Natural light transmittance of light-transmitting concrete (LTC) incorporated with optical fibres

Abstract

This paper focused on investigating the light transmittance properties of light-transmitting concrete (LTC) under sunlight. Self-compacting concrete (SCC) and polymethylmethacrylate (PMMA) optical fibres with fibre diameter of 2 mm were used to fabricate LTC blocks. Since fibre spacing, LTC surface area, and light incidence angle are important factors which affect the light transmittance, but are rarely investigated in previous studies, the current study used fibre spacing of 15 mm, 18.75 mm, and 25 mm, and different LTC surface area, altered by placing one to six blocks together, to investigate the effects on light transmittance of LTC under sunlight. The light transmittance tests were conducted on a sunny day from 9 a.m. to 4p.m. A light meter was used to measure the intensity of light transmitted by the LTC. Fresh properties tests of SCC and compression tests on LTC were also conducted. The results show that LTC incorporated optical fibres had lower compressive strength compared to the control concrete block. The difference in fibre spacing has no significant effect on the compressive strength of LTC. The light transmittance of LTC with a spacing of 15 mm has the best light transmittance performance among the LTC blocks with different fibre spacing. The increment of light transmittance was approximately 24% to 28% near solar noon, when the LTC surface area increased from one block to six blocks regardless of the fibre spacing. It was found that the light transmittance declined drastically when the light incidence angle was beyond the acceptance angle. Further research is needed on LTC that takes into account the distance between the light meter and the LTC block to obtain a more comprehensive understanding of light transmittance before it is applied in building construction, with the aim to reduce light energy consumption.