................................................................. 2
1.1.1 Optical fibers ................................................................................................................................ 2
1.1.2 Cement ......................................................................................................................................... 4
1.2 History of Light transmitting concrete ................................................................................................ 5
1.3 Manufacture of Translucent concrete ................................................................................................ 5
1.4 Properties of Light Transmitting or Translucent Concrete ................................................................. 7
1.4.1 Light Transmission ....................................................................................................................... 7
1.4.2 Durability ...................................................................................................................................... 8
1.4.3 Mechanical and physical properties ............................................................................................ 8
1.4.4 Energy savings .............................................................................................................................. 8
1.4.5 Advantage and disadvantages of Translucent concrete .............................................................. 9
1.5 Defining Translucent Concrete for this research .............................................................................. 10
1.5.1 Light Transmitting Elements ...................................................................................................... 10
1.5.2 Openings .................................................................................................................................... 11
Chapter 2 ..................................................................................................................................................... 12
2. Literature Review .................................................................................................................................... 12
2.1 “Research and development of plastic optical fiber based smart transparent concrete” - Zhi Zhou
Et al. ........................................................................................................................................................ 12
2.2 “Preparation and study of resin translucent concrete products” - Juan, Shen, and Zhou Zhi (2019)
................................................................................................................................................................ 15
2.3 “Light Transmitting Lightweight Concrete with Transparent Plastic Bar” - Byoungil Kim ................ 18
2.4 Manufacturers of Translucent Concrete ........................................................................................... 21
2.4.1 LiTraCon LTD .............................................................................................................................. 21
2.4.2 LUCEM GMBH ............................................................................................................................ 24
2.4.3 Dupont Lightstone ..................................................................................................................... 27
2.4.4 Luccon ........................................................................................................................................ 28
iv

2.4.5 Fapinex ....................................................................................................................................... 30
2.5 Morphology Study: ........................................................................................................................... 31
2.5.2 Stuttgart City Library in Germany .............................................................................................. 32
2.5.3 Cella Septichora/Pecs, Hungary ................................................................................................. 33
2.5.4 Mont Blanc, Tokyo ..................................................................................................................... 33
2.5.5 Italian Pavilion at the Shanghai Expo in 2010 ............................................................................ 34
2.5.6 Bathing Hall at Obermain Therme in Bad Staffelstein, Germany .............................................. 35
2.5.7 Iberville Veterans Memorial ...................................................................................................... 35
2.5.8 New Headquarters of Bank of Georgia ...................................................................................... 36
2.5.9 RWTH Aachen University ........................................................................................................... 36
2.5.10 Wahat Al Karama ..................................................................................................................... 37
2.5.11 Martyr’s Memorial & Museum ................................................................................................ 38
2.5.12 Nino Arabella ........................................................................................................................... 39
2.5.12 Capital Bank branch, Amman ................................................................................................... 39
2.5.13 NEO - Concrete Bubbles, 2018 ................................................................................................. 40
2.5.14 Breezeblock House ................................................................................................................... 41
2.5.15 Dutch Design Week in Eindhoven ............................................................................................ 42
2.5.16 Plastic bottle School in Philippines .......................................................................................... 43
2.5.17 Signal Iduna, Dortmund ........................................................................................................... 43
2.5.18 Earthships, Taos County ........................................................................................................... 44
2.6 Conclusion ......................................................................................................................................... 45
Chapter 3 ..................................................................................................................................................... 48
3. Methodology ........................................................................................................................................... 48
3.1 Experimenting with concrete flowability .......................................................................................... 49
3.1.2 Exploring with 3D Geometries ................................................................................................... 51
3.2 Fiberglass used in GFRC panels ......................................................................................................... 51
3.3 Acrylic Fibers ..................................................................................................................................... 53
3.4 Plastruct rods .................................................................................................................................... 55
3.5 Glass Capillary Tubes ......................................................................................................................... 56
3.6 Light transmitting formwork ............................................................................................................. 57
3.6.1 3D printed formwork - 1 ............................................................................................................ 57
3.6.2 3D printed formwork - 2 ............................................................................................................ 61
3.7 Epoxy resin light transmitting form .................................................................................................. 64
v

3.8 Conclusion ......................................................................................................................................... 67
Chapter 4 ..................................................................................................................................................... 68
4. Fabrication of prototypes ....................................................................................................................... 68
4.1 Testing Quikrete concrete mix and formability of concrete using a polygonal mold or formwork . 69
4.2 Prototype 1 – Using fiberglass used in GFRC Panels ......................................................................... 71
4.3 Prototype 2 – Using Acrylic Fibers .................................................................................................... 77
4.4 Prototype 3 – Using Plastruct rods ................................................................................................... 82
4.5 Prototype 4 – Using Glass Capillary Tubes ........................................................................................ 85
4.6 Prototype 5 - 3D printed Light Transmitting network ...................................................................... 87
4.6.1 Prototype 5A Production ........................................................................................................... 88
4.6.2 Prototype 5B Production ........................................................................................................... 89
4.6.2 Prototype 5C Production ........................................................................................................... 91
4.7 Prototype 6 - Epoxy Resin light transmitting network ...................................................................... 93
Chapter 5 ................................................................................................................................................... 102
5. Results ................................................................................................................................................... 102
5.1 Testing Quikrete concrete mix and formability of Concrete using a polygonal mold or formwork
.............................................................................................................................................................. 102
5.2 Prototype 1 – Using glass fibers used in GFRC Panels .................................................................... 102
5.3 Prototype 2 – Using Acrylic Fibers .................................................................................................. 106
5.4 Prototype 3 – Using Plastruct rods ................................................................................................. 107
5.5 Prototype 4 – Using Glass Capillary Tubes ...................................................................................... 108
5.6 Prototype 5 - 3D printed Light Transmitting network .................................................................... 109
5.7 Prototype 6 - Epoxy Resin light transmitting network .................................................................... 112
Chapter 6 ................................................................................................................................................... 114
6. Discussion and Conclusion .................................................................................................................... 114
Chapter 6.1 Discussion .......................................................................................................................... 114
Chapter 6.2 Future work ....................................................................................................................... 116
Chapter 6.2.1 Short term .................................................................................................................. 116
Chapter 6.2.2 Long term ................................................................................................................... 118
References ................................................................................................................................................ 120

vi

List of Tables
Table 1 Cement Mix Proportions in kg/m3 (Kim, B. 2017) ......................................................................... 19
Table 2 LiTraCon product specification ....................................................................................................... 24
Table 3 Technical specifications of the different panel types .................................................................... 27
Table 4 Translucent Concrete Morphology ................................................................................................ 45
Table 5 Materials experimented ................................................................................................................. 48
Table 6 Diagonal looping configuration ...................................................................................................... 54
Table 7 Diagonal looping configuration ...................................................................................................... 80
Table 8 Results .......................................................................................................................................... 115
List of Figures
Figure 1 Light Transmitting Concrete Wall (https://www.designbuild-network.com/projects/litracon/) .. 1
Figure 2 Types of fiber optics (https://www.cables-solutions.com/three-common-types-of-fiber-optic-
cables.html) ................................................................................................................................................... 4
Figure 3 Light Transmitting Concrete Wall (https://trends.archiexpo.com/litracon/project-150341-
214131.html) ................................................................................................................................................. 5
Figure 4 Machine that produces the fabric (left) and material structure (right) (Halbiniak, J., et al.) ......... 6
Figure 5 Fig. Transparent fabric made by pultrusion (Halbiniak, J., et al.) ................................................... 6
Figure 6 Optical fiber arrangement (Luhar, et al., 2021) .............................................................................. 7
Figure 7 Fibers in the epoxy resin block mold (Zhou, Z., et al., 2009) (Left) ............................................... 13
Figure 8 POF based epoxy resin block (Zhou, Z., et al., 2009) (Right) ......................................................... 13
Figure 9 Mold for Smart Concrete block (Zhou, Z., et al., 2009) (Left) ....................................................... 13
Figure 10 POF based Concrete block (Zhou, Z., et al., 2009) (Right) .......................................................... 14
Figure 11 Mix ratio of mortar used ............................................................................................................. 15
Figure 12 Cube Prototype (Juan et al. 2019) .............................................................................................. 16
Figure 13 Devices for the silicone mold (Juan et al. 2019) ......................................................................... 16
Figure 14 Fabrication of the silicone mold (Juan et al. 2019) ..................................................................... 16
Figure 15 Resin Light Guide Body (Juan et al. 2019) ................................................................................... 17
Figure 16 Fabrication of RTMC block (Juan et al. 2019) ............................................................................. 17
Figure 17 Resin translucent concrete block (Juan et al. 2019) ................................................................... 18
Figure 18 Transparent acrylic rods and pipes (Kim, B. 2017) ..................................................................... 19
Figure 19 Different molds (Kim, B. 2017) .................................................................................................... 19
Figure 20 Production process (Kim, B. 2017) .............................................................................................. 20
Figure 21 Finished product with different light sources (Kim, B. 2017) ..................................................... 20
Figure 22 Visual object effect before and after surface treatment (Kim, B. 2017) .................................... 21
Figure 23 The Garden Pavilion (http://litracon.hu/en/references/20) ...................................................... 22
Figure 24 The Garden Pavilion (http://litracon.hu/en/references/20) ...................................................... 22
Figure 25 LiTraCon Classic (http://www.litracon.hu/en/products/litracon-blokk) .................................... 22
Figure 26 LiTraCon pXL (http://www.litracon.ca/en/references/21) ......................................................... 23
Figure 27 LiTraCon pXL (http://www.litracon.hu/en/products/litracube-lampa) ..................................... 23
Figure 28 Lucem Lichtbeton Panels (https://www.bft-
international.com/en/artikel/bft_Smooth_translucent_concrete_presented_for_the_first_time_3420
419.html) ..................................................................................................................................................... 25
vii

Figure 29 Ulmer White; Grey Calcilith, and Anthracite Calcilith (From left to right) .................................. 25
Figure 30 LUCEM Starlight (https://www.stylepark.com/en/lucem/lucem-starlight) ............................... 26
Figure 31 LUCEM Line (https://www.stylepark.com/en/lucem/lucem-starlight) ...................................... 26
Figure 32 LUCEM Label (https://www.stylepark.com/en/lucem/lucem-label) .......................................... 26
Figure 33 Dupont Lightstone LED screens (http://dupontlightstone.com/om.html) ................................. 28
Figure 34 Cross-section of Dupont LED panels (Dupont Catalog) ............................................................... 28
Figure 35 LUCCON Translucent concrete panels (https://design-milk.com/luccon-transparent-
concrete/) ................................................................................................................................................... 29
Figure 36 Steps made using LUCCON translucent concrete (https://design-milk.com/luccon-
transparent-concrete/) ............................................................................................................................... 29
Figure 37 Optical fiber composition used by LUCCON (http://www.luccon.com/en/product/) ................ 30
Figure 38 Translucent concrete panels (https://www.fapinex.com/products_details/light-
transmitting-concrete) ................................................................................................................................ 30
Figure 39 Translucent concrete with optical fibers (https://www.fapinex.com/products_details/light-
transmitting-concrete) ................................................................................................................................ 31
Figure 40 Al Aziz Mosque (https://inhabitat.com/unique-light-transmitting-concrete-makes-abu-
dhabis-gorgeous-al-aziz-mosque-glow/) .................................................................................................... 32
Figure 41 Stuttgart City Library Façade ....................................................................................................... 32
Figure 42 Cella Septichora .......................................................................................................................... 33
Figure 43 Mont Blanc Façade panels (https://slidetodoc.com/ron-losonczi-npp-annual-conference-
reykjavk-11-th/) .......................................................................................................................................... 33
Figure 44 Italian Pavilion facades (https://www.heidelbergcement.com/en/italian-pavilion-shanghai) .. 34
Figure 45 Bathing Hall structure (https://www.world-architects.com/en/architecture-news/products/
a-salt-crystal-made-with-lucem-translucent-concrete) .............................................................................. 35
Figure 46 Iberville Veterans panels (http://www.litracon.hu/hu/referenciak/30) .................................... 36
Figure 47 Interior Panels (https://www.archdaily.com/228934/new-headquarters-of-bank-of-georgia
-illuminated-translucent-concrete-for-interior-design-architectural-group-partners) .............................. 36
Figure 48 LED façade panels at RWTH Aachen https://www.architectureanddesign.com.au/news/
world-s-first-light-transmitting-concrete-facade# ...................................................................................... 37
Figure 49 Light transmitting elements on floor (https://lucem.com/works/memorial-abu-dhabi-uae/) .. 38
Figure 50 Light element in translucent (https://lucem.com/translucent-concrete/lucem-label/) ............ 38
Figure 51 Translucent panels (https://lucem.com/works/nino-arabella/) ................................................. 39
Figure 52 Light transmitting panels on the staircase (https://www.archdaily.com/902421/capital-
bank-of-jordan-paradigm-dh) ..................................................................................................................... 40
Figure 53 Interior Panels https://www.designboom.com/architecture/translucent-concrete-bubbles-
tengbom-butong-sweden-10-28-2018/ ...................................................................................................... 40
Figure 54 Construction process (left) and Detail (right) ............................................................................. 41
Figure 55 Breezeblock screen (https://www.archdaily.com/951058/breeze-blocks-house-tamara-
wibowo-architects) ..................................................................................................................................... 41
Figure 56 Zospeum Installation (https://archello.com/product/zospeum) .............................................. 42
Figure 57 Production method at Zospeum (https://metropolismag.com/products/clear-breakthrough
-zospeum-takes-translucent-concrete-next-level/) .................................................................................... 42
Figure 58 School interiors (left) and Production method (Right) (https://insteading.com/blog/plastic-
bottle-schools/) ........................................................................................................................................... 43
viii

Figure 59 Plastic bottles from inside during construction method (https://insteading.com/blog/plastic
-bottle-schools/) ......................................................................................................................................... 43
Figure 60 Fig. Elevator panels – LUCEM Line (https://lucem.com/works/signal-iduna-dortmund-
germany/) ................................................................................................................................................... 43
Figure 61 Inside of Mike Reynold’s Earthship
(https://www.santafenewmexican.com/pasatiempo/columns/art_of_space/gimme-sustainable-
shelter-the-earthships-of-taos-county/article_1beac6f9-0a4a-5cac-a109-7dff1aea97a3.html) ............... 44
Figure 62 Quikrete “Concrete Patching Compound” .................................................................................. 49
Figure 63 Mold geometry ........................................................................................................................... 51
Figure 64 Prototypes of 3D Geometry alternatives .................................................................................... 51
Figure 65 Formwork dimensions in plan (left) and section (right) ............................................................. 52
Figure 66 Formwork dimensions in plan (left) and section (right) ............................................................. 54
Figure 67 PETG 3D printer filament (https://www.amazon.com/Gizmo-Dorks-Filament-Printers-
Transparent/) .............................................................................................................................................. 58
Figure 68 Step 1: 3D print translucent PETG as the light transmitting element......................................... 58
Figure 69 Step 2: Translucent element inserted in wooden form .............................................................. 59
Figure 70 Step 3: Concrete poured in wooden form .................................................................................. 59
Figure 71 Step 4: Set component removed from form ............................................................................... 60
Figure 72 Step 5: 3D printed form extruding out is cut .............................................................................. 60
Figure 73 Step 6: Form flipped over ........................................................................................................... 60
Figure 74 Step 7: PETG 3d printed bed sanded off to reveal the elements running across the thickness
of the panel ................................................................................................................................................. 61
Figure 75 Step 1: 3D printed translucent PETG as the light transmitting element layer by layer .............. 61
Figure 76 Step 2: Attaching the layers ........................................................................................................ 62
Figure 77 Step 3: Placing the translucent form in the formwork ............................................................... 62
Figure 78 Step 4: Pouring concrete in the formwork.................................................................................. 63
Figure 79 Step 5: Placing the translucent form in the formwork ............................................................... 63
Figure 80 Step 6: Grinding concrete till reveal the elements running across the thickness of the panel .. 63
Figure 81 Translucent element to be 3D printed ........................................................................................ 64
Figure 82 Silicone used for the creation of the mold ................................................................................. 65
Figure 83 Epoxy used for the creation of the light transmitting element .................................................. 66
Figure 84 Acrylic Formwork Production ..................................................................................................... 70
Figure 85 Pouring Concrete ........................................................................................................................ 70
Figure 86 Continuous Glass Fibers .............................................................................................................. 71
Figure 87 Formwork Materials .................................................................................................................... 72
Figure 88 Formwork .................................................................................................................................... 73
Figure 89 Winding method ......................................................................................................................... 74
Figure 90 Looping configuration ................................................................................................................. 74
Figure 91 Concrete mix poured into formwork .......................................................................................... 75
Figure 92 Formwork partially removed ...................................................................................................... 76
Figure 93 Concrete block with fibers removed from the formwork ........................................................... 76
Figure 94 Finished block.............................................................................................................................. 77
Figure 95 Finished block close-up ............................................................................................................... 77
Figure 96 Plastic optic fibers (from Amazon; Company Azimom) .............................................................. 78
ix

