Translucent Concrete: Test of Compressive Strength and Transmittance

Translucent Concrete: Test of Compressive Strength and Transmittance

A. Karandikar

1Student (BE/1430/2011),

Department of Civil & Environmental Engineering, Birla Institute of Technology,

Mesra 835215, Jharkhand, India

1. Deep

   N. Virdhi

   Student (BE/1530/2011),

   Department of Civil & Environmental Engineering, Birla Institute of Technology,

   Mesra 835215, Jharkhand, India

   3Student (BE/1515/2011),

   Department of Civil & Environmental Engineering, Birla Institute of Technology,

   Mesra 835215, Jharkhand, India

   Abstract – Translucent concrete allows light to pass through it because of the presence of optical fibers within the opaque concrete wall. Light is transmitted from one surface of the said wall to the other, because of the presence of optical fiber strands along the width of the wall, which allows light to pass through.

   The principal objective of this project is to design translucent concrete blocks with the use of glass optical fibers, and then analyze their various properties and characteristics. All tests further performed on our concrete samples and on the optical fibers as such were done to ascertain the improvements of the casted blocks over normal concrete blocks of the same size and with the same design ratios, and to ascertain the practical utility of using translucent concrete as a building material for green building development.

   Keywords: Optical fibers, Translucent concrete, Compressive strength, Transmittance

   1. INTRODUCTION

      Translucent lightweight Concrete is a new material with various applications in the construction field, architecture, decoration and even furniture. As can be imagined, concrete with the characteristic of being translucent will permit a better interaction between the construction and its environment, thereby creating ambiences that are better and more naturally lit, at the same time as significantly reducing the expenses of laying and maintenance of the concrete.

      Thousands of optical filaments are arranged side by side on a concrete base leaving the light to pass from one side to the other. Due to the small thickness of these filaments, they combine with the concrete. Compared with a traditional electric lighting system, illuminating the indoors with daylight also creates a more appealing and healthyenvironment for building occupants.

      In 2001, Hungarian architect Aron Losonczi invented LiTraCon, the first commercially available form of TC which can allow 80% light through and only 30% of weight of common concrete. It was a combination of optical fibers and fine concrete, combined in such a way that the material was both internally and externally homogeneous. It was manufactured in blocks and used primarily for decoration. LiTraCon presents the concept of light transmitting concrete in the form of a widely applicable new building material. It can be used for interior or exterior walls, illuminated pavements or even in art or design objects.

      Our project of casting translucent concrete aims at analyzing the amount of transmittance and compressive strength of samples by varying the percentage by volume of optical fiber strands. We have used percentages by volume of glass optical fibers of 0.00 %, 0.09 %, 0.87 %,

      1.05 % and 1.75 % respectively.

   2. LITERATURE STUDY

      TABLE-1 : SIEVE ANALYSIS FOR FINE AGGREGATES
      Total Weight Taken = 1000 grams
      S.No.	Sieve Size	Weight Retained (g)	Weight Passing (g)	Cumulative Weight % Retained	Total % Passing
      1	10 mm	0	0	1000	100
      2	4.75 mm	0	0	1000	100
      3	2.36 mm	155.48	155.48	15.548	84.452
      4	1.18 mm	249.84	405.32	40.532	59.468
      5	600 micron	237.88	74.320	64.20	35.680
      6	300 micron	141.88	785.08	78.508	21.498
      7	150 micron	214.92	1000.00	1000.00	0

      Momin et. Al1constructed a lux meter to measure the transmittance of the light passing through the concrete blocks. A Light Dependent Resistor was used to measure the amount of light going through. He, Zhou and Ou2concluded that the larger the POF volume ratio was, the smaller the compressive strength of the translucent concrete was observed. So endlessly increasing the transmittance by way of increasing the POF volume ratio is not possible, as it would have a detrimental effect on the casted cubes mechanical properties.Zhou et. Al3reported that the failure loads obtained for concrete blocks having 3.14%, 3.80% and 4.52% of POF by volume were found to be 201.0 kN, 195.7 kN and 182.2 kN, as opposed to a failure load of 201.8 kN for a conventionally casted concrete block of the same dimensions. This marked a decrease in compressive strength of 0.379%, 3.023% and 9.712% for the concrete blocks having 3.14%, 3.80% and 4.52% of POF by volume, respectively.Shanmugavadivu et. Al4reported that the mix proportions use by them to construct translucent concrete blocks were as follows:Cement- 360 kg; Sand- 560 kg; Fiber- 4.5 kg; Water- 190 l.Germano5, in his official patent for translucent lightweight concrete, stated that the translucent lightweight concrete blocks properties to have thermal resistance, acoustic behavior, higher possibility of finish, weight and higher durability under freeze-unfreeze conditions would allow it to be used for interior and exterior decoration.

   3. SIGNIFICANCE OF STUDY

      • To study the change in concrete properties on the introduction of glass optical fibers.

      • To check the transmittance of the translucent concrete thus produced.

   4. EXPERIMENTAL INVESTIGATION

      1. Materials Used

         Ordinary Portland Cement (Specific Gravity: 3.14), Sand and Glass Optical Fibers were used for the project.

         The diameter of the glass optical fibers was 350 µ.

         From table 1, fineness modulus can be found to be 2.989 (which should be between 2.2 and 3.5 for fine aggregates, hence it is safe to proceed.)

