Experimental Investigation into the Mechanical and Optical Properties of Transparent Concrete using Plastic Optical Fibers

Sustainable construction increasingly demands innovative materials that reduce building energy consumption without sacrificing functional structural performance. Light-transmitting concrete (LTC), a composite material embedding optical fibers into a fine-grained concrete matrix, offers significant potential for indoor daylighting and architectural applications. However, a critical trade-off exists between optical transparency and mechanical strength, and widespread adoption is hindered by a lack of clarity regarding whether reduced compressive strength meets non-load-bearing structural standards. To address this gap, this study systematically investigates the compressive strength and light transmission efficiency of plastic optical fiber (POF) grids embedded in a fine-aggregate mortar matrix. Three grid arrangements were evaluated: 13x13 (5.00% fiber density), 15x15 (5.72%), and 18x18 (7.00%). Experimental testing using a luxmeter and light-dependent resistor (LDR) setups demonstrated that optical transmission scales directly with fiber density, peaking at 70.30% for the 18x18 grid. Conversely, compressive strength tests at 28 days revealed an inverse relationship with fiber volume: while the 13x13 grid retained a high compressive strength of 9.5 MPa (exceeding the 9.3 MPa control specimen), strength dropped to 7.1 MPa for 15x15 and 5.7 MPa for 18x18. Evaluating these metrics against civil engineering standards reveals that even the lowest-strength 18x18 configuration (5.7 MPa) safely exceeds the baseline compressive strength required for non-load-bearing masonry units and partition walls (3.5–5.0 MPa, e.g., ASTM C90/C129), maximizing daylighting performance. Meanwhile, the 13x13 configuration provides a viable solution for low-stress semi-load-bearing structural applications. These findings establish clear application-specific criteria for LTC, demonstrating its practical viability in energy-efficient green architecture.