Figure 97 Wooden Formwork with nails on either side ............................................................................. 79
Figure 98 Looping configurations ............................................................................................................... 80
Figure 99 Optical fiber looping configuration ............................................................................................. 80
Figure 100 Pouring of cement mixture ....................................................................................................... 81
Figure 101 Prototype with cement mixture................................................................................................ 81
Figure 102 Finished prototype .................................................................................................................... 82
Figure 103 Plastruct rods ............................................................................................................................ 82
Figure 104 Material in formwork ................................................................................................................ 83
Figure 105 Concrete poured in the form work ........................................................................................... 84
Figure 106 Finished prototype .................................................................................................................... 85
Figure 107 Capillary Tubes .......................................................................................................................... 85
Figure 108 Weaving of capillary tubes through formwork ......................................................................... 86
Figure 109 Finished prototype .................................................................................................................... 87
Figure 110 Geometry of prototype 5A ........................................................................................................ 88
Figure 111 3D printed light transmitting formwork ................................................................................... 89
Figure 112 Close up of 3D printed light transmitting formwork ................................................................ 89
Figure 113 Geometry of prototype 5B ........................................................................................................ 90
Figure 114 3D printed light transmitting formwork ................................................................................... 91
Figure 115 Geometry of prototype 5C ........................................................................................................ 92
Figure 116 3D printed light transmitting formwork ................................................................................... 92
Figure 117 3D printed light transmitting formwork ................................................................................... 93
Figure 118 3D printed light transmitting formwork ................................................................................... 93
Figure 119 3D printed network ................................................................................................................... 94
Figure 120 Wooden Form ........................................................................................................................... 95
Figure 121 Edge protection ......................................................................................................................... 95
Figure 122 Placing the 3D printed network in the wooden form ............................................................... 96
Figure 123 Placement of 3D printed geometry .......................................................................................... 96
Figure 124 Applying a light coat of oil ......................................................................................................... 97
Figure 125 Silicone mold mixture ............................................................................................................... 97
Figure 126 Pouring the silicone mixture in the mold .................................................................................. 98
Figure 127 Silicone mold with the 3D printed formwork ........................................................................... 98
Figure 128 End conditions of silicone mold ................................................................................................ 99
Figure 129 Epoxy Resin mixture .................................................................................................................. 99
Figure 130 Pouring the epoxy resin into silicone mold ............................................................................. 100
Figure 131 Epoxy Resin curing the silicone mold ...................................................................................... 100
Figure 132 Epoxy Resin formwork ............................................................................................................ 100
Figure 133 Epoxy Resin formwork ............................................................................................................ 101
Figure 134 Epoxy Resin formwork ............................................................................................................ 101
Figure 135 Pouring Concrete .................................................................................................................... 102
Figure 136 Light Transmission through 10 loop configuration ................................................................. 103
Figure 137 Sanded down fibers in 10 loops .............................................................................................. 104
Figure 138 Light Transmission through 30 loop configurations ............................................................... 104
Figure 139 Sanded down fibers in 30 loops .............................................................................................. 104
Figure 140 Light Transmission through 50 loop configuration ................................................................. 105
x

Figure 141 Sanded down fibers in 50 loops .............................................................................................. 105
Figure 142 Light transmission through the block ..................................................................................... 106
Figure 143 Looping of fibers evident when seen closely .......................................................................... 106
Figure 144 Light transmission through the block ..................................................................................... 107
Figure 145 Light transmission through the block after sanding the rods ................................................. 108
Figure 146 Light transmission through the block ..................................................................................... 108
Figure 147 Differential light transmission due to capillary breaking ........................................................ 109
Figure 148 Light transmission through the block ..................................................................................... 109
Figure 149 3D printed light transmitting formwork – Prototype 5A ........................................................ 110
Figure 150 3D printed light transmitting formwork – Prototype 5B ........................................................ 111
Figure 151 3D printed light transmitting formwork ................................................................................. 111
Figure 152 Epoxy resin network ............................................................................................................... 113
Figure 153 Epoxy resin network edges ..................................................................................................... 113

xi

Abstract
Light-transmitting concrete or translucent/transparent concrete has gained traction in the last couple of
decades using certain specific materials such as optical fibers as the translucent aggregates. These are
typically either glass or plastic fibers that are very delicate owing to their small diameters, making the
process of production of the translucent concrete blocks extremely tedious requiring highly skilled labor.
These limitations in the existing processes of production also makes the material very expensive to be
used extensively throughout the world. However, its large-scale use might contribute to significant energy
savings worldwide. Thus, efficient methods of production and materials need to be explored and
experimented. The findings show that there are better methods and materials such as glass reinforced
concrete fibers, 3D printed translucent materials, and epoxy resin framework created by epoxy resin liquid
that is poured in molds and allowed to solidify and act as the medium of light transmittance through the
panel that can be placed in the concrete. These methods are easier to produce and do not require skilled
labor. After performing a light transmission test on the prototypes, the results showed that the light
transmittance is high. Thus, translucent concrete as a material, through the new methods of production
that have been explored, proves to be improve sustainability by allowing light penetration and reducing
the use of energy.
Hypothesis Statement:
Large-scale production of translucent concrete panels is currently limited to the use of fiber optics as the
material that allows the transmission of light through. However, owing to the minute nature of optical
fibers the production method is tedious and expensive. Alternative and methods of production using
alternative translucent aggregates than optical fibers need to be explored and documented that will be
more efficient than the existing process.

xii

Research objectives:
• To create a directory of existing translucent concrete projects in the world and classifying them
depending on characteristics.
• To identify new translucent materials that can be used as the aggregate allows light to pass through
the panels and recognize the feasibility of the material.
• Using the information from the production process, create a manual that lists the steps in the
production of light transmitting panel
1

Chapter 1
1. Introduction
Concrete has been widely used in construction of buildings as a structural material. Recently, researchers
and innovators have been working towards finding novel ways of using concrete to the benefit of its
applications. (Zielińska, M., & Ciesielski, A., 2017) Translucent concrete is one such novel way that has
seen development in the last few decades. (See figure 1)

Figure 1 Light Transmitting Concrete Wall (https://www.designbuild-network.com/projects/litracon/)
Translucent concrete is made of a combination of concrete and a light transmitting element, which is most
commonly optical fibers. (Zielińska, M., & Ciesielski, A., 2017) These optical fibers must pass through the
full thickness of the panel to transmit light from one end to the other. (Zielińska, M., & Ciesielski, A., 2017)
The material properties of light transmission coupled with increased structural strength make the material
very interesting. The material also has sustainable capabilities since it allows daylight to enter the space
thus reducing energy usage for lighting purposes in the building. This, in turn, reduces energy costs that
the building owners (and the planet) have to bear.
The examined concept of light transmitting concrete is based on ‘Nano Optics’, which means the passing
of light through materials that can be measured on a nanometric scale. (Concrete, S., 2020) Translucent
concrete is gaining popularity due to its translucent character that allows light into the space and high
2

strength. (Zielińska, M., & Ciesielski, A., 2017) The matrix formed by the optical fibers running between
the interior and exterior faces of the panels tranmsit the light. (Valambhiya, H. B., Tuvar, T. J., & Rayjada,
P. V. 2017). This matrix creates an internal structure and gets well integrated with the concrete mixture
to act as a structural reinforcement in the panel. (Concrete, S., 2020)
There are various applications of translucent concrete. Some of these include load bearing walls, interior
partitions, exterior facade panels, and floor panels, as well as lamps. Illumination can be added to the
back of these panels to create special light effects to create interesting designs. (Valambhiya, H. B., Tuvar,
T. J., & Rayjada, P. V. 2017). A sky-like appearance can also be created using optical fibers of varying
diameters. Logos can also be made by setting the light transmitting elements in the pattern of the writing
or symbols.
1.1 Typical Materials
1.1.1 Optical fibers
The idea of using light to send messages was developed in the eighth century by the Greeks to send signals.
(Sawant, et al., 2014) In the mid-1900s the great transmission power of optical fibers was discovered and
sparked a revolution in its varied use. Today, optical fibers are typically made of glass and plastic since
these materials make it possible for the fibers to be thin and long.
The optical fiber consists of 3 main parts: the core, cladding and buffer coating. The core transfers the
information from the transmitter to the receiver, or in this case, transfers light from one end to another.
(Zielińska, M. et al. 2017) It is made of a dielectric material which means that it does not pass electricity
and this material is usually glass. (TKM Institute of Technology, 2015) The diameter of the core ranges
from 5 microns to 100 microns and has great transmitting abilities without the significant reduction of
intensity of light that is passing through. (TKM Institute of Technology, 2015)
3

The cladding is the outer material which helps keep the light rays inside the core. (TKM Institute of
Technology, 2015) The loss of light from the core to the outside is reduced by reducing the scattering of
light rays. (TKM Institute of Technology, 2015) The cladding also performs the functions of protecting the
fiber from absorbing surface contaminants and adds strength to the filigree core. (TKM Institute of
Technology, 2015)
These optical fibers transmit light due to the principle of total internal refraction and reflection. The
refractive index of the core is high whereas the refractive index of the cladding is lower. The light waves
passing through the core strike the cladding and are refracted as well as reflected back towards the inside
and the process continues until the light ray reaches the other end. (Sawant, et al., 2014)
The buffer coating is a protective coating made of silicon rubber and acts as an extra coating to protect
the fibers from physical damage. It prevents abrasion of the fibers and intercepts scattering losses caused
by micro bends. (TKM Institute of Technology, 2015) Optical fibers can be classified into 3 on the basis of
their refractive index profiles: multimode step index, multimode step-index, single mode. (See figure 2)
(Luhar, et al., 2021) the refractive index is a significant parameter in optics that expresses the speed of
light inside the specified medium. (Luhar, et al., 2021) A multimode fiber propagates hundreds of light
modes at one time owing to its larger refractive index, while single mode fibers only propagate one mode.
(See figure 2) (Sawant, et al., 2014) However, the existence of multiple modes has a negative impact on
the quality of light being propagated through. (Luhar, et al., 2021) To solve this issue, multimode fibers
can be engineered to decrease the refractive index of the core to gradually increase from the center to
the edge. (Luhar, et al., 2021) These engineered fibers are called gradient index fibers or graded index
fibers. Therefore, these are used in the production of light transmitting concrete to optimize the quality
of light passing through to the other end.
4

Figure 2 Types of fiber optics (https://www.cables-solutions.com/three-common-types-of-fiber-optic-
cables.html)
In translucent concrete panels optical fibers are primarily used owing to their great light transmittance
properties, even at incident angles higher than 60˚. (Luhar, et al., 2021)
In light transmitting concrete panels, the optical fibers typically make up 4-5% of the volume of the entire
panel. This proportion is followed so that the translucent concrete block can retain its strength and
structural ability. (McGillivray, S. 2011). In existing projects or panels, the optical fibers used are either
glass or acrylic fibers and they essentially act as reinforcement in the panels. When the fibers run across
the thickness of the panel, they will have a higher compressive strength to take vertical loads applied to
it. This makes their compressive strength higher, ranging from 50 to 80 MPa, as found by Monika Zieliska
and Albert Ciesielski in their research. (Lampton, J., 2017) The overall process of placement of the optical
fibers is tedious and time consuming and requires skilled labor.
1.1.2 Cement
In light transmitting concrete, the most important material is the translucent element, and no special type
of concrete is required. Regular Portland cement with small or “fine” scale aggregates can be used. The
sand used in the cement should pass through a sieve with openings of 1.18mm and should not have any
larger impurities like stones. (Mishra, G., 2018) The cement mix is manually poured over the optical fibers
and allowed to set. A needle fiber is used for removing voids from the concrete, thus allowing better
compaction of concrete. (Kusuma S. et al., 2019)
5

1.2 History of Light transmitting concrete
The concept of light transmitting concrete has existed since the early 1900s, however, Aron Losonczi, a
Hungarian architect, introduced a more refined concept in 2001. (Concrete, S., 2020) While receiving
education at the Royal College of Fine Arts in Stockholm, Losonczi was experimenting with glass and
concrete to obtain a material that would combine the properties of both the materials: transparency of
glass and structural strength of concrete. (Zielińska, M., & Ciesielski, A., 2017) He was successfully able to
create a transparent concrete block within 2 years of putting forth the idea and the new material was
named LiTraCon; an abbreviation of ‘Light Transmitting Concrete’. (See figure 3) Losonczi’s manufacturing
process involved layering thousands of optical glass fibers and a concrete mix to create a homogenous
material. (Lampton, J., 2017) The architect received the RedDot Design Award for the development of the
material in 2006. (Zielińska, M., & Ciesielski, A., 2017)

Figure 3 Light Transmitting Concrete Wall (https://trends.archiexpo.com/litracon/project-150341-
214131.html)
1.3 Manufacture of Translucent concrete
The most common method known of the production of translucent concrete panels involves the use of
two basic materials, as mentioned earlier, concrete and the light transmitting fibers. German engineer,
Andre Roye developed a new way to place the optical fibers in the panels as compared to the existing
6

manual process suggested by Lasonczi. (Halbiniak, J., et al.) This process involved the production of a
transparent fabric like matrix made by pultrusion method. (See figure 4) (Halbiniak, J., et al.) The machine,
material and material structure can be seen. (See figure 5) The fabric then layered with cement in the
cement bath. This allowed the production process to be considerably easier and efficient thereby reducing
cost and allowing mass production. (Halbiniak, J., et al.) However, this process created a panel that could
only be used for decorative applications.

Figure 4 Machine that produces the fabric (left) and material structure (right) (Halbiniak, J., et al.)

Figure 5 Transparent fabric made by pultrusion (Halbiniak, J., et al.)
7

For the production of smaller pieces used for studies done by individuals, the process involves holes being
drilled in the plastic sheets (formwork) following the ratio of plastic optical fibers (POFs) in the panel.
(Luhar, et al., 2021) The POFs are placed manually in the slots of the formwork. (See figure 6) (Luhar, et
al., 2021) Lastly, the concrete mix is poured into the mold and then vibrated on a shaking table to remove
the air bubbles from the panel. (Luhar, et al., 2021)

Figure 6 Optical fiber arrangement (Luhar, et al., 2021)
Existing companies that involve themselves in the manufacturing of translucent concrete panels are few.
These companies have similar methods of production and use similar materials to manufacture these
panels. LiTracon LTD., LUCEM GMBH, Dupont Lightstone, LUCCON and Fapinex are the few companies
that are in the forefront of production. The manufacturing methods and finished commercial products of
these companies are elaborated upon in Chapter 2.
1.4 Properties of Light Transmitting or Translucent Concrete
1.4.1 Light Transmission
Many researchers have carried out tests on the light transmission of translucent concrete with varying
variables since there are no guidelines or standards established for its examination. (Luhar, et al., 2021)
Some studies state that light transmission property is directly proportional to the increase in optical fiber
ratios and their diameters. (Luhar, et al., 2021)
8

1.4.2 Durability
Concrete’s capability to resist deterioration caused by chemicals, abrasion, weathering, or extreme
environmental conditions while keeping its strength refers to its durability. (Luhar, et al., 2021) It is known
that glass is susceptible to ASR-alkali-silica reaction when exposed to alkaline environments. (Luhar, et al.,
2021) Pahliolico et al. have verified the durability of glass inclusions in Translucent Concrete in reference
to these kinds of environments. On the other hand, Pilipenko et al. have experimented on polymer epoxy
as the light transmitting material, for light permeability, color fade resistant, freeze thaw resistance, water
absorption and chemical resistance. (Luhar, et al., 2021)
1.4.3 Mechanical and physical properties
In the past, many tests to measure the mechanical properties of translucent concrete, analysis on the
flexural and compressive strengths have been carried out. (Luhar, et al., 2021) In research carried out by
Luhar et al. in 2015 to test the compressive strength of translucent concrete, it was reported that the
compressive strength of the translucent concrete panels was relatively similar to that of ordinary Portland
cement. (Luhar, et al., 2021) In the study, they used plastic optical fibers as the light transmitting element
of the diameter 1 mm that were placed at a distance of 8mm. these were integrated in a block of
dimensions 70 by 70 by 70 mm. Luhar et al. stated that the average compressive strength of the light
transmitting concrete with 5% optical fibers of the total volume was 36.70 MPa as compared to the 39.50
MPa Compressive strength of the standard concrete cubes. Therefore, it was apparent that translucent
concrete could be furthered in the use of structural construction. (Luhar, et al., 2021)
1.4.4 Energy savings
The property of translucent concrete that allows daylight to enter the building and illuminate it during the
day is sustainable. This allows a the reducing the amount of electricity used in a building. The range of
reduction of energy usage of 12.7 to 16% with light transmission as 5% in a building with translucent
concrete in its façade, was computed in simulations. (Mosalam, et al. 2013) (Luhar, et al., 2021) In this
9

computation research carried out by Mosalam et al., climatic conditions of Berkeley, California, United
States were used with a fiber optic proportion of 10.56%. More than a year’s simulation was carried out
to calculate the solar heat absorption of the panel. (Mosalam, et al. 2013) (Luhar, et al., 2021) A new
research by Ahuja and Mosalam in 2017 was carried out on thermal and lighting analysis to attain the
optimum ratio of optical fibers in the panels for highest energy savings. (Luhar, et al., 2021) They
developed a software that could perform the simulations and calculate the cooling and heating loads on
the heating, ventilation and air conditioning (HVAC) system to determine the optimum ratio of optical
fibers to achieve the best energy savings. (Luhar, et al., 2021) The research concluded that the use of 6%
of optical fibers in volume of the entire panel can reduce the total energy consumption of a building by
18%. (Luhar, et al., 2021)
1.4.5 Advantage and disadvantages of Translucent concrete
The apparent advantage of translucent concrete is that it allows natural daylight to enter a space without
costing money. Artificial light will be used for fewer hours of the day since the façade embedded with light
transmitting element will perform the said function. The optical fibers function as heat insulators by
transferring the heat into the mass of the building, thus are especially effective in regions with cold
weathers. (Luhar, et al., 2021) Translucent concrete facades also provide an interesting aesthetic to the
building. The light from the inside can make the building glow in the night. By providing LED lights on the
back end of the Translucent concrete panels, different hues can be transmitted to create interesting
patterns. The placement of the optical elements in the panels can also be done to illustrate different
words, symbols, and designs.
The translucent concrete market has been growing in the last couple of decades. However, there are only
a few companies that deal in the production of the material. The biggest disadvantage of the material is
the capital required in its production. Optical fibers are fairly expensive, increasing the cost of the end
product. A square meter of the material of 2.5 cm thickness costs about 740 euros. ((Zielińska, M., &
10

Ciesielski, A., 2017) Along with that, the production is tedious and requires skilled labor. Most companies
use hundreds of glass optical fibers in the that are expensive. There is also a lack of dependable
investigational information on the durability, mechanical properties as well as the service life of these
panels. (Luhar, et al., 2021) It can also be said that the replacement of one optical fiber in the case that it
gets damaged or discolored would be impossible. Thus, the development, investigation and testing on
this material needs to be furthered.
1.5 Defining Translucent Concrete for this research
For the basis of this research, translucent concrete can be defined as ‘a building material with light
transmitting properties owing to the inserted optical elements or apertures.’ The optical elements could
be used in the form of a reinforcement or mixed in with a cementitious mixture as aggregate. The light
transmitting material itself, its proportion and size could vary as per the function being performed by the
panel.
Translucent concrete, for the purpose of this research, can be categorized into 2 types. The first category
having light transmitting elements or materials and the second having openings that can allow light to
enter the interiors.
1.5.1 Light Transmitting Elements
Light transmission can be carried out by elements that allow light to be carried from one end to another
by the principle of light refraction and reflection. This means that the light passing through these elements
is reflected and refracted multiple times within the element with some loss in light intensity. This means
that the amount of light entering one end of the element is nearly equivalent to the amount of light
coming out of the other end. Some of these elements could include optical fibers – glass and acrylic,
extruded acrylic sheets and transparent resins or polycarbonates.
11