      2. Mix Proportions

         Cement = 490 kg/ m3; Sand = 1489 kg/ m3;Water = 220 liter;Water to cement ratio = 0.45

      3. Manufacturing Process

         The manufacturing process of translucent concrete is almost same as regular concrete. Only optical fibers were placed together with the help of clay along with aggregate and cement mix. Small layers of the concrete are poured on top of each other and infused with the fibers and are then connected. Thousands of strands of optical fibers are cast into concrete to transmit light. Since manually splicing the optical fibers is a tedious task, a mechanical grinder was used for cutting the ends of the translucent concrete, owing to the absence of a splicing machine.

         Figure 1: Translucent Concrete Cubes

      4. Compressive Strength

         Figure 2: Faiure of Concrete Sample

         Compressive strength is defined as the maximum compressive load a body can bear prior to failure, divided by its cross sectional area.

      5. Transmittance

         Cement : Sand : Water
         1	3.039	0.450

         1. Circuit Diagram

         2. Arrangement of Circuit for Test

      Figure 3: Transmission Test

      Transmittance can be directly calculated by the ratio of incident energy and transmission energy of light expressed as the following equation:

      The sample during the experiment was placed at 20 cm or

      0.2 m from the light source which was giving 1750 lumens of luminous flux therefore illuminance can be calculated as:

      I = 1750/ (4(0.2)2 )

      Therefore, I = 3481.5 lumen/m2 (lux)

      Following empirical relation exists between resistance of photo resistor and light intensity:

      Light Intensity (lux) = ()

   5. RESULTS AND DISCUSSION

      1. Compressive Strength

         TABLE 2: COMPRESSIVE STRENGTH TEST RESULTS
         S.N o.	No. Of Fibers	Percentag e Of Optical Fibers (By Volume)	Load (in kg)	Compressive Strength (in N/mm2)	Average Compressive Strength (in N/mm2)
         1	0	0	15000	26.160	27.9040
         			15500	27.032
         			17500	30.520
         2	400	0.09%	15500	27.032	28.1946
         			15500	27.032
         			17500	30.520
         3	4000	0.87%	12000	20.928	21.5093
         			13000	22.672
         			12000	20.928
         4	4800	1.05%	12000	20.928	18.8933
         			10500	18.312
         			10500	18.312
         5	8000	1.75%	10000	17.440	16.8587
         			9500	16.568
         			9500	16.568

         As can be clearly seen from the table, the compressive strength increased in the case for the 0.087% optical fibers by volume sample, but then, it went on to decrease later, as is shown in the following figure.

         Where,

         A, B, C are variables which depend on type of photo resistor; R is the resistance

         For used model after calibrations following relationship was established:

         A=1, B=80, C= -1

         Therefore I (intensity in lux) = 80

         ( )

         Thus, a relationship can be established between the change in resistance and the number of optical fibers used.

         Figure-4: Compressive Strength vs. % Optical Fibers

      2. Transmittance

      TABLE 3: TRANSMISSION TEST RESULTS

      As can be clearly seen from the table, the average transmission of light increased continuously on increasing the number of optical fibers, as is shown in the following figure.

      Figure-5: Avg. Transmittance vs. % Optical Fibers

   6. CONCLUSIONS

1. The transmittance obtained for the various translucent concrete specimens was seen to increase with the amount of optical fibers used. But it came at a price, as the compressive strength started decreasing at a steady rate once the percentage of optical fibers by volume was increased within the concrete samples. Hence, we can conclude that the best value for use commercially can be calculated as 0.9374%optical fibers by volume, which gives us a compressive strength as high as 20 N/mm2.

2. It is known that optical fibers as such are very costly, and we were fortunate to obtain scrap optical fibers from U.M. Cables, Silvassa, for free. But the price of a

200 m spool of single-mode optical fibers in the market today is Rs. 570. Now, for our ideal optical fiber percentage, the no. of wires used would amount to 4596 fibers of 7.5 cm length, which would amount to 344.67 m. Therefore, the market expenditure on optical fibers alone would be Rs. 982.31, and that too for a cube of dimensions 7.5 cm x 7.5 cm x 7.5 cm.

ACKNOWLEDGEMENTS

We welcome this opportunity to express our heartfelt gratitude and regards to, Dr. M.K. Sinha, Department of Physics, Birla Institute of Technology, Mesra, and

Usha Martin Cables, Silvassa, for helping us understand the physics behind optical fibers and for providing us scrap value optical fibers, respectively.

REFERENCES

1. Momin, A., Kadiranaikar, R., Jagirdar, V. & Inamdar, A., Study of Light Transmittance of Concrete Using Optical Fibers and Glass Rods, Proceedings: International Conference on Advances in Engineering & Technology 2014.

2. He, J., Zhou, Z. & Ou, J., Study on Smart Transparent Concrete Product and Its Performances, Proceedings: The 6th International Workshop on Advanced Smart Materials and Smart Structures Technology 2011.

3. Zhou, Z., Ou, G., Hang, Y., Chen, G. & Ou, J., Research and Development of Plastic Optical Fiber Based Smart Transparent Concrete, SPIE, vol. 7293, no. F, 2009

4. Shanmugavadivu, P., Scinduja, V., Sarathivelan, T. & Shudhesamithronn, C., An Experimenal Study of Light Transmitting Concrete, IJRET, vol. 3, no. 11, 2014.

5. Germano, J., "Translucent Lightweight Concrete". Europe Patent EP2410103, 2012.