1.5.2 Openings
Windows typically perform the primary function of daylighting any interior space, which could be
misinterpreted to mean that large windows or openings can fall into the category of “Translucent
Concrete”. In these regular window walls, concrete is a secondary material and only functions to provide
a structural framework to house the windows. For translucent concrete to conform to its rule of allowing
light through, guidelines need to be set to that define the size of the openings that determines whether
they qualify as regular windows or ‘light transferring’ openings. Some of the materials to achieve this can
be glass or plastic bottles, bubble wrap, transparent resin, silicone jelly, glass straws, and glass or acrylic
capillary tubes.
Translucent concrete is a fairly novel material that uses light transmitting elements to provide daylighting
in an interior space during the day and makes a building glow in the night as the light from the inside is
transmitted out. The material also has great sustainable capabilities since it would reduce the amount of
energy used for electricity used for lights during the day. The fibers also act as an insulation material by
transferring the heat energy from the light rays coming through them into the thermal mass of concrete
rather than transfer it into the interior spaces of the building. This thesis defines what qualifies as
translucent concrete for the research. The following chapter will describe the work that is being done in
the realm of translucent concrete by individuals such as students, researchers, faculty as well as the
products, methods and materials being used by major retail companies.
12

Chapter 2
2. Literature Review
2.1 “Research and development of plastic optical fiber based smart transparent concrete” - Zhi Zhou Et
al.
The aim of this research was to create “smart transparent concrete” material using plastic optical fibers
(POF) and fiber Bragg grating (FBG). (Zhou, Z., et al., 2009) The main purpose was to reduce energy
consumption for lighting during the day by using sunlight. (Zhou, Z., et al., 2009) According to the authors
of the research, POF is a great medium to transmit light at certain wavelengths owing to the greater
refractive index of its core than in the coating. (Zhou, Z., et al., 2009) Total reflection is the mechanism
due to which light can be transmitted through these fibers. (Zhou, Z., et al., 2009) POF also has a much
larger core than common optical fibers. (Zhou, Z., et al., 2009) They can also transmit light at incident
angle as high as 60° without compromising on the amount of light passing through. (Zhou, Z., et al., 2009)
These fibers also have the advantage of greater ductility and flexibility in harsh environments.
The internal area ratio of POFs and the end surface roughness determines the light guiding performance
of the POFs in concrete blocks. (Zhou, Z., et al., 2009) The cement mixture was swapped out with epoxy
resin in order to reduce complexity of the experiment in the initial steps. (Zhou, Z., et al., 2009) Carbon
black was mixed with epoxy to increase its opacity and to ensure that any light detected was coming
through the POFs and not the epoxy. (Zhou, Z., et al., 2009) The block made had 4% of the area occupied
by POFs. (Zhou, Z., et al., 2009)
The mold for the epoxy-based block was made using metal sheets that were glued to make the formwork.
The end plates have openings that hold the POFs and are inserted into those perforated sheets. As seen
in the figures, the POF are bent so that the surface with the inlet of light is perpendicular to the outlet
surface. (See figure 7) This ensures that the light passing through the block is through the POFs and not
13

the epoxy portion of the block. It also proves the ductility of the material. Light can be seen passing
through the prototype. (See figure 8)

Figure 7 Fibers in the epoxy resin block mold (Zhou, Z., et al., 2009) (Left)

Figure 8 POF based epoxy resin block (Zhou, Z., et al., 2009) (Right)

Figure 9 Mold for Smart Concrete block (Zhou, Z., et al., 2009) (Left)
14

Figure 10 POF based Concrete block (Zhou, Z., et al., 2009) (Right)
Once the transparent concrete block was made, the light transmittance and heat conduction was tested
using visible light and infrared waves. (Zhou, Z., et al., 2009) The FBG was used as a sensing element to
test for load and temperature. (Zhou, Z., et al., 2009) The paper also examines the mechanical properties
of the material produced. (Zhou, Z., et al., 2009) However, these tests are not relevant since the scope of
this thesis is limited to the various materials and the production methods that are and can be used in the
production of translucent concrete.
The block made in the experiment also proves that light passes through the POFs that are integrated in
the blocks. The issue with this process is that the placing of the POFs is again labor and light intensive. The
amount of light passing through them depends upon the thickness of the POFs.
This research is interesting since we can see that even though the fibers are bent, light successfully passes
through them from one end surface to the other. The metal formwork being used for these small
prototypes of the concrete are very environmentally friendly since they can be reused repeatedly. This
adds on to the sustainable quality of the material.
15

2.2 “Preparation and study of resin translucent concrete products” - Juan, Shen, and Zhou Zhi (2019)
The goal of the research was to use resin as a translucent material in the production of a new ‘Resin
Translucent mortar-based concrete’ (RTMC). Transmittance, mechanical and thermal performance were
also tested on the block. The paper states that un-saturated polyester resin can transmit light as high as
94% while having the flexibility of being molded at room temperature and providing great thermal
transmittance. (Juan et al. 2019) The cost of resin is lower than optical fibers by almost 5 times, thus
reducing the cost of production considerably. (Juan et al. 2019) An optimum mix of mortar consisting of
PO42.5R Ordinary Portland Cement, river sand with a fineness modulus of 2.9, grade I fly ash and
polycarboxylic acid superplasticizer was achieved after multiple trials. (See figure 11) (Juan et al. 2019)

Figure 11 Mix ratio of mortar used
As compared to the complex and time-consuming process that uses plastic optical fibers, Juan et al. note
that the light guiding body can be produced at one time by molding it together using one mold. The entire
process of production of the RTMC involved 4 steps: manufacture of light guide body, manufacture of the
silicone mold, manufacture of light guiding body and the embedding cement mix. (Juan et al. 2019)
The light guide body produced has 16 light guide branches that have a diameter of 16mm connected by a
part that has a thickness of 9mm set in the middle. (See figure 12) (Juan et al. 2019) This mold is made
using plastic and wood.
16

Figure 12 Cube Prototype (Juan et al. 2019)
For the manufacture of the silicone mold, silicone and the curing agent are weighed and mixed in the ratio
of 100:2 and mixed rapidly for half a minute and poured into the mold. (Juan et al. 2019) The mold was
coated with a wax to facilitate the splitting of mold and the mixture of silicone and curing agent is allowed
to cure for four hours to make the lighting body. (See figure 13 and 14)

Figure 13 Devices for the silicone mold (Juan et al. 2019)

Figure 14 Fabrication of the silicone mold (Juan et al. 2019)
17

For the manufacture of the silicone mold, silicone and the curing agent are weighed and mixed in the ratio
of 100:2 and mixed rapidly for half a minute and poured into the mold. (Juan et al. 2019) The light guiding
body was made with resin and the accelerator mixed in a ratio of 100:8 and stirred. (Juan et al. 2019) A
curing agent was then added with a curing agent on the ratio of 100:1. (Juan et al. 2019) This was then
poured into the silicone molds until the holes were filled completely and then allowed cured for two
hours. (Juan et al. 2019) Once cured the light guiding body is removed from the mold. (See figure 15)

Figure 15 Resin Light Guide Body (Juan et al. 2019)
The Light guiding body was then placed in a steel formwork, followed by the pouring of self-compacting
sand mortar. (See figure 16) (Juan et al. 2019) a shaking table was used to allow the air pockets to be
vibrated out of the mortar mixture. (Juan et al. 2019)

Figure 16 Fabrication of RTMC block (Juan et al. 2019)
Once the concrete is allowed to set in the mold, the prototype is removed, and light is passed through
one end of the prototype. (Figure 17) This method was then used to make larger panels that were tested
on for light transmittance, compressive strength, and thermal performance. However, the method of
those tests is not discussed further in this research since they fall out of its scope.
18

Figure 17 Resin translucent concrete block (Juan et al. 2019)
The research produces 4 different elements that are being made at different stages of production with
different materials. This makes the process complex and lengthy. The materials used for the mold to make
the light guide body and the silicone mold are both wasteful. These molds cannot be reused. Instead of
creating the light guiding body as a separate element, a negative mold for the light guiding body could be
created using concrete itself. The silicone mixture that the light guiding body is made up of can be poured
directly into concrete mold, thus eliminating certain steps of the entire process, and also reducing the
material being used for the mold.
2.3 “Light Transmitting Lightweight Concrete with Transparent Plastic Bar” - Byoungil Kim
The purpose of the study by Byoungil Kim was to find a more efficient method of production of light
transmitting concrete in terms of constructability and cost. (Kim, B. 2017) The materials used for the
experiment in the research by Kim were acrylic pipes and rods with diameters ranging from 3 to 10 mm.
(See figure 18) According to Kim, these materials can be arranged in a formwork with a smaller labor force
and in a shorter time as compared to the existing optical fiber method.
19

Figure 18 Transparent acrylic rods and pipes (Kim, B. 2017)
The concrete mix excluded coarse aggregate to prevent the phenomenon of fiber balling and to allow
better flowability through the narrow gaps between the transparent materials. (See table 1) (Kim, B. 2017)
Table 1 Cement Mix Proportions in kg/m3 (Kim, B. 2017)

The production process started with the preparation of the acrylic rods to 110 mm length. The stainless-
steel mold was drilled with different sized holes of 3,5 and 10mm and the advantage with these types of
molds is that they can be taken apart after the cement mixture has dried and reused to make another
piece.(See figure 19) (Kim, B. 2017)

Figure 19 Different molds (Kim, B. 2017)
20

The acrylic elements are then placed between the two stainless steel sides with holes and concrete is
poured over it to form the light transmitting block. The prototype was then completed by cutting it do
desired thickness after allowing it to cure underwater for 28 days and after allowing it to set for 24 hours
in the mold. (See figure 20) (Kim, B. 2017) Different colors of light are passed through the prototypes to
see the light transmitting through the panel. (See figure 21)

Figure 20 Production process (Kim, B. 2017)

Figure 21 Finished product with different light sources (Kim, B. 2017)
Kim states that the transmission of light was found to be exceptional in all the materials and diameters,
in particular with the smallest diameter of the acrylic elements due to the dense array of a larger number
of elements. Grinding the surface of the finished blocks with the acrylic rods and pipes also enhanced the
quality of light coming through the blocks. (See figure 22) (Kim, B. 2017)
21

Figure 22 Visual object effect before and after surface treatment (Kim, B. 2017)
2.4 Manufacturers of Translucent Concrete
The market for translucent concrete in terms of production is still in a nascent phase. There are about 5-
6 manufacturers that solely focus on the production and design on this material in form of panels for
indoor and outdoor use, lamps and jewelry. When looked at in depth, most of these companies have
comparable methods of production, use similar materials and have similar outcomes in terms of panels
used for facades and enclosures of buildings.
2.4.1 LiTraCon LTD
Aaron Losonczi, one of the first successful producers of light transmitting concrete, developed the first
light transmitting material in 2001 and patented it 2002. He founded the company LiTraCon Kft. in 2004
located in Csongrád, Hungary.
22

Figure 23 The Garden Pavilion (http://litracon.hu/en/references/20)

Figure 24 The Garden Pavilion (http://litracon.hu/en/references/20)
The company deals with manufacture and sale of three main light transmitting concrete products –
LiTraCon Classic, LiTraCon pXL and the Litracube Lamb. LiTraCon Classic was the first commercially
available translucent concrete block. (See figure 25) It comprises of optical fibers and fine concrete and is
entirely handcrafted making each piece unique.

Figure 25 LiTraCon Classic (http://www.litracon.hu/en/products/litracon-blokk)
23

The LiTraCon pXL uses a specially formed and patented plastic units using an industrialized manufacturing
method that makes this type more affordable. (See figure 26) The distribution of the plastic units is regular
or follows a linear pattern as compared to the organic distribution in the Classic type. However, on
demand the patterns and colors can be customized as per the need of the client.

Figure 26 LiTraCon pXL (http://www.litracon.ca/en/references/21)
The LitTaCube Lamp is an illustration of the innovative applications of the concept of light transmitting
concrete. (See figure 27) The lamp is made using glass optical fibers and can also be customized as per
client’s specifications.

Figure 27 LiTraCon pXL (http://www.litracon.hu/en/products/litracube-lampa)

24

Table 2 LiTraCon product specification
Specification LiTraCon Classic LiTraCon pXL LitTaCube Lamp
Translucent
ingredient
Glass optical fibers Glass plastic units Glass
Format* 1200 x 400 mm 1200 x 600 mm - 40mm thk
3600 x 1200 mm – 60 mm
thk
175 x 175 x 221mm
Thickness* 25 – 500 mm 40 mm, 60 mm
Colors* White/ grey/ black White/ grey/ black
Application Indoor and outdoor Indoor and outdoor Indoor and outdoor
Surface Polished Molded, washed, polished

2.4.2 LUCEM GMBH
The company was founded in 2007 at RWTH Achen university by Dr. Andreas Roye. Lucem provide full
installation solutions for indoor and outdoor illumination. (Auflage Juli, 2019 - LUCEM Brochure) LUCEM
has been in cooperation with Holcim Germany since June 2019 to optimize the production of their panels
and further their research for translucent concrete products. (Auflage Juli, 2019 - LUCEM Brochure)
LUCEM is accountable for design and technology and Holcim is concerned with finding the appropriate
concrete mix for production process. (Auflage Juli, 2019 - LUCEM Brochure) Holcim EcoFlow is a special
binder that has been developed by Holcim to be used specifically in LUCEM products. (Auflage Juli, 2019
- LUCEM Brochure) These binders need to be highly free flowing to allow smooth movement between the
filigree glass optical fibers. (Auflage Juli, 2019 - LUCEM Brochure)
25

Figure 28 Lucem Lichtbeton Panels (https://www.bft-
international.com/en/artikel/bft_Smooth_translucent_concrete_presented_for_the_first_time_342041
9.html)
In a report by LUCEM Ltd. from 2011, the concrete mix used in their translucent applications is a mixture
of cement, pigments and sand in which sand makes up 50% of the volume of the mixture. The color
pigmentation is added using ferric oxides. There were 3 concrete mixtures offered by LUCEM according
to the 2011 report: Ulmer White, 3mm grain; Grey Calcilith, 3mm grain and Anthracite Calcilith, 3mm
grain. (See figure 29) The surfaces of these panels are generally polished to give a smooth and finished
appearance to the panels.

Figure 29 Ulmer White; Grey Calcilith, and Anthracite Calcilith (From left to right)
From LUCEM report from 2011 (https://www.stylepark.com/en/lucem/lucem-starlight)
The company makes 3 different light transmitting façade panels – LUCEM Starlight, LUCEM Line, and
LUCEM Label. The LUCEM Starlight is based on selective translucency which means that optical fibers are
placed organically in the panel and have different diameters. (See figure 30) This type gives an impression
of a starry sky and has a three-dimensional luminosity. (Auflage Juli, 2019 - LUCEM Brochure)
26

Figure 30 LUCEM Starlight (https://www.stylepark.com/en/lucem/lucem-starlight)
The LUCEM Line uses optical is created by embedding optical fibers in the concrete in a linear form. (See
figure 31)

Figure 31 LUCEM Line (https://www.stylepark.com/en/lucem/lucem-starlight)
The Lucem Label line is the solution for clients that looking to create images, numbers, logos, lettering,
relief. (See figure 32) These can be handcrafted in a positive (luminous) and negative (blind) way to create
sophisticated design. (LUCEM, 2020)

Figure 32 LUCEM Label (https://www.stylepark.com/en/lucem/lucem-label)
All the panel types made by LUCEM can either be used as a façade material allowing daylighting in the
structure during daytime or as wall or floor panels that would need to have artificial light sources from
behind the panel for light to pass through. The light sources used can vary in color and brightness
depending upon the requirements and goals of the project.
27

Table 3 Technical specifications of the different panel types
*Can be personalized upon request
Specification LUCEM Line LUCEM Starlight
Translucent ingredient Glass optical fibers Glass optical fibers
Format* 1200 x 600 mm; 1600 x 600 mm 1200 x 600 mm
Thickness* 20 mm; 30 mm 30 mm
Colors* White/ dark grey/ grey White/ dark grey/ grey
Application Indoor and outdoor Indoor and outdoor
Surface Matt satin finished Formwork plain
Texture Fine-grained concrete matrix
and optical fibers in linear
structure
Irregular pattern of fiber optics
with varying diameters
Number of fibre optics per m
2
200 500
Diameter of optics 0.5 mm 1,2,3 mm

2.4.3 Dupont Lightstone
In 2006, Christoffer Dupont, an engineer by trade, made a successful prototype of a small translucent
concrete panel and eventually started his Company Dupont Lightstone.
(http://dupontlightstone.com/om.html) Since then, the company has moved on to producing facades that
can display live images on its surfaces. (See figure 33) (Dupont Catalog) This new digital signage technology
can have applications in floors, sidewalks, interior walls, or facades and works due to the carefully placed
fiber optics in concrete. (Dupont Catalog)
28

Figure 33 Dupont Lightstone LED screens (http://dupontlightstone.com/om.html)
The specially developed optic light guides embedded in the concrete allow a live image to be transmitted
through the concrete. (See figure 34) These screens consume little energy since they use LED light while
having a long-life span and requiring low maintenance. (Dupont Catalog) All Dupont products can be
designed to color and surface texture specifications but thickness ranges from 25 mm to 50 mm.

Figure 34 Cross-section of Dupont LED panels (Dupont Catalog)

2.4.4 Luccon
The company was established in 2004 and since then been one of the leaders in production of translucent
concrete. The concrete used for LUCCON translucent concrete panels consists of 10 different elements
and can be considered as high-performance concrete (HPC) or ultra-high-performance concrete (UHPC).
29

(See figure 35) (LUCCON Information Brochure) The granularity of the concrete mix used defines the
characteristic of the mixture as well as its visual appearance. (LUCCON Information Brochure) The color
of the mix can also be changed by adding colored granite granulates. It is suggested that high density
aggregates are used in the concrete mix used for panels that are used outside or as floors since they
prevent dirt absorption. (LUCCON Information Brochure) The company uses CNC machines in the surface
treatment of their panels.

Figure 35 LUCCON Translucent concrete panels (https://design-milk.com/luccon-transparent-concrete/)

The optical fibers that are used by LUCCON comprise of the core, reflective shell and protective cover.
(See figure 37) These range in diameter from 0.4 to 0.7 mm and the thickness of panel ranges from 20 or
30 mm. The available sizes are 12000 x 1000 mm or 2000 x 1000 mm with 300 optical fibers per meter
square and come in standard colors – white, grey and black. (LUCCON Information Brochure)

Figure 36 Steps made using LUCCON translucent concrete (https://design-milk.com/luccon-transparent-
concrete/)
30

Figure 37 Optical fiber composition used by LUCCON (http://www.luccon.com/en/product/)

2.4.5 Fapinex
Fapinex is Façade Engineering and Design company in the Middle East that designs and supplies
personalized façade systems including Translucent concrete panels. These translucent concrete panels
are produced in Germany can can be used in various different applications. (See figure 38)

Figure 38 Translucent concrete panels (https://www.fapinex.com/products_details/light-transmitting-
concrete)

These panels are available in dimensions: 1200 x 600 mm and 1600 x 600 mm; with thicknesses ranging
from 15, 20 and 30 mm. These are available in Anthracite and White colored panels with optical fibers.
(See figure 39)
31

Figure 39 Translucent concrete with optical fibers (https://www.fapinex.com/products_details/light-
transmitting-concrete)
2.4.6 Others
Apart from these 5 major companies, there are a couple of more precast concrete companies that are
involved in the production of Translucent concrete panels. Italcementi SPA, Pan – United Corp. Ltd., Beton
Broz, Florack Bauunternehmung GMBH, Illuminart and Rocalite are a few such companies. There is not
much information regarding the materials and the processes provided by these companies.
2.5 Morphology Study:
To understand what type of materials can be used in a more efficient process of production of translucent
concrete panels, a morphological study of existing applications of translucent concrete is useful.
2.5.1 Al Aziz Mosque, Abu Dhabi
The translucent concrete paneling system used in the Al Aziz Mosque was provided by a German
manufacturer, LUCEM. The glass optic fibers used in the project were placed in accordance with the text
provided by the expert calligrapher through architectural drawings. (Stott, R., 2017) The facade spanned
515 square meters consisting of 207 panel elements of approximately 1800 x 1400 x 40 mm each. (See
figure 40) (Concrete, S. 2020) The weight of one such panel would be around 300kg.
32

Figure 40 Al Aziz Mosque (https://inhabitat.com/unique-light-transmitting-concrete-makes-abu-dhabis-
gorgeous-al-aziz-mosque-glow/)

To blend the translucent concrete panels with the stone panels used elsewhere in the project, the
concrete used was color pigmented to match the color of the stone as well as sandblasted to match the
textures. (Stott, R. 2017) LED lights are installed behind the facade panels that are activated after sundown
and this light is transmitted to the outside via the fiber optics.
2.5.2 Stuttgart City Library in Germany
The project Designed by Yi architects involves use of a seamless 9 by 9 grid of frosted glass blocks that are
encased in a wall of concrete wall. (See figure 41) (Prizeman, O., 2020)

Figure 41 Stuttgart City Library Façade
33

2.5.3 Cella Septichora/Pecs, Hungary
Prefabricated LiTraCon panels measuring 361 x 244 x 10 cm set in a steel frame were used in this project.
Glass optical fibers were used to make the panel that allows light to transmit light through the panel. (See
figure 42)

Figure 42 Cella Septichora
2.5.4 Mont Blanc, Tokyo

Figure 43 Mont Blanc Façade panels (https://slidetodoc.com/ron-losonczi-npp-annual-conference-
reykjavk-11-th/)
34

Litracon panels measuring 600 x 300 x 30mm were used to create a freestanding sculptural element at a
flagship store for Montblanc. (See figure 43) These panels have a thickness of 30mm or 3cm that seems
to transmit light better than through a thicker panel.
2.5.5 Italian Pavilion at the Shanghai Expo in 2010
Newly developed cement-based material by Italcementi was used to build the pavilion which is called
i.light®. 3,774 transparent panels were used which made up 40% of the structure allowing the structure
to be daylit. (New Atlas., 2015) The material does not use fiber optics such as that used in most translucent
panels. Researchers at Italcementi have made this material using cement and plastic resin admixtures.
These panels serve the purpose of daylighting, due to the shading and light scattering techniques and
thermal insulation, due to low conductivity of the plastic component. (See figure 44) (New Atlas., 2015)

Figure 44 Italian Pavilion facades (https://www.heidelbergcement.com/en/italian-pavilion-shanghai)
The mixture is reported to bond well with thermoplastic polymer resin that is inserted into a formwork
with 2-3 mm holes running across the width of each panel. (New Atlas., 2015) There are approximately 50
holes in each 500 x 1000 x 50 mm (19.7 x 39 x 2 inch) panel, resulting in an overall transparency of about
20%. The pavilion also comprised of semi-transparent panels with a 10% transparency of created by
35

“modulating the insertion of the resins”. (New Atlas., 2015) The thickness of this panel is 50 mm or 5 cm
which like the panels in Mont Blanc project, have a considerably low thickness allowing light to pass across
the panel more efficiently.
2.5.6 Bathing Hall at Obermain Therme in Bad Staffelstein, Germany
The structure is a total of 200 square meters made of LUCEM and contains around 2 million optical fibers,
which transmits the LED light to the surface. (See figure 45) (Hill, 2017) The panels are 20 mm thick,
installed with KEIL undercut anchors. (Hill, 2017) According to LUCEM, transparent polycarbonate spacers
in 2 cm thickness inserted between the steel frame and the light transmitting concrete panels. (Hill, 2017)
This was done to reduce the shadow of the frame. (Hill, 2017) The panels were filled with epoxy resin to
ensure longevity of life in the atmosphere of high humidity and salinity. (Hill, 2017)

Figure 45 Bathing Hall structure (https://www.world-architects.com/en/architecture-news/products/a-
salt-crystal-made-with-lucem-translucent-concrete)

2.5.7 Iberville Veterans Memorial
The Memorial has translucent elements that are produced by LiTraCon, thus uses glass fibre optics to
transmit light from the inside to the outside. (See figure 46)

36

Figure 46 Iberville Veterans panels (http://www.litracon.hu/hu/referenciak/30)
2.5.8 New Headquarters of Bank of Georgia
Year: 2011
Architects: Architectural Group & Partners, Tbilisi
The panels used in this interior application was the LUCEM Line which has panels with dimensions 120 x
60 x 15 cm. (See figure 47) (Furuto, A., 2017) Light is transmitted from the thousands of embedded optical
fibers and the source of light is fluorescent tubes within the panels. (Furuto, A., 2017)

Figure 47 Interior Panels (https://www.archdaily.com/228934/new-headquarters-of-bank-of-georgia-
illuminated-translucent-concrete-for-interior-design-architectural-group-partners)
2.5.9 RWTH Aachen University
Completed: 2012
Architect: Carpus+Partner AG, Aachen
37

The installation spans a total of 60 square meters and is composed of LUCEM panels measuring 120 x 50
x 2 cm. (Hill, 2014) RGB LEDs with DMX control that lights the facade with a range of color variability and
control. (See figure 48) (Hill, 2014)

Figure 48 LED façade panels at RWTH Aachen https://www.architectureanddesign.com.au/news/world-
s-first-light-transmitting-concrete-facade#
2.5.10 Wahat Al Karama
Location: Abu Dhabi, UAE
Architect: MIRAL
Lucem panels that are made up of glass fiber optics are used in the flooring tiles in the memorial. (See
figure 49) The LED lights placed below the surface shine through the optical fibers during nighttime.
38

Figure 49 Light transmitting elements on floor (https://lucem.com/works/memorial-abu-dhabi-uae/ )

2.5.11 Martyr’s Memorial & Museum
Architect: ParadigmDH
The memorial used a LUCEM panels with LED lights placed inside the boxes to allow light to shine through
displaying the light pattern created by the glass fiber optics. (See figure 50) (Ideal Concepts Co., 2017).

Figure 50 Light element in translucent (https://lucem.com/translucent-concrete/lucem-label/)

39

2.5.12 Nino Arabella
Completed: 2014
Architect: Jassim Alshehab Architects
The project uses thin light weight LUCEM panels that contain glass optical fibers to transmit light into the
interior spaces. (See figure 51)

Figure 51 Translucent panels (https://lucem.com/works/nino-arabella/)
2.5.12 Capital Bank branch, Amman
Completed: 2018
Architect: ParadigmDH, Amman
The encasing of the stairwell is made up of 14m LUCEM concrete panels that have fiberglass optical fibers.
This allows for light to flow into the stairwell during the day and to make the stairwell glow during the
nighttime when it is lit. (See figure 52) (Lucem GmbH, 2018) the panels are 30 mm thick and are mounted
on a steel structure above undercut anchor. (Lucem GmbH, 2018)
40

Figure 52 Light transmitting panels on the staircase (https://www.archdaily.com/902421/capital-bank-
of-jordan-paradigm-dh)
2.5.13 NEO - Concrete Bubbles, 2018

Figure 53 Interior Panels https://www.designboom.com/architecture/translucent-concrete-bubbles-
tengbom-butong-sweden-10-28-2018/
Architect: Tengbom
Product: Translucent Concrete Panels
The concrete panels incorporate bubble wrap into the formwork resulting in a grid of concave like
indentations with small membrane perforations that allow light to pass through. (Hill, 2018) The LED light
behind and in front of the panel allow the panels to emit different colours. (Hill, 2018)
41

Figure 54 Construction process (left) and Detail (right)
https://www.designboom.com/architecture/translucent-concrete-bubbles-tengbom-butong-sweden-
10-28-2018/
2.5.14 Breezeblock House
Year: 2020
Architects: Tamara Wibowo Architects
The transparent enclosure is formed by the secondary skin made up of cement blocks that have voids in
them; these are custom designed with protruded Corten frames around a series of openings throughout
the house. (See figure 55) (Abdel H., 2021) These blocks serve primarily 2 functions: a passive cooling
strategy as well as reducing visual connection of the house from the inside to the outside. (Abdel H., 2021)

Figure 55 Breezeblock screen (https://www.archdaily.com/951058/breeze-blocks-house-tamara-
wibowo-architects)
42

2.5.15 Dutch Design Week in Eindhoven
The temporary structure is made of three Zospeum sandwich-panels measuring 3600mm 1200mm x
320mm. (See figure 56) (Zospeum, 2016) The translucent aggregate is glass optical fibers. (Zospeum, 2016)
The production method involved the poring of a concrete mixture on the optical fibers placed in a wooden
formwork. (See figure 57)

Figure 56 Zospeum Installation (https://archello.com/product/zospeum)

Figure 57 Production method at Zospeum (https://metropolismag.com/products/clear-breakthrough-
zospeum-takes-translucent-concrete-next-level/)
43

2.5.16 Plastic bottle School in Philippines
The school was built by the My Shelter Foundation in Partnership with Pepsi in the Philippines. (Keiren,
K., 2016) It used 9,000 used plastic bottles and cement as binding material. (See figure 58) (Keiren, K.,
2016)

Figure 58 School interiors (left) and Production method (Right) (https://insteading.com/blog/plastic-
bottle-schools/)

Figure 59 Plastic bottles from inside during construction method (https://insteading.com/blog/plastic-
bottle-schools/)
2.5.17 Signal Iduna, Dortmund

Figure 60 Fig. Elevator panels – LUCEM Line (https://lucem.com/works/signal-iduna-dortmund-
germany/)
44

The project uses the panels made by LUCEM to form a seamless light wall cladding that gives an impression
of glow from within. 9 panels set in a special framework with dimensions of 1200 x 3500 mm were used.
(See figure 60)
2.5.18 Earthships, Taos County
The earthships of Taos County built by Mike Reynolds are low-cost shelters that are entirely sustainable
and self-sufficient. Weideman, P. (2016) The structures are made up of rammed earth encased in a steel-
belted rubber. Weideman, P. (2016) Recycled glass and plastic bottles are used for aesthetics and to allow
light to enter the structure, thus eliminating the need for artificial daylighting. (See figure 61) This is an
interesting that fits the “aperture” version of translucent concrete that has been used in smaller projects
throughout the world.

Figure 61 Inside of Mike Reynold’s Earthship
(https://www.santafenewmexican.com/pasatiempo/columns/art_of_space/gimme-sustainable-shelter-
the-earthships-of-taos-county/article_1beac6f9-0a4a-5cac-a109-7dff1aea97a3.html)
45

2.6 Conclusion
Creating the morphology allowed the information to be organized in a better way to understand the
materials being used in the existing projects of translucent concrete. The thickness of the panels varies
from 15 cm to 3 cm. From the images of these projects that show the light passing through these panels,
it can be inferred that the thinner panels allow light to pass through more efficiently across the panels. In
thinner panels, the number of times that the light rays reflecting and refracting through the fibers.
From Table 4, we can see that acrylic and glass fibers are the main materials that are used in the
translucent concrete applications all over the world by major companies as the translucent aggregate in
the panels. Acrylic and glass fibers create more sophisticated translucent concrete material as compared
to glass or plastic bottles placed in a mortar mixture. Using fibers also allows for precast translucent
concrete panels to be made according to specifications and design requirements. However, the process
of production of these panels requires immense skilled labor, advanced technology and machinery, is time
consuming and can be extremely expensive. On the other hand, the use of plastic and glass bottles can be
considered more vernacular in nature and can be very flexible. Skilled labor may not be required for the
production of walls using these bottles. They can be done for cheap as well as requiring less time to do
so. Since these bottles are larger in size than acrylic fibers or glass fibers, they allow more light to enter a
structure and give a more rustic feel to the structure. This also shows that research is limited to these
materials and there has not been extensive research for alternative methods that can be used for
furthering the use of this sustainable material.
46

Table 4 Translucent Concrete Morphology
Project Name
Architect/
Contractor
Applicatio
n Type
Translucent
Material
Parent
Material
Thickness
of Panel
Dimensions
of Panel
Al Aziz
Mosque, Abu
Dhabi
Lucem - APG
Architecture
and Planning
Group
Exterior
Panels
Acrylic
optical Fiber
Pigmente
d
concrete 70 mm
1800 x 1400
mm
Stuttgart City
Library in
Germany Yi architects
Double
Wall
9 x 9 frosted
glass bricks Concrete
Not
Available
Not
Available
Cella
Septichora/Pec
s, Hungary Litracon
Exterior
Panels
Acrylic
optical Fiber
In Steel
Frame 100 mm
3610 x
2440 mm
Mont Blanc,
Tokyo Litracon
Free-
standing
sculptural
element
Acrylic
optical Fiber Concrete 30 mm
600 x 300
mm
Italian Pavilon
at the Shanghai
Expo 2010
Cement-
based
material by
Italcementi
Exterior
Panels
Rectangular
shaped
plastic resins
-
thermoplast
ic polymer
resin
Cement-
based
material 50 mm
1000 x 500
mm
Breezeblock
House - &
others
Tamara
Wibowo
Architects
Concrete
masonry
screen
walls Air Mortar
Customizabl
e
Customizabl
e
Glass bottle
walls - & others
Exterior
mainly
Recycled
Glass Bottles Concrete Varies Varies
Bathing hall at
Obermain
Therme LUCEM
Sculptural
element
Acrylic
optical Fiber
In Steel
Frame 20 mm Varies
New
Headquarters
of Bank of
Georgia
LUCEM -
Architectural
Group &
Partners,
Tbilisi Interior
Acrylic
optical Fiber Concrete 150 mm
1200 x 600
mm
RWTH Aachen
University
LUCEM -
Carpus+Partn
er AG, Aachen
Exterior
Panels
Acrylic
optical Fiber Concrete 20 mm
1200 X 500
mm
Wahat Al
Karama MIRAL Flooring
Acrylic
optical Fiber Concrete
Not
Available
Not
Available
Martyr’s
Memorial &
Museum
LUCEM -
ParadigmDH
Sculptural
element
Acrylic
optical Fiber Concrete
Not
Available
Not
Available
47

Capital Bank
branch Amman
LUCEM -
ParadigmDH
Exterior
Panels
Acrylic
optical Fiber Concrete
Not
Available
Not
Available
NEO - Concrete
Bubbles Tengbom Interior Bubble wrap Concrete
Not
Available
Not
Available
Dutch Design
Week in
Eindhoven Zospeum Panels
Acrylic
optical Fiber Concrete 320mm
3600mm
1200mm
School in
Philippines Locals
Exterior
Wall
Plastic
bottles Mortar
Not
available
Not
available
Signal Iduna,
Dortmund LUCEM
Interior
décor
Acrylic
optical
fibers Concrete
Not
available
1200 x 3500
mm
Earthship
Mike
Reynolds
Exterior
Walls Glass bottles Concrete
Not
available
Not
available

48

Chapter 3
3. Methodology
The research comprises of 5 different methods that are explored and documented as alternatives to using
glass optical fibers as the element that transmits light. The process of the production of these translucent
glass panel prototypes will be dependent on the material being used as the medium of light transmittance.
Every material chosen will require unique molds and varying formworks but will use similar concrete
mixes. A small experiment will be carried out to understand the flowability of concrete before testing
different light transmitting element materials. To test the light transmittance, the method of placement
of the translucent aggregate and the durability of the translucent materials chosen, small-scale test
samples will be made. 6 test cases will be carried out with the following translucent materials: GFRC Glass
fibers, acrylic fibers, glass capillary tubes, Plastruct clear rods, PETG 3D printed network and epoxy resin
network. (See table 5) These materials were selected since they fit the category of translucent concrete
without having large openings in the panel. They also cause light to be transmitted from on end to another
without too much dispersion of light. These materials also provide great potential of better placement of
the translucent aggregate in the molds.
Table 5 Materials experimented
Translucent Material Methods involved
GFRC Fibers Winding over nails
Acrylic Fibers Winding over nails
Plastruct rods Manual placement in form
Glass Capillary Tubes Manual placement in form
PETG 3D printer filament 3d Printing and manual placement in form
Epoxy Resin 3d and manual placement in form
49

3.1 Experimenting with concrete flowability
To understand the flowability of concrete mixture without any large aggregate, Quikrete cement will be
used for this experiment. Quikrete is the largest manufacturer of packaged concrete and is the most
widely available concrete mixes in the United States. (See figure 62) This company was chosen since the
material is easy to obtain and that it has a short setting time. The website of Quikrete says that it sets in
20 to 40 minutes with a compressive strength of 6000 psi and this would allow more prototypes to be
made testing different methods and materials. The fast-setting time of Quikrete is owed to certain
additives in the cement mixture that the company does not divulge. The website also mentions that even
though the set time of Quikrete is short, to reach is full compressive strength the mixture takes about a
month. In addition to the quick setting time of Quikrete, the material is fairly similar to concrete and at a
smaller scale mimic the properties of concrete used in large scale uses of concrete.

Figure 62 Quikrete “Concrete Patching Compound”
By carrying out this experiment of flowability, it will be easier to understand the behavior of Quikcrete
when being poured into formwork that has either fiberglass or similar materials for the prototypes. The
behavior of this Quickrete mixture can be expected to have similar flowability characteristics as regular
concrete with smaller aggregate that will be used in production of larger scale translucent concrete
50

panels. The concrete mixture will have to differ owing to the kind of light transmitting elements embedded
in the prototype.
The experiment with fiberglass used in GFRC panels will require a Quikcrete mixture that is thin and flowy
owing to the brittle nature of the fiberglass. This will avoid the fiberglass from breaking due to the weight
of the concrete.
Prototype 2 and 3 which are acrylic fibers and Plastruct rods, the Quikrete mixture can be thick and made
using the ratio mentioned in the instructions. Since both these materials are thick, strong and malleable,
they can take the weight of a thick concrete mixture.
Glass capillary tubes used in prototype 4, will need a thin mixture since they can be brittle and delicate
owing to their parent material.
With Prototype 5 and 6 that are 3D printed network and the epoxy resin network, the Quikrete mixture
can be thick since these networks will be placed in the concrete layer by layer. This means that one layer
of the Quikcrete mixture will be poured into the formwork, a layer of the network will be placed on the
layer of concrete and this process is iterated until desired height of the prototype is met.
For the experiment to understand the flowability of Quikcrete, 5 parts of this cement will be mixed with
1 part of clean water and mixed until there are no lumps in the mixture.
For a basic formwork will be made manually by cutting foam core with the dimensions (see figure 63) and
made into a formwork. Certain adjoining faces will have openings to allow concrete to flow from one
hexagonal opening to another. This will create a mold for concrete to be poured into it.
51

Figure 63 Mold geometry
3.1.2 Exploring with 3D Geometries
The first method explores different 3D configurations using a honeycomb pattern. (See figure 64) This
method would fall in the category of creating small openings in the wall. These prototypes were planned
to use 2 materials: Concrete mix and acrylic formwork that would allow light to pass through.
1. 2. 3. 4. 5.

Figure 64 Prototypes of 3D Geometry alternatives
3.2 Fiberglass used in GFRC panels
Glass fiber reinforced concrete (GFRC) is a type of precast concrete that has chopped pieces of fiberglass
mixed in the mixture to increase its structural strength. This fiberglass used in GFRC usually comes in the
form of a large yarn and is called ‘Assembled glass roving”. This fiberglass material has not been explored
52

as a material that can be used for light transmission in translucent concrete. To realize this proof of
concept, a study will be done using GFRC fiber in looping around an outer wooden formwork. The test
prototype will be of the dimension 8” by 4” by 3” with the translucent elements running from one 8” by
3” face to the one across.
This formwork is made using wooden pieces with dimensions. (See figure 65) On the base wooden piece,
the pieces of the formwork that make up the sides of the form will be nailed. The pieces that make up the
longer side of the form will hold the optical fibers. Therefore, this piece is divided into two pieces so that
the fibers will be held between the two. After these pieces are nailed in, a set of nails that the optical
fibers will be wound around will be nailed on either side of the long side of the prototype. These nails will
be placed 0.5cms apart. (See figure 65)
The looping of fibers will be done in different looping configurations to see the difference between the
light transmission through the different looping configurations. The loops will be done in the
configurations of 10, 30 and 50 loops. Since there are 15 nails in total, allowing there to be 15 loops, every
5 loops will have one configuration, which means that the first 5 nails will have 10 loops, the next 5 will
have 30 loops and the last 5 will have 60 loops of the GFRC fibers. Once the fibers are wound around the
nail following the looping configurations, the top piece will be put on the fibers so that they are held in
place. This piece will either be nailed or glued on the bottom piece.

Figure 65 Formwork dimensions in plan (left) and section (right)
53

The formwork will be coated with a cooking spray to ensure easy removal of the prototype from the
formwork and will be ready to have the concrete mix poured in it. For these experiments, Quikrete will
be used with water. Five parts of this cement will be mixed with 1 part of clean water and mixed until
there are no lumps in the mixture. This will then be poured into the formwork that is placed on a vibration
table. This will ensure that the air bubbles from the concrete formwork are removed.
The prototype is then kept aside and allowed to cure for 2 days to ensure the strength on concrete is
reached. The wooden formwork is taken out first, the fibers coming out of the prototype and winding
around the nails will be cut using nail clippers to get as close to the concrete surface as possible. The
prototype will be removed from the base and then polished to have a smooth surface.
3.3 Acrylic Fibers
Acrylic fibers are used in the commercial production of translucent concrete panels. These are placed in
the concrete in the form of a knit fabric making the process easier. This experiment has been done to
understand the materiality of the panels and to see how light is transmitted through these elements.
The process of making the prototype is fairly similar to the process of the prototype using fiberglass. The
test prototype will be of the dimension 8” by 4” by 3” with the translucent elements running from one 8”
by 3” face to the one across. This formwork is made using wooden pieces with dimensions (See figure 66).
On the base wooden piece, the pieces of the formwork that make up the sides of the form will be nailed.
The pieces that make up the longer side of the form will hold the fibers. Therefore, this piece is divided
into two pieces so that the fibers will be held between the two. After these pieces are nailed in, a set of
nails that the fibers will be wound around will be nailed on either side of the long side of the prototype.
These nails will be placed 0.5cms apart (See figure 66).
54

Figure 66 Formwork dimensions in plan (left) and section (right)
Looping will be done in the following system: 1
st
3 nails: 1 loop; next 3 nails: 2 loops; next 2 nails: 5 loops
and the next two: 8 loops. The rest of the next 4 nails have looping that go diagonally across. The 4 nails
will be labeled: A, B, C, D on one side and following that, the nails that run straight across are labeled the
same respectively. One side will be labeled 1 and the other will be labeled 2. (See table 6)
Table 6 Diagonal looping configuration
Side 1 Side 2
A C
B D
C B
D A

The concrete mixture is prepared by mixing 5 parts of Quikrete and 1 part of clean water in a bucket. The
mixture is mixed thoroughly to remove any lumps from the mixture and allow smooth flow of the mixture
55

into the formwork. The mixing process is essential since the lumps could get stuck in the fibers making
the process difficult. It is possible for the concrete to overflow onto the top of the sides of the formwork.
Once the concrete is poured into the formwork, the base is tapped by hand continuously for 5 minutes to
remove any air bubbles from the prototype.
The concrete will be allowed to set in the formwork for 2 days. A nail clipper will be used to cut the fibers
from the nails from either side. The nails on either side will then be taken out using a hammer and the
longer pieces of the formwork remaining are removed. The prototype will then be separated from the
base plywood piece. The remaining protrusions of the fiber glass were cut using nail clippers to get as
close to the block as possible and the prototype will be ready.
3.4 Plastruct rods
Acrylic as a material is known to be good for light transmission and this experiment was done to
understand the performance of a thicker acrylic material in light transmission. The Plastruct rods used for
the experiment are of the diameter of 1/16” and is made of clear acrylic material. These rods were ordered
from Amazon.com and were called “Plastruct AR-2H Clear Rod, 1/16”” belonging to the brand Plastruct.
This method is fairly similar to the method to create the GFRC fiber prototype. The dimensions of the
prototype will be 8” by 4” by 3” with the translucent elements running from one 8” by 3” face to the one
across. The wooden formwork pieces are cut to the required dimension and then nailed to the base. The
formwork pieces that make up the longer side of the prototype will be drilled with holes at a distance of
2cm and these will hold the Plastruct rods in place.
Once the formwork is put together, the rods will be inserted into holes on one side and then passed
through the other side. They will then be pulled tight from both sides to ensure that they are running
straight across from one end to another.
56

A concrete mixture will be mixed using Quikrete in a proportion of 5 parts of the powder with 1 part of
clean water is made. This is mixed well to not have any lumps in the mixture. The wooden part of the form
is coated with cooking spray to allow easy removal of the prototype from the formwork. the cooking oil
spray used for this is the Kroger Cooking oil which is inexpensive. Two generous coats of this spray are
sprayed on to the formwork.
The cement mixture is then poured into the formwork. The cement is then allowed to set for 2 days, after
which the side pieces of the formwork will be removed, and the pieces is taken apart from the base piece.
At this point the prototype will have the Plastruct rods protruding from either side of the cement faces.
These will be clipped with a nail clipper to be in line with the face of the prototype to have an even surface.
The Plastruct rods will be sanded with a medium grit sandpaper on the face that will be emitting light to
allow light to disperse better.
3.5 Glass Capillary Tubes
Glass capillary tubes are usually used for medical purposes and are made of borosilicate glass. The
capillary tubes used for this prototype were ordered from Amazon.com belonging to the brand Uckoko
and the product was called “Glass Capillary Tubes – 100 Pcs 75 mm Capillary Micro Hematocrit Tubing
Melting Tube Lab Sample Supply”. The length of the tubes is 75mm with an inner diameter of 1.1-1.2mm
and an outer diameter of 1.5-1.6mm.
This method involves the use of glass capillary tubes are the light transmitting element. These will be sewn
to attach to the formwork using a needle and thread. The formwork will be made using foam core to
evaluate the ease with which seeing can be done.
The formwork will be of the dimension measuring 8” by 4” by 3” with the translucent elements running
from one 8” by 3” face to the one across. The pieces of foam core will be cut in the desired sizes and glued
together. The pieces that make up the longer sides of the formwork will have holes made in the using any
sharp, thin, pointed object. This will allow the needle to pass through with ease.
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Once the formwork is put together, a needle of 0.180 inches diameter will be sewn with a thread, passed
through the hole on one side of the formwork, and then put through the hollow center of the capillary
tubes. The needle is then passed through the hole on the other side from the inside to fix the glass capillary
tubes in place. The thread is then cut off and tied to secure the capillary tube. This process is then repeated
multiple times to fill all the holes with capillary tubes.
A cement mixture is then prepared using Quikrete and clean water with the proportion of 5:1. The
formwork is placed on a vibrating table and the concrete mixture is filled into it carefully till it reaches the
top of the formwork. Even though the set time for Quikrete is said to be 20 to 40 minutes, the mixture
still takes a month to reach its maximum compressive strength. However, for this experiment the
prototype will be kept aside for a minimum of 2 days to allow the concrete to harden. The formwork is
taken out after 2 days with care.
3.6 Light transmitting formwork
3.6.1 3D printed formwork - 1
This approach uses translucent PETG to transmit light from one end to another. This would be done by 3d
printing a translucent material in a pattern that is desired that will allow light to pass through. This
material would be Polyethylene terephthalate glycol-modified (PETG) 3D printer filament that is vacuum
sealed with desiccant and has high toughness and little shrinkage. (See figure 67) The filament has a
diameter of 1.75 mm with a recommended print temperature of 230 to 260˚ C and should be 3D printed
at 50 mm/s for best results. To achieve transparency in the X and Y axis, it is recommended that layer
heights should be larger relative to the nozzle size used. (Goldschmidt, B. 2019) Larger and spherical layers
tend to refract less light leading to a more transparent 3D printed part. (Goldschmidt, B. 2019) Generally,
printing at 70–90% of the nozzle diameter results in more transparent prints. (Goldschmidt, B. 2019) Once
the part is printed no post-processing required. (Goldschmidt, B. 2019)
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Figure 67 PETG 3D printer filament (https://www.amazon.com/Gizmo-Dorks-Filament-Printers-
Transparent/)
Material Process:
The form that the PETG will be printed on a bed of thickness 0.2 cm will be 3D printed with long extrusions
with a diameter of 0.2 cm that will be running across the thickness of the panels. (See figure 68) The
geometry will be created using a BIM modeling software of Rhino 7 and this geometry will be input into
the 3D printer as a STL file. (See figure 68)

Figure 68 Step 1: 3D print translucent PETG as the light transmitting element
Casting Process:
A wooden formwork is created using wooden boards and sprayed with a release spray so that the cured
form can be taken out of the wooden formwork with ease. The wooden formwork has markings on the
interior to demarcate the level to which concrete needs to be filled to reach the desired thickness of the
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panel. The translucent form will be inserted into a wooden formwork, with the bed placed in the bottom
of the wooden formwork. (See figure 69)

Figure 69 Step 2: Translucent element inserted in wooden form
The concrete mixture is then poured into the formwork to the level marked on the inside. (See figure 70)

Figure 70 Step 3: Concrete poured in wooden form
After the concrete mixture is poured into the formwork, the panel is then allowed to set for 2 days, and
then taken out of the form as seen in the figure illustrating step 3. The form is then allowed to set for a
further 2 days. The panel that is removed has the 3d printed form extruding from the top of the surface
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and the 3D printed bed at the bottom as seen in the fig illustrating Step 4. The extrusions are then chopped
off to be in level with the surface of the panel using scissors. (See figure 71 and 72)

Figure 71 Step 4: Set component removed from form

Figure 72 Step 5: 3D printed form extruding out is cut
The panel is then flipped over to the side with the 3D printed bed. (See figure 73) This surface is the
polished to remove completely and reveal the concrete surface allow the long extrusions to be seen.

Figure 73 Step 6: Form flipped over
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Figure 74 Step 7: PETG 3d printed bed sanded off to reveal the elements running across the thickness of
the panel
Both the edges are then polished so that the surfaces are smooth thus allowing light to pass through from
one surface to another. (See figure 74)
3.6.2 3D printed formwork - 2
This process involves the 3d printing of the translucent element layer by layer to use the material and the
3D process more efficiently using transparent PETG. Figure 75 illustrates one layer of the 3D printed form
which then printed incrementally and the attached to one another using glue. A transparent framework
is formed. (See figure 76)

Figure 75 Step 1: 3D printed translucent PETG as the light transmitting element layer by layer
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Figure 76 Step 2: Attaching the layers
Wooden formwork is made by nailing wooden pieces to fit dimensions of the panel with a marking on the
inside to mark where concrete needs to be filled. The translucent framework created is then placed is the
wooden mold. (See figure 77)

Figure 77 Step 3: Placing the translucent form in the formwork
Concrete mixture is then poured into the formwork and allowed to set for 2 days. (See figure 78) panel
will then be taken out of the formwork and then allowed to set for longer. (See figure 79)
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Figure 78 Step 4: Pouring concrete in the formwork

Figure 79 Step 5: Placing the translucent form in the formwork
Once the panel is cured, the faces that will transmit light will then be grinded until the parts of the
translucent form running across are revealed, thus allowing light to pass through. (See figure 80)

Figure 80 Step 6: Grinding concrete till reveal the elements running across the thickness of the panel

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3.7 Epoxy resin light transmitting form
The epoxy resin used for this prototype was ordered from Amazon.com from the Janchun Store. The
product is called “160z Crystal Clear Epoxy Resin Kit Casting and Coating for River Table Tops, Art Casting
Resin, Jewelry Projects, DIY, Tumble Crafts, Molds, Art Painting, Easy Mix 1:1 Ratio”. For the silicone mold,
the product was also ordered from amazon from the Smooth-On store and the product is called “Smooth-
On Mold Star 20T Silicone Mold Making Rubber – Trial Unit”.
The experiment with epoxy resin will have 5 main steps: 3D printing the geometry of the desired light
transmitting element network; casting a mold using silicone and the 3d printed network; casting the light
transmitting network in the silicone mold; demolding the network and then casting the network in
concrete.
The geometry of the light transmitting element will be created on a 3d modeling software. (See figure 81)
Once the geometry is created it will be 3d printed using PETG filament with zero fill.

Figure 81 Translucent element to be 3D printed
This geometry will be used to create the silicone mold that will be used to cast translucent epoxy resin. A
wooden formwork will be created with one end that is 16cm and the other is 20 cm. The side that is 16cm
long will match the width of the 3d printed geometry created. Wooden pieces are nailed on a base piece.
Once the wooden form is created, the 3D printed geometry is placed at the bottom of the wooden
formwork. This will create a network on the base of the cast silicone mold. To secure the network to the
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bottom of the wooden formwork, tape is used at every other branch. The network and the wooden form
are coated with oil to ensure easy removal of the silicone mold once it is cast.
To make the mold, instructions on the box of the Mold Star 20T, which is going to be used to make the
mold, are followed strictly. (See figure 82) Mold Star 20T is chosen to make the mold for the resin since it
cures into a soft but strong rubber which is also tear resistance. The mold making kit comes with 2 Parts
that have to be mixed in the ratio 1:1. Half the contents of Part A is poured in a container and then half
the contents of Part B is added to Part A. It is important to remember to keep the flow of both parts
uniform so that the air bubbles entrapped inside are kept at a minimum. The directions on the container
of the kit instruct the mixture to be stirred for 5 minutes while scraping the sides and bottom of the
container so that the mixture is even.

Figure 82 Silicone used for the creation of the mold
The silicone mixture will then be poured in the wooden mold prepared earlier with the oil coating. The
instruction on the kit instructs that the mixture needs to be poured at least ½” over the highest point of
the model surface. This instruction will be followed till the 3D printed network is covered till over ½” inch
of the highest point on the model or till the entire prepared mixture is poured in. The mixture will then
be allowed to cure overnight to make sure the silicone is set properly.
Once allowed to cure overnight, the silicone mold is removed from the wooden box. It should have created
an impression of the 3D printed network on the face of the mold. The silicone mold is then placed in the
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same wooden form that it was cast in, but with the face with the 3D printed network face up. This will
prevent the epoxy resin from spilling out of the sides when poured into it. The mold and the inside of the
wooden box will be coated with oil using a brush to facilitate the removal of the cast resin network. The
silicone mold is then ready to be poured with the epoxy resin mixture to create the translucent element.
A clear epoxy resin is used to create this translucent element (see figure 83). This particular company is
chosen since they claim to create crystal clear resin products that resist yellowing and are self-leveling.
This mixture also has a long work time of 30 to 40 minutes thus making it convenient. The kit contains of
2 parts, part A being the resin and part B being the hardener and the ratio that it is supposed to be mixed
is 1:1. 1/3
rd
of the contents of part A is added to a container and then the same proportion is added. The
mixture will be stirred slowly for 5 to 6 minutes as instructed on the kit.

Figure 83 Epoxy used for the creation of the light transmitting element
The ready epoxy resin mixture will then be poured into ready wooden form with the silicone mold with a
light oil coat. Once the resin mixture fills all the branches of the mold shape created by the 3D printed
network, the mold will be lightly tapped to make sure the resin is leveled in the channels. This is the
allowed to cure in the silicon mold overnight to ensure that the translucent epoxy network is cured
properly. Once allowed to cure, the silicone mold with the resin cured in it will be removed from the
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wooden form. The cured network will be carefully removed from the silicone formwork one branch at a
time.
The same wooden form will be used for casting the epoxy resin network in concrete. A concrete mixture
will be made using Quikcrete and the mixture will be made using 5 parts of Quikcrete and 1 part of clean
water. This will be mixed thoroughly to remove any lumps in the mixture. The Quikrete mixture will be
poured into the wooden form to reach half the level of the form. The resin network will be placed on the
layer of concrete and then another layer of concrete will be poured on top of the resin network. This is
then allowed to set for 2 days for the concrete to cure.
Once cured, the cast concrete will be removed from the wooden box. If the ends of the resin network are
not seen on either side of the cured prototype, the concrete sides will be cured until the ends are revealed.
3.8 Conclusion
The flowability of concrete and the six methods of production discussed in this chapter will be carried out
for the purpose of this research. Some of these methods and materials have been experimented with
earlier. It is not guaranteed that the methods and materials that have not been experimented with yet
will work, however, it will be of value to the scope of translucent concrete.

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Chapter 4
4. Fabrication of prototypes
Chapter 3 discusses the method of flowability of concrete and 6 different methods of production of
translucent concrete. The method of flowability is tested to figure out the optimum mixture of Quikrete
and water that will be required for the 6 different tests of translucent concrete prototypes. This will be
determined by the nature of the translucent elements being embedded in the concrete.
The six different prototypes of translucent concrete, as outlined in the previous chapter, will be using glass
fibers as used in GFRC panels, acrylic fibers, Plastruct rods, glass capillary tubes, 3D printed light
transmitting network and epoxy resin light transmitting network. These methods can be divided into 2
categories based on the type of light transmitting element used in the prototypes – existing translucent
objects and created light transmitting elements. The existing translucent objects comprise of the glass
fibers used in GFRC panels, acrylic fibers, Plastruct rods and glass capillary tubes; whereas the created
light transmitting elements include the 3D printed light transmitting elements and the epoxy resin light
transmitting network. It is important to note these 2 categories since the first – existing translucent
objects will have a certain level of success in transmitting light since their translucency is guaranteed,
however, with the second category it the creation of new translucent elements that may or may not be
successful in light transmission.
It is also important to note that, out of the 6 experiments being carried out in the scope of this thesis,
there are 2 materials that are being used, or are similar to the material being used in the existing
production of light transmitting concrete. Existing production method of translucent concrete involves
the use of acrylic or glass fibers in translucent concrete panels, acrylic fibers being the most common
owing to its low cost. Acrylic fibers are used as one of the materials to experiment with in this research to
understand how the material works in the existing production of translucent concrete panels. Plastruct
rods is the other material that is similar to the existing material of acrylic fibers used in the existing
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production method since they are also made using an acrylic material but only differ in terms of their
diameter or thickness. The purpose of using this material is to understand how the difference in diameter
of the Plastruct rods affects the light transmission through the thickness of the prototypes.
This chapter discusses the various issues, successes, and failure of the (six) different methods of
production of translucent concrete as discussed in the previous chapter.
4.1 Testing Quikrete concrete mix and formability of concrete using a polygonal mold or formwork
Quikrete is the largest manufacturer of packaged concrete and is the most widely available concrete mixes
in the United States. It can be used in structural repairs to surfaces and is easy to mold in the desired
shapes and sizes. This company was chosen since the material is easy to obtain and that it has a short
setting time. The website of Quikrete says that it sets in 20 to 40 minutes with a compressive strength of
6000 psi and this would allow more prototypes to be made testing different methods and materials.
A test was performed to understand the flowability of concrete in a formwork that was created using
foamboard. In this case, the dimensions of the polygonal formwork have been mentioned in the chapter
3 section 3.1. this particular size of each of the polygonal opening is chose to allow better flowability of
the concrete mixture from one to another. A strip of foamcore is cut with the dimension of 4 inches that
would be the thickness of a thin panel. The foam board was cut in a strip and scores were made at the
edges to allow folding of each component. A glue stick was inserted in the hot glue gun and allowed to
heat until the glue reached a semi liquid state allowing it to be used to stick the strip of foam core to the
base.
The base is prepared by using a transparent acrylic sheet glued on to the foam board to prevent the water
from the cement mixture seeping into the base foam board. The acrylic sheet facilitated the removal of
the formwork from the base.
Openings were created in the walls, so that the concrete can cross over from one pocket to another (see
image 84). This would allow the concrete components to behave as a homogenous material and give more
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strength to the concrete structure being formed. The foam board is used as an alternative to the acrylic
formwork that will be used in the prototype. (See figure 84)

Figure 84 Acrylic Formwork Production
The concrete mixture is then produced by mixing 5 parts of Quikrete and 1 part of clean water in a bucket.
This is mixed thoroughly to remove any lumps from the mixture and allow smooth flow of the mixture
into the formwork. The mixing process will be essential when making the prototypes since the lumps could
get stuck in the fibers making the process difficult.
Once the mixture is prepared it is poured into one of the pockets and pouring is continued until the
concrete mixture pours into the other pocket allowing it to reach the top of the formwork. (See figure 85)
However, the concrete is spills from the base from under the formwork to the outside and to the other
pockets. This could be owed to the fact that the formwork had space between the base the formwork.

Figure 85 Pouring Concrete
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From this experiment, it was understood that there the amount of water in concrete can be increased or
decreased as required for the prototype and the kind of flowability required. However, it needs to be
remembered that as the amount of water in the concrete mixture increases the structural strength of the
prototype decreases.
4.2 Prototype 1 – Using fiberglass used in GFRC Panels
The glass fibers used in GFRC panels is called fiberglass and it comes in the form of a yarn. It has high
strength corrosion and high temperature resistance allowing it to be embedded in concrete. Fiberglass is
used as chopped pieces in GFRC panels to provide higher structural strength. Since these fibers are also
made of glass, it is likely that these fibers will allow light to pass through if continuous fibers are allowed
to pass through from one face of the panel to the other.
The fiberglass used in the production of the prototype for this experiment was received from the precast
company Clark Pacific. The company buys the fiberglass yarns to use as chopped pieces in their GFRC
panel production. For this experiment around 70 ft of glass fiber was cut from a yarn of fiberglass and
received from the company. (See figure 86)

Figure 86 Continuous Glass Fibers
The formwork was made using plywood material and the base used was a MDF Board. (See figure 87)
These materials were chosen for the formwork since they are easy to work with in terms of cutting to the
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right size and can be easily put together to form the formwork using carpenter nails. Both plywood and
MDF boards are also inexpensive and if taken apart correctly can be reused for the other prototypes. They
can also be taken apart easily using a hammer and chisel. The pieces are cut with dimensions using a band
saw as mentioned in chapter 3 section 3.2. Nails of 1-inch length were used in a nail gun to put these
pieces together. Firstly, a rough sketch of the desired measurements of the prototype (as mentioned in
section 3.2) were drawn on the base MDF board. The shorter pieces making up the formwork are nail
gunned to the base by holding the base and the pieces in place off a table with added support from the
top. It is imperative to be careful during this step so as to avoid being hurt by the nail gun. The longer
pieces, that are half the height of the total depth of the panel are then nailed to base using the same
technique as the shorter side.

Figure 87 Formwork Materials
Markings are made on either side of the longer side where the nails need to be placed, these are 1 cm
apart from one another. Nails of the height 2 inches were attached on either side of the longer pieces to
wind the glass fibers around them. (See figure 88) This facilitated the process of placing the optical fibers
as compared to the manual placement of the optical fibers individually in molds.
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Figure 88 Formwork
It was equated that one acrylic fiber that is used in the existing manufacture of translucent concrete would
be equivalent to the thickness of 10 loops of the fiberglass. It was decided owing to the filigree nature of
the fiberglass, one single strand of the fiberglass would not allow sufficient light to pass through. Thus,
the idea of looping was tried out in this process. Looping was done in 3 different configurations: 10 Loops,
30 Loops, 50 Loops, as seen in figure. This was done to understand how the looping affects the amount of
light coming through. (See fig 90)
The winding process started with tying the end of the fiberglass to one nail at the side of the panel and
then winding it around the other to be as tight as possible, and then looped 10 times (for the first 5
corresponding nails. (See figure 89) This looping process was iterated for the other two looping
configurations: 30 times (for the second group of 5 corresponding nails) and the 50 times (for the last
group of 5 corresponding nails). (See fig 90)
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Figure 89 Winding method
During the winding process, the fiberglass kept breaking since they can be considered brittle in nature.
This meant that the amount of pressure applied to keep the fibers tight needed to be taken care of. Hot
glue was also used as an added measure at the beginning and end of each looping in every configuration
for two reasons – to keep the fibers from breaking due to pressure as well as keeping the looping or the
multiple fibers in each looping together. This would allow each looping configuration to act as cohesive
group rather than splitting into their individual fibers. With the 10-loop configuration, the hot gluing
method to keep the fibers worked well, however it did not work well for the 30 and the 50 loop
configuration since the number of fibers were too many to stick together efficiently. (See figure 90)

Figure 90 Looping configuration
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Once the looping is done around all the nails, the second layer of the longer formwork is nailed on top of
the fibers for two reasons – to hold the fibers in place as well as meet the total depth of the prototype
required. To provide additional support to the formwork and to avoid spilling of concrete to the outside,
the corners of the formwork were closed using duct tape.
The concrete mixture is prepared by mixing 5 parts of Quikrete and 2 parts of clean water in a bucket. This
is mixed thoroughly to remove any lumps from the mixture and allow smooth flow of the mixture into the
formwork. The mixing process was essential since the lumps could get stuck in the fibers making the
process difficult. It is possible for the concrete to overflow onto the top of the sides of the formwork. (See
figure 91) once the concrete is poured into the formwork, the base is tapped by hand continuously for 5
minutes to remove any air bubbles from the prototype.

Figure 91 Concrete mix poured into formwork
Quikrete instructions say that the concrete can be allowed to set for 2 days, however after two days of
allowing the prototype to be set, the shorted side plywood pieces and the longer top pieces were taken
apart and it was noticed that the prototype was still wet. This meant that the concrete needed more time
to cure and set properly. (See figure 92)
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Figure 92 Formwork partially removed
After allowing the prototype to set for 2 more days, a color change was seen which meant that the protype
was now cured and could be taken apart. A nail clipper was used to cut the fiberglass from the nails from
either side. The nails on either side as then taken out using a hammer and the longer pieces of the
formwork remaining are removed. The prototype is separated from the base MDF piece. (See figure 93)

Figure 93 Concrete block with fibers removed from the formwork
The remaining protrusions of the fiber glass were cut using nail clippers to get as close to the block as
possible. (See figure 94) It can be seen that the face of the prototype that the light transmission will occur
from is not a clean face and this may be due to the two different long pieces that were used to hold the
fiberglass in place. (See figure 94)
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Figure 94 Finished block
During the process of taking the prototype apart from the formwork, certain edges and faces of the
concrete were chipped off, however, this does not affect the quality of light transmission passing across
the prototype. (See figure 95)

Figure 95 Finished block close-up
4.3 Prototype 2 – Using Acrylic Fibers
Acrylic fibers are used in the commercial production of translucent concrete production with only one
fiber running across. This experiment was done to understand how looping of these optical fibers in
groups will impact the light transmission from one end to another. Another aspect of the light
transmission through optical fibers was experimented. Usually, the optical fibers run straight across from
one end to another. This experiment also entails optical fibers running diagonally from one nail to another
that is not running straight across from the start nail.
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The acrylic fibers used for this experiment are of the diameter of 0.25 mm with a fiber cable operation
temperature of -58 to 167 degree F with a lifetime of more than 20 years. The material is also good at
heat insulation. The material is also flexible to be wound around nails. These acrylic fibers were ordered
from Amazon.com from the brand Azimom and are called “PMMA Plastic End Glow Cuttable Fiber Optic
Cable roll for Star Sky Ceiling – All kind LED Light Engine Driver Source”. (See figure 96) The pictures of the
fiber on the website showed led lights being transferred from one end and claimed to be used for starry
skyed ceilings as in certain high-end cars. They costed $11.88 for a 328 ft of the fiber.

Figure 96 Plastic optic fibers (from Amazon; Company Azimom)
The wooden formwork is prepared by sawing pieces to the desired dimensions. These pieces were then
nailed to the base using a nail gun, by holding the pieces firmly on the base off a table. This will allow the
pieces to be nailed from below. The acrylic fibers are wound around nails that are nailed along the long
side of the formwork. The nails are placed 1 cm off from the wooden form.
The method of making the formwork as well as its dimensions are fairly similar to the process of the
prototype using glass fibers. The formwork was made using plywood and these materials were chosen for
the formwork since they are easy to work. Both plywood and MDF boards are also inexpensive and if
taken apart correctly can be reused. They can also be taken apart easily using a hammer and chisel. The
pieces are cut with dimensions using a band saw as mentioned in chapter 3 section 3.3. Nails of 1-inch
length were used in a nail gun to put these pieces together. Firstly, a rough sketch of the desired
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measurements of the prototype (as mentioned in section 3.3) were drawn on the base MDF board. The
shorter pieces making up the formwork are nail gunned to the base by holding the base and the pieces in
place off a table with added support from the top. It is imperative to be careful during this step so as to
avoid being hurt by the nail gun. The longer pieces, that are half the height of the total depth of the panel
are then nailed to base using the same technique as the shorter side.
To facilitate the placement of the nails, markings are made on either side of the longer side, and they are
1 cm apart from one another and 1cm away from the outside edge of the formwork. Nails of the height 2
inches were attached on either side of the longer pieces to wind the glass fibers around them. (See figure
97) This facilitated the process of placing the optical fibers as compared to the manual placement of the
optical fibers individually in molds. The nails are also an easy material to be used to wind the flexible fibers
around.

Figure 97 Wooden Formwork with nails on either side
The method to wind optical fibers starts with the optical fiber being double tied on one nail, winding it
over the nail that runs directly across from the first nail tightly and then tying it. To secure the nail, the
optical fiber is also hot glued to both the nails that it has been tied to or been looped over. This process is
iterated for all the nails keeping in mind the looping configurations that have been decided.
Looping is done in the following system: 1
st
3 nails: 1 loop; next 3 nails: 2 loops; next 2 nails: 5 loops and
the next two: 8 loops. The rest of the next 4 nails have lopping that go diagonally across. The 4 nails are
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labeled: A, B, C, D on one side and following that, the nails that run straight across are labeled the same
respectively. (See table 6) One side is labeled 1 and the other is labeled 2. (See fig 98)
Table 7 Diagonal looping configuration
Side 1 Side 2
A C
B D
C B
D A

Figure 98 Looping configurations

Figure 99 Optical fiber looping configuration
The looping process of optical fibers was more convenient and easier to carry than the GFRC fibers since
they are not brittle in nature. This can be owed to the material, which is acrylic, of the fibers. They did not
break during looping as the GFRC fibers did. The concrete mixture is prepared by mixing 5 parts of Quikrete
and 1 part of clean water in a bucket. The concrete mixture for this prototype had lesser water since the
concrete mixture prepared for 2 reasons - the prototype using glass fibers had taken longer to dry and the
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acrylic fibers being stronger could take the load of a thicker concrete mixture. The mixture is similarly
mixed thoroughly to remove any lumps from the mixture and allow smooth flow of the mixture into the
formwork. The mixing process was essential since the lumps could get stuck in the fibers making the
process difficult. It is possible for the concrete to overflow onto the top of the sides of the formwork. (See
figure 100) The concrete mixture is thicker than it was for Prototype 1.

Figure 100 Pouring of cement mixture
Once the concrete is poured into the formwork, the base is tapped by hand continuously for 5 minutes to
remove any air bubbles from the prototype. (See figure 101)

Figure 101 Prototype with cement mixture
After allowing the prototype to set for 2 more days, a color change was seen which meant that the protype
was now partially cured and could be taken apart. A nail clipper was used to cut the fiberglass from the
nails from either side. The nails on either side as then taken out using a hammer and the longer pieces of
the formwork remaining are removed. The prototype is separated from the base plywood piece. The
remaining protrusions of the fiber glass were cut using nail clippers to get as close to the block as possible.
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(See figure 102) It can be seen that the face of the prototype that the light transmission will occur from is
not a clean face and this can be owed to the two different long pieces that were used to hold the fiberglass
in place.

Figure 102 Finished prototype
4.4 Prototype 3 – Using Plastruct rods
Acrylic as a material is known to be good for light transmission and this experiment was done to
understand the performance of a thicker acrylic material in light transmission. The Plastruct rods used for
the experiment are of the diameter of 1/16” and is made of clear acrylic material. (See figure 103)

Figure 103 Plastruct rods
(from Amazon.com; brand: Plastruct)
A wooden formwork is made that is 3” deep, 4” wide and 8 ½” long as mentioned in Chapter 3 section
3.4. The formwork was made using plywood material and these materials, similar to prototypes 1, 2 and
3, were chosen for the formwork since they are easy to work with in terms of cutting to the right size and
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can be easily put together to form the formwork using carpenter nails. They can also be taken apart easily
using a hammer and chisel. The pieces are cut with dimensions using a band saw as mentioned in chapter
3 section 3.2. The long side that will have the light transmitting elements running across have holes to
hold the acrylic rods. The holes that are 2cm apart are made using a drill press with a drill bit of the
dimension 1/16”.
Nails of 1-inch length were used in a nail gun to put these pieces together. Firstly, a rough sketch of the
desired measurements of the prototype (as mentioned in section 3.4) were drawn on the base MDF board.
The shorter pieces making up the formwork are nail gunned to the base by holding the base and the pieces
in place off a table with added support from the top. It is imperative to be careful during this step to avoid
being hurt by the nail gun. The longer pieces are then nailed to base using the same technique as the
shorter side.
One rod is then inserted from the outside in the hole and then pulled through to be inserted through the
inside of the corresponding hole on the other end. The rod is pushed through the hole so that it comes
out of the other end. The Plastruct rods are then pulled from both ends so that the rods are parallel to
the base. This method is then iterated until all the holes are filled with the rods. (See figure 104)

Figure 104 Material in formwork
The corners of the formwork need to be secured to avoid any spilling of the concrete and this is done by
taping the edges using duct tape. The cement mixture is then prepared using 5 parts of Quikcrete and 1
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part of clean water and mixed according to the instructions on the container to remove any lumps from
the mixture. The mixture is then poured into the mold and allowed to set for 2 days. (See figure 105)

Figure 105 Concrete poured in the form work
Once dried, the prototype is ready to be removed from the formwork. The duct tape is cut off the edges
and the shorter sides of the formwork are taken out first since they do not have translucent element
running through them. The longer pieces need to be taken out carefully since the Plastruct rods can break
while doing so. To minimize the possibility of the Plastruct rods breaking, the rods are cut using a nail
clipper as close to the outer face of the formwork. The nails are removed from under the base piece using
a hammer and the wooden pieces are then slowly pulled apart from the prototype. The remaining
protrusions of the Plastruct rods were cut using nail clippers to get as close to the block as possible. (See
figure 106) It can be seen that the face of the prototype that the light transmission will occur from is not
a clean face and this can be owed to the two different long pieces that were used to hold the fiberglass in
place. It is a widely known fact that sanding or roughing the edges of acrylic material allows light to
disperse better than leaving them the way they are. This is done to the first fiber on the end that light will
come out from using a sandpaper of high grit number of 180 which has a finer abrasion quality to create
a smooth surface at the edge of the Plastruct rods.
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Figure 106 Finished prototype
4.5 Prototype 4 – Using Glass Capillary Tubes
These capillary tubes are usually used for medical purposes and are made of borosilicate glass. The
capillary tubes used for this prototype were ordered from Amazon.com belonging to the brand Uckoko
and the product was called “Glass Capillary Tubes – 100 Pcs 75 mm Capillary Micro Hematocrit Tubing
Melting Tube Lab Sample Supply”. (See figure 107) The length of the tubes is 75mm with an inner diameter
of 1.1-1.2mm and an outer diameter of 1.5-1.6mm.

Figure 107 Capillary Tubes
(From Amazon.com, Brand: Uckoko)
The formwork is made using foam core since the material is easy to pierce. The width of the prototype
across which light will be transmitted needs to be the length of the material, which is 75mm or 7cm. The
pieces of the formwork are cut using a utility knife and a cutting mat. The longer pieces of the formwork
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are pierced with holes using nails at a distance of 2cms in between each of them. The pieces making up
the formwork are then hot glued to a base.
The method of production of prototype using glass capillary tubes involves the use of thread a needle.
The first step is to sew the thread in the needle and knot the ends so that the thread does not go through
one end of the capillary tubes and come out of the other side. The needle is sewn through the first hole
till the thread is completely through the hole and is blocked by the knot on the thread. Once the needle
is on the inside, it is sewn through the capillary tube till the end of the tube touches the side through
which it was sewn first. (See figure 108) The needle is then sewn through the corresponding hole on the
other end on the formwork until the tube is held tightly between the holes on either side. The needle is
then inserted into the hole next the one that it came out from, and the entire process of the needle being
sewn through the tube and then inserted through the corresponding hole on the other side. This process
is iterated until all the corresponding are holding up the capillary tubes.

Figure 108 Weaving of capillary tubes through formwork
Once all the capillary tubes are being held in place by the thread passing through the holes, the formwork
is ready to be casted with concrete. A similar mixture of concrete as the previous experiments is made
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using 5 parts of Quikrete and 1 part of clean water. The mixture is then poured into the formwork and
then allowed to cure for 2 days. The mixture needs to be poured carefully so that the tubes do not break
due to the weight of the concrete mixture.
After 2 days of curing, the thread between the 2 holes on the outside of the formwork is cut off between
all the connecting capillary tubes and the prototype is then taken out of the formwork. (See figure 109)

Figure 109 Finished prototype
4.6 Prototype 5 - 3D printed Light Transmitting network
The prototype production involves the creation of new translucent objects for the purpose of production
of translucent concrete. Instead of using existing translucent materials, new translucent elements can be
made by the method of 3D printing and using translucent filament. For the production of the translucent
elements, a transparent filament was used. It was ordered from Amazon.com and belonged to the
Polymaker Store. The product is named “Polymaker PETG Filament 1.75mm, transparent PETG, 1kg Strong
PETG Filament Cardboard Spool – PolyLite PETG 3D Printer Filament, Print with Most 3D Printers Using 3D
filament” and costed $21.99 per spool. PETG is the material chosen since it has good mechanical and
thermal properties.
For this prototype, 2 different 3D printed geometries are explored – 5A and 5B using a 3D modeling
software of Rhino7. These geometries are 3D printed using the Raise3D Pro2 3D printer. While printing,
the settings used are - Nozzle temperature: 235 degrees Celsius, Bed temperature: 70 degrees Celsius
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with a speed of 45 mm/s. the geometry is printed with 0% fill and single layer with a resolution height of
0.22mm in order to have the 3D printed network be translucent.
4.6.1 Prototype 5A Production
The geometry of the 3D printed network is generated on Rhino 7 using a network of lines and a circle of
the diameter of 2mm that is extruded along the line network. The network is of dimensions 16cm by
16cm. A wooden formwork of those dimensions is also created to hold the 3d printed network perfectly.
The first prototype has extrusions that can allow the layers to be stacked on one on top the other. (Seen
figure 110)

Figure 110 Geometry of prototype 5A
The 3D printed transparent geometry of one network is printed in layers and takes around 1.5 hours to
be printed. The whole network was also more fragile than expected and on branch of the network broke
as soon as the geometry was printed. (See figure 111) Since the geometry is printed in layers and is not
extruded as one single geometry, the network did not get printed as translucent as desired (See figure
112).
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Figure 111 3D printed light transmitting formwork

Figure 112 Close up of 3D printed light transmitting formwork
Another drawback of the geometry of this network is that after embedded in concrete, a large layer
from both sides of the finished prototype would have to be removed to reveal the elements that would
be running across from one face of the prototype that would pass light into it as well as where the light
would come out from. With these shortcomings of this prototype, it was decided to experiment with
more geometries to be 3D printed to get the desired form of network that would be sturdier and more
translucent.
4.6.2 Prototype 5B Production
Similar method of production of geometry as prototype 5A for 3D printing was adopted for prototype 5B.
The geometry of the 3D printed formwork is generated on Rhino 7 using a network of lines and a circle of
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the diameter of 2mm that is extruded along the line network. The network is of total dimensions 16cm by
16cm. (Seen figure 113)

Figure 113 Geometry of prototype 5B
As opposed to the previous geometry that had vertical elements that would allow each layer to be stacked
on one on top of the other, this prototype does not have any vertical elements. This prototype is
envisioned similar to the existing knit fabric of acrylic fibers used in the existing production of light
transmitting concrete.
Similar 3D printing settings are used for this prototype using the translucent PLA filament ordered from
Amazon.com using the Raise3D Pro2 3D printer. While printing, the settings used are the same as well -
Nozzle temperature: 235 degrees Celsius, Bed temperature: 70 degrees Celsius with a speed of 45 mm/s.
the geometry is printed with 0% fill and single layer with a resolution height of 0.22mm in order to have
the 3D printed network be translucent.
Once the network was 3D printed, the same observations were made with this prototype as prototype
5A. The 3D printed network can be seen to be almost opaque with very little translucency. (See figure
114) This happens due to the inherent layers produced during the 3D printing process causing the light
rays entering to immediately scatters. This 3D printed geometry is not a monolithic structure and has an
intricate microstructure owing to the layered 3D printing. An element in the middle has been added to
keep the branches together and the vertical elements have been eliminated.
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Figure 114 3D printed light transmitting formwork
Even with the vertical elements being eliminated, a big drawback of this prototype still remains its light
transmission quality. The 2 branches holding the ends of the branches that would have played the role of
transmitting light across the prototype would still have to be sanded down once embedded in the
concrete to reveal the branches running across the width of the prototype. Thus, this prototype can also
be considered as a failure in terms of creating a light transmitting 3D element.
4.6.2 Prototype 5C Production
A step forward from prototype 5B has been taken to design a better network. This prototype is made such
that the vertical elements from prototype 5A and the horizontal elements connecting the light
transmitting elements are the ends have been eliminated. There is once branch in the middle of the light
transmitting element that connect each other to facilitate their placement in the formwork. (See figure
115)
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Figure 115 Geometry of prototype 5C
Similar 3D printing settings are used for this prototype using the translucent PLA filament ordered from
Amazon.com using the Raise3D Pro2 3D printer. While printing, the settings used are the same as well -
Nozzle temperature: 235 degrees Celsius, Bed temperature: 70 degrees Celsius with a speed of 45 mm/s.
the geometry is printed with 0% fill and single layer with a resolution height of 0.22mm in order to have
the 3D printed network be translucent.
This 3D printing prototype network is the most translucent out of the 3 prototypes that have been
tested. (See figure 116)

Figure 116 3D printed light transmitting formwork
This prototype, however, still does not have the desired translucency that would be needed for light to
pass through once embedded in concrete. (See figure 117 and 118) As with the other 3D printed network
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prototypes, the process of 3D printing which happens in layer to form each branch proves to be a
drawback in terms of light transmission. However, since the geometry for Prototype 5C was most
promising, it could be used to create a light transmitting network using epoxy resin in the next prototype.

Figure 117 3D printed light transmitting formwork

Figure 118 3D printed light transmitting formwork
4.7 Prototype 6 - Epoxy Resin light transmitting network
In the process of production on Prototype 5 using 3D printed light transmitting formwork, it was realized
that the 3D printing the light transmitting element did not have an outcome of translucency. Thus, it was
decided that the geometry of the 3D printed light transmitting formwork 3 would be used to create an
epoxy resin light transmitting network. The epoxy resin used for this prototype was ordered from
Amazon.com from the Janchun Store. The product is called “160z Crystal Clear Epoxy Resin Kit Casting and
Coating for River Table Tops, Art Casting Resin, Jewelry Projects, DIY, Tumble Crafts, Molds, Art Painting,
Easy Mix 1:1 Ratio” and costed $17.99 for the 16oz bottle. For the silicone mold, the product was also
ordered from amazon from the Smooth-On store and the product is called “Smooth-On Mold Star 20T
Silicone Mold Making Rubber – Trial Unit” costing $35.99 for the pack.
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The method of production of this prototype involves 5 main steps: 3D printing the geometry of the desired
light transmitting element network; casting a mold using silicone and the 3d printed network; casting the
light transmitting network in the silicone mold; demolding the network and then casting the network in
concrete.
The geometry of the 3D printed formwork is generated on Rhino 7 using a network of lines and a circle of
the diameter of 2mm that is extruded along the line network. The total dimension of the network is 16cm
by 16cm. The geometry is 3D printed using the Raise3D Pro2 3D printer. While printing, the settings used
are - Nozzle temperature: 235 degrees Celsius, Bed temperature: 70 degrees Celsius with a speed of 45
mm/s. The geometry is printed with 0% fill and single layer with a resolution height of 0.22mm in order
to have the 3D printed network be translucent. (See figure 114)

Figure 119 3D printed network
A wooden formwork of those dimensions is also created to hold the 3d printed network perfectly. The
formwork is prepared by sawing pieces to the desired dimensions. These pieces were then nailed to the
base using a nail gun, by holding the pieces firmly on the base off a table. It is imperative to be careful
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while carrying out this step to avoid any mishaps. This will allow the pieces to be nailed from below. (See
figure 120)

Figure 120 Wooden Form
Once the wooden formwork is made, it is observed that there were some openings between the adjacent
pieces. To avoid the concrete from spilling out of the sides, the pieces are held together more tightly using
duct tape. (See figure 121)

Figure 121 Edge protection
The 3D printed network is then placed in the wooden box to make sure of its placement before it is
attached to the base. It was noticed that the network was not flat on the wooden base of the formwork.
(See figure 122)
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Figure 122 Placing the 3D printed network in the wooden form
Earlier, it was planned to have the network stuck to the base using glue, however, glue would not have
been a good medium to stick the PLA 3D printed network to wood. Therefore, it was expected that duct
tape will work better. All the ends and 2 parts of the mid connecting branch of the network are taped
down to the wooden base. (See figure 123)

Figure 123 Placement of 3D printed geometry
The wooden formwork along with the 3D printed network are then coated with oil using a small piece of
cotton. Two spoons of regular vegetable oil are taken out in a bowl, a cotton pad is dipped in the oil and
the formwork is coated. (See figure 124) This will enable the silicone mold to be taken out of the mold
easily.
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Figure 124 Applying a light coat of oil
The next step is to make the silicone mold using the Smooth On kit. The silicone mixture for the mold was
made pouring half the bottle of part A and part B in a glass container and mixed well. A table knife was
used to mix the mixture rigorously since the knife has edges that can facilitate the scraping of the mixture
from the sides of the container. The mixture is mixed well for 4 minutes, and this was done slowly and
carefully to avoid any air bubbles. (See figure 125)

Figure 125 Silicone mold mixture
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The silicone mixture was then poured at an even pace to avoid any air bubbles, into the wooden formwork
that has a light coating of oil, and this was allowed to set in the formwork for over 12 hours. (See figure
126)

Figure 126 Pouring the silicone mixture in the mold
The next day, the silicone mold was removed from the wooden formwork. The first observation was that
the 3D printed formwork did not stay at the base of the wooden formwork, which means that the 3D
printed network was floating in the silicone and that the tape did not successfully keep the 3D printed
network stuck to the base. The tapes hold the network was also seen embedded in the silicone mold. (See
figure 126) It can be seen that some branches of the network have successfully stayed at the base of the
wooden formwork whereas some had disconnected from the base allowing silicone to fill underneath.
(See figure 127)

Figure 127 Silicone mold with the 3D printed formwork
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Figure 128 End conditions of silicone mold
The removal of the 3D printed network from the silicone was not as perfect and clean as expected. The
expectation was that the silicone mold would have the impression of the 3D printed network as channels
or canals on the face of the mold, however since the 3D printed network was lifted from the base, the
channels were not formed properly. The portion of the silicone mold covering the 3D printed network had
to be cut using an xacto knife to remove the 3D printed network from the mold.
The next step was to create the epoxy resin mixture to make the epoxy resin translucent light transmitting
network. The epoxy resin kit from the Janchun Store from Amazon.com was used. The epoxy resin was
mixture was created by mixing 1/3rd of the contents of the part A and B bottles in a glass cup. The mixture
was mixed for 6 minutes, as instructed, using a steel knife to allow for scraping of the mixture from the
sides. (See figure 129) It was noticed that small bubbles were formed in the mixture.

Figure 129 Epoxy Resin mixture
The silicone mold was placed in the wooden formwork with face with the 3D printed network impression
on top. A silicone mold was lightly coated with oil to facilitate the removal of the resin network once
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hardened. The epoxy mixture was then poured into the silicone mold with a steady and slow flow. (See
figure 130) During the pour, it was observed that the resin mixture was not getting into all the channels
properly, thus, the knife was used to smear the liquid into the channels. It was also observed that air
bubbles were forming and to remove the bubble, the knife was used to try to put more resin into the
channels that have bubbles. (See figure 131)

Figure 130 Pouring the epoxy resin into silicone mold

Figure 131 Epoxy Resin curing the silicone mold
The epoxy resin hardened network is removed from the silicone mold by taking apart from the silicone
mold one branch at time. (See figure 132)

Figure 132 Epoxy Resin formwork
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Figure 133 Epoxy Resin formwork

Figure 134 Epoxy Resin formwork

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Chapter 5
5. Results
5.1 Testing Quikrete concrete mix and formability of Concrete using a polygonal mold or formwork
Quikcrete was a good choice in concrete mixture owing to its fast-setting time and easy workability. Since
Quikcrete is mimics large scale use of concrete well, it is easy to understand its workability at larger scales
with the light transmitting elements embedded in it.
The assumption made earlier in the thesis that almost every prototype would require a different Quikcrete
mixture in terms of thickness was carried out during the production of each prototype. This allowed
optimum pouring into each prototype.
From this experiment, it was understood that there the amount of water in concrete can be increased or
decreased as required for the prototype and the kind of flowability required. However, it needs to be
remembered that as the amount of water in the concrete mixture increases the structural strength of the
prototype decreases making the concrete in the prototype drier.

Figure 135 Pouring Concrete
5.2 Prototype 1 – Using glass fibers used in GFRC Panels
The glass fibers used in GFRC panels is called fiberglass and it comes in the form of a yarn. It has high
strength is corrosion and high temperature resistance allowing it to be embedded in concrete. Fiberglass
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is used as chopped pieces in GFRC panels to provide higher structural strength. Since these fibers are also
made of glass, it is likely that these fibers will allow light to pass through if continuous fibers are allowed
to pass through from one face of the panel to the other.
The main objective of this experiment was to prove that optical fibers used in glass reinforced concrete
can transmit light. As the prototype was prepared, it was placed in a dark room and a light was placed at
one end of the prototype. The first looping configuration of 10 fibers, can be seen to transmit light through
to the other end. (See figure 136) However, the looping does not stay well together; in the first image it
can be seen that the 10 fibers form a rectangular bunch and the other two have taken a rectangular bunch.
One of the 10 looping configurations was sanded down to understand whether roughing the edges would
help light passing through disperse better. The 10 loops took around 20 minutes per loop. It was difficult
to carry out the looping since the glass fibers are brittle in nature and would break easily if too much
pressure was applied to it. Therefore, careful handling of the fibers while looping was essential. It is a
known fact that roughing the edge of acrylic materials allows good dispersion of light through the roughed
ends. Owing to the thin diameter of the fibers, the sanding, however, did not work well for the fibers. The
concrete around the fiber looping that was sanded out caused the concrete to granulate and settle
between the fibers in the looping configuration, thus causing light dispersion to reduce.(See figure 137)

Figure 136 Light Transmission through 10 loop configuration
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Figure 137 Sanded down fibers in 10 loops
The 30-loop configuration took around 40 minutes per loop. Similar processes and observations were
made during the process of making of the prototype. The fibers in the looping did not stay well together,
however the looping configuration did allow light to pass from one end to another. (See figure 138) One
of the looping bunches was sanded down to see if the result was the same as the 10-looping configuration.
It was observed that the sanding of the edges, cause concrete particles from around the looping to settle
in between the fibers and reduce the intensity of light passing through. (See figure 139)

Figure 138 Light Transmission through 30 loop configurations

Figure 139 Sanded down fibers in 30 loops
The 50-loop configuration took around 50 minutes per loop. Similar processes and observations were
made during the process of making of the prototype. The fibers did not stay well together the most out
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of all the looping configuration. (See figure 140) One of the 50 looping configurations were sanded down,
and the result was the same as the other configurations. The particles from the concrete settled between
the fibers and reduced the amount of light passing through. (See figure 141)

Figure 140 Light Transmission through 50 loop configuration

Figure 141 Sanded down fibers in 50 loops
Through the images, it is clearly evident that the configuration with 10 loops performs the best in terms
of the fibers staying together. As the number of fibers in a looping configuration increase the amount of
light passing through will increase, however, this does not mean that the looping configurations with
larger number of fibers is optimum. The amount of time taken for the looping as well as the fibers in the
looping not staying together are major drawbacks in the 30 and 50 loops configuration. However, the
looping configuration of 10 fibers stay well together and are integrated into the concrete the best from
the 3 different configurations.
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5.3 Prototype 2 – Using Acrylic Fibers
Acrylic fibers already in use in the commercial translucent concrete elements. This experiment was done
to understand the materiality of the material and how looping will affect the light passing through. From
the figure 139 it can be observed that as the looping increases the amount of light also increases. When
viewed closely the loops that have multiple fibers, the multiple fibers can be seen. (See figure 139)
Once the prototype was prepared, the prototype was placed in a dark closet and a flashlight was used to
pass light through one end of the fibers. For documentation, a phone is placed on a tripod so that the
camera is as stable as possible while taking picture. The light passing through is then documented by
turning down the exposure on the camera and clicking the picture. (See figure 142 and 143)

Figure 142 Light transmission through the block

Figure 143 Looping of fibers evident when seen closely
The loops of 3, 5 and 8 acrylic fibers perform well to transmit light from one end to another. It can be said
that the amount of light transmitted through 3 fibers is equivalent to 3 times the amount of light
transmitted through 1 fiber. This can also be said about the 5 and 8 looping configurations. However, the
looping does not stay together, it is difficult to make sure that the bunch of the fibers in 1 loop do not
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flatten. It can be concluded that this method works well with both, single fibers as well as looping of
multiple fibers in one bunch. The single fibers running straight across from one end to the other as well
as the fibers running diagonally work well to transmit light from one end to another.
5.4 Prototype 3 – Using Plastruct rods
Plastruct rods are fairly similar to the acrylic fibers used in large scale production of translucent concrete.
This experiment was done to understand the behavior of this material when embedded in concrete and
the effect that the sanding down the edges has on the quality of light passing through.
Once the prototype was prepared, the prototype was placed in a dark closet and a flashlight was used to
pass light through one end of the fibers. For documentation, a phone is placed on a tripod so that the
camera is as stable as possible while taking picture. The light passing through is then documented by
turning down the exposure on the camera and clicking the picture. (See figure 144)

Figure 144 Light transmission through the block
It can be seen that once the acrylic rods are roughed up using a sandpaper, disperse light more than the
acrylic rods that are not sanded down. (See figure 145)
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Figure 145 Light transmission through the block after sanding the rods

5.5 Prototype 4 – Using Glass Capillary Tubes
Capillary tubes are made using glass and glass is known to be a good conductor of light meaning that it
can transmit light well. From first observations, it can be seen that some capillary tubes do not pass light
as well as others and this can be attributed to the fact that some of them broke with the weight of the
concrete mixture when poured into the formwork. (See figure 147)
The light is passed through the tube itself and not into through the empty space of the tube. (See figure
146) With the use of capillary tubes in translucent concrete, it does not seem like a viable option owing
to the breaking of the tubes due to the weight on concrete. The open nature of the tube also prevents the
material from being used in an external application since that would allow air and water penetration into
the interiors.

Figure 146 Light transmission through the block
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Figure 147 Differential light transmission due to capillary breaking

Figure 148 Light transmission through the block
5.6 Prototype 5 - 3D printed Light Transmitting network
The light transmitting network was created using a transparent PLA 3D printing filament and was used to
print the light transmitting formwork.
With prototype 5A, the 3D printed transparent geometry is printed in layers and is not extruded as one
single geometry, the network did not get printed as translucent as desired. The vertical elements 3D
printed made the geometry less sturdy and harder to work with. The whole network was also more fragile
than expected causing the geometry to break after being 3D printed. (See figure 149)
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Figure 149 3D printed light transmitting formwork – Prototype 5A
Another drawback of the geometry of this network is that after embedded in concrete, a large layer from
both sides of the finished prototype would have to be removed to reveal the elements that would be
running across from one face of the prototype that would pass light into it as well as where the light would
come out from. This process would be extremely tedious and hard to accomplish. With these
shortcomings of this prototype, it was decided to experiment with more geometries to be 3D printed to
get the desired sturdiness and translucency.
With prototype 5B, the geometry was also not as translucent as required. The 2 branches holding the ends
of the branches that would have played the role of transmitting light across the prototype would still have
to be sanded down once embedded in the concrete to reveal the branches running across the width of
the prototype. (See figure 150) Thus, this prototype can also be considered as a failure in terms of creating
a light transmitting 3D element.
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Figure 150 3D printed light transmitting formwork – Prototype 5B
Prototype 5C can be seen as the most translucent of the 3D printed networks in the experiment. As an
evolution from the previous geometries, the vertical elements as well as the horizontal elements
connecting the light transmitting elements are the ends have been eliminated. (See figure 151) There is
once branch in the middle of the light transmitting element that connect each other to facilitate their
placement in the formwork.

Figure 151 3D printed light transmitting formwork
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This prototype, however, still does not have the desired translucency that would be needed for light to
pass through once embedded in concrete. As with the other 3D printed network prototypes, the process
of 3D printing which happens in layer to form each branch proves to be a drawback in terms of light
transmission. However, since the geometry for Prototype 5C was most promising, and was used in the
production of the next prototype.
5.7 Prototype 6 - Epoxy Resin light transmitting network
The prototype has 5 main steps: 3D printing the geometry of the desired light transmitting element
network; casting a mold using silicone and the 3d printed network; casting the light transmitting network
in the silicone mold; demolding the network and then casting the network in concrete.
During the process of 3D printing, since the geometry gets 3D printed in layers, the 3D printed network
has a texture of those layers on its surface. Since this network is used to form the silicone mold that the
epoxy resin will be cast in, the epoxy resin light network will have the texture on its surface as well. this
may hinder the light transmission process.
While making the silicone mold the 3D printed network did not stay attached to the base of the wooden
formwork and did not create the desired perfect silicone mold and this was the first failure in the
experiment.
However, the epoxy resin was still cast in the imperfect silicone mold causing the epoxy resin network
created to not have smooth edges and clean ends. (See figure 152) Certain branches also did not have a
clear a geometry running across. This failure in the creature of a clean translucent network did not allow
for the network to be tested out embedded in concrete. (See figure 153)

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Figure 152 Epoxy resin network

Figure 153 Epoxy resin network edges
It can be said that if worked with further to perfect the creation of the silicone mold, a cleaned epoxy
resin network could be created allowing a successful light transmitting network to be created. However,
a major drawback of the method of production of this prototype is that it involves many steps allowing
room for failure.

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Chapter 6
6. Discussion and Conclusion
Chapter 6.1 Discussion
The exploration of materials for the purpose of this research realized the translucency of the materials
as well as to understand how light is transmitted through the existing materials in use of production of
translucent concrete panels.
The first material experimented with was fibers used in glass reinforced concrete. This material has not
been used in the production of translucent concrete before. Owing to the filigree nature of the material,
the fibers were looped in 3 configurations of 10, 30 and 50. As the lopping increased it was noticed that
the amount of light increased, however with looping configuration of 30 and 50, the loops did not stay
well together. This means that even though the material works well to transmit light, a better way of
looping method needs to be explored more.
Plastruct rods and acrylic fibers are materials similar to the materials being used in existing methods of
production of translucent concrete. However, since only the manual method of placement of this material
was experimented with, the existing production method of weaving using better technology needs to be
experimented with more.
Capillary tubes made of glass that are ordinarily used for medical purposes, were experimented with next.
The method used to place this in the formwork was that of putting a needle through the tubes and then
weaving them through holes in a formwork. With this material, the process was tedious as well as the
capillary tubes broke with the weight of the concrete mixture being poured in it. Thus, it can be said that
the further experimentation of this material would not be suggested.
The next method explored was that of 3D printing transparent PLA printed. This process involved less
manual labor however takes more time and can be more expensive. Once the transparent framework was
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3D printed, it was realized that since 3D printing happens in layers, this does not allow light to be
transmitted through the framework.
The next material explored was using epoxy resin and this could be considered as a step forward from the
previous method of 3D printing the translucent framework. The 3D printed framework was used to create
a silicone mold that could be used to cast the transparent epoxy material. However, the method using
this material required many steps making it lengthy. Also, the silicone mold to cast the epoxy resin did not
come out as clean as expected. Thus, it can be said that even though this experiment failed to create a
network for the transmitting light the first time, once the method is explored and experimented more can
become a successful method in producing light transmitting concrete.
Table 8 Results
Prototype Light transmission Feasibility
Fiberglass used in GFRC Panels  Can be alternative material in existing
production material
Acrylic Fibers  Already in use
Can be looped in multiple methods
Plastruct rods  Placement of material very tedious
Glass Capillary Tubes  Not feasible since material is delicate and
placement method is very tedious
3D printed Light Transmitting
network
 Has potential to work
Different 3D printing material, 3D printers
and nozzle sizes need to be experimented
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Epoxy Resin light transmitting
network
 Has potential but has many steps that would
mean more room for error
More streamlined process can be successful
The documentation of the amount of light passing through the light elements was done using a phone
camera in manual mode to control the settings of the camera and using a flashlight as the light source.
This process needs to be done using a sensitive light meter and a larger light source to imitate the amount
of light that would be incident on a panel by the sun rays. The light meter would also allow the amount of
light coming out of the other end of the prototype.
Chapter 6.2 Future work
Chapter 6.2.1 Short term
The thesis experiments the workability of Quikrete for the purpose of creating light transmitting concrete
as well as 6 different processes of production of translucent concrete. The use of Quikrete was convenient
owing to its easy workability and short curing time. This allowed for experimentation with multiple
translucent materials, however Quikrete cannot be used in the large-scale production of the prototypes
experimented. The next step would be to experiment with different ratios of cement water and aggregate
to find the optimum mixture to be poured into the formwork with fibers and 3D printed translucent
elements.
Prototype 1 using fiberglass used in GFRC panels had promising results in terms of light transmission,
however the process of winding fiber around the nails on the outside of the formwork is tedious and time
consuming. In the prototype only one layer of translucent elements was embedded in concrete, thus a
better way of the placement of concrete could be experimented. This could be done using a 6-axis robot
and programming the winding of the fiberglass over hooks in space could allow the process to become
large scale and efficient.
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The 3D printed light transmitting network created for prototype 5 were printed as different layers to form
each of the branches that would pass light across. However, this process of layered 3D printing proved to
be a hinderance to the light transmission quality of the network. Using a thick nozzle could solve this issue
of each branch being printed in various layers. 3D printing a branch as one layer would allow the network
to be translucent and the experiment could be worth experimenting. With this method different
translucent filaments can be experimented with to compare the light transmitting quality to optimize the
amount of light transmitting through the prototype.
Prototype 6 involves the creation of a light transmitting network using epoxy resin and a silicone mold.
This was the first attempt at creating a silicone mold and casting epoxy resin which had multiple issues.
The 3D printed network that was used to make the silicone mold was not well secured to the base of the
wooden formwork which caused the silicone mold to not have clean channels to case the epoxy resin. the
silicone mold was made to the exact width of the concrete prototype that would be thickness of the panel.
This left no room for error at the ends of the light transmitting network. To create a better light
transmitting network, these are issues that can be solved to create a better light transmitting network.
Firstly, the 3D printed network could be well secured to the base using hot glue as well as taped to the
base. This would allow the silicone mold to be created with better channels. The 3D printed geometry
could also be made longer than the desired the length of the prototype. This would allow for the light
transmitting network to be cut to desired length if there are any imperfections on the ends of the panels.
Due to the failure of the light transmitting network when first prepared for prototype 6, the network was
not embedded in concrete. With the issues being worked on to create a better epoxy resin light
transmitting network, its performance in concrete can be explored to realize the light transmission
through the network.
In this research, experimentation was done using materials with radii ranging from 9 microns to 0.125 cm
and this falls in the realm of extremely small diameter light transmitting elements. The next part of the
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research could be to explore the placement of materials that have a larger thickness; these materials could
be extruded acrylic sheets, corrugated acrylic sheets, transparent ceramics.
These methods also involve the placement of the light transmitting elements, as opposed to this, a new
method can be tried out by creating holes in concrete and then filling those holes with a transparent liquid
such as epoxy resin. This would make the manufacture process shorter by eliminating steps. Another
method that can also be explored is to coat these holes with a reflective material like liquid aluminum.
The holes after the aluminum coat can either be left open or filled in with epoxy resin. However, to
understand the potential of these methods would also require the assessment of light transmission
quality, structural strength, durability, etc. The process to make holes in the concrete can be done using
a metallic mold with spikes or long extrusions that lowers into the formwork from one open face (top
face), the concrete then poured into the formwork, allowed to set with the metal spike mold and then the
mold taken out allowing the panel to set with holes.
The 3d printing technology can also be explored and pushed beyond limits. There are many transparent
3d printing materials such as PETG, PLA and ABS. the potential of these materials can be tested out to see
which ones perform the best over time, are the best to print and have the best light transmittance.
Different 3d printers also provide different results that can also be explored to take the material further.
Each 3d printer also has different nozzle attachments that differ in sizes to get thicker or thinner extrusions
or prints. This can have varying results in the matrix being printed as the light transmitting elements.
Chapter 6.2.2 Long term
The existing method used for commercial production of translucent concrete involves the pultrusion
method that forms a translucent acrylic knit fabric that allows light transmission. This research could have
benefitted from the knowledge of how the method works. Documenting the process would allow the
ideation of the other potential translucent materials that can be used for the production of translucent
concrete.
119

Another method that can be explore is the use of a 5-axis or 6-axis robot to wind a flexible material like
GFRC fibers or acrylic fibers across mesh-like elements on the light emitting and receiving edges. This
process would reduce manual labor immensely and create near perfect panels. This method could also
have great potential to make mass produced translucent panels and products.
3d printing light transmitting elements could also be designed in a way that they bring light in from more
than 2 points therefore more light can be brought into spaces. Increasing the radii of the inlet on the light
transmitting element as compared to the outlet or vice versa can also be explored to determine the
change in the amount of light by the change in geometry. This have a result that is analogous to funnel
effect on wind caused by tapering of geometry on one end.

120

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Asset Metadata

Creator Shimpi, Chinmai Shrikant (author)

Core Title A survey and experiments exploring light transmitting concrete

Contributor Electronically uploaded by the author (provenance)

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Degree Conferral Date 2022-08

Publication Date 05/12/2022

Defense Date 05/20/2022

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,optical fibers,translucent concrete

Format application/pdf (imt)

Language English

Advisor Noble, Douglas (committee chair), Ley, Robert (committee member), Schiler, Marc (committee member)

Creator Email cshimpi@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-oUC111313294

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Abstract (if available)

Abstract Light-transmitting concrete or translucent/transparent concrete has gained traction in the last couple of decades using certain specific materials such as optical fibers as the translucent aggregates. These are typically either glass or plastic fibers that are very delicate owing to their small diameters, making the process of production of the translucent concrete blocks extremely tedious requiring highly skilled labor. These limitations in the existing processes of production also makes the material very expensive to be used extensively throughout the world. However, its large-scale use might contribute to significant energy savings worldwide. Thus, efficient methods of production and materials need to be explored and experimented. The findings show that there are better methods and materials such as glass reinforced concrete fibers, 3D printed translucent materials, and epoxy resin framework created by epoxy resin liquid that is poured in molds and allowed to solidify and act as the medium of light transmittance through the panel that can be placed in the concrete. These methods are easier to produce and do not require skilled labor. After performing a light transmission test on the prototypes, the results showed that the light transmittance is high. Thus, translucent concrete as a material, through the new methods of production that have been explored, proves to be improve sustainability by allowing light penetration and reducing the use of energy.