Sustainable translucent geopolymer concrete based on metakaolin and recycled glass

In this study, a new translucent geopolymer concrete (TGPC) was developed using recycled crushed glass as a partial fine aggregate substitute and metakaolin as the only binder to combine sustainability with architectural functionality. This paper presents an eco-innovative system that simultaneously optimizes the structural, optical, and thermal properties, in contrast to traditional translucent concrete that uses Portland cement and virgin optical fibers. Alkali-resistant glass fibers (ARGF), coated and uncoated optical glass fibers (OGF), and crushed glass (0–60%) were included in different amounts in the six mix designs. Extensive tests were performed, including scanning electron microscopy (SEM) microstructural analysis, light transmittance, thermal conductivity, compressive strength, and flexural strength. The optimum proportion (T3), based on the data obtained, reached a unique synergy between strength, transparency, and thermal insulation with a compressive strength of 35.8 MPa, bending strength of 5.0 MPa, light transmission of 2.2%, and lower thermal conductivity of 0.686 W/m·K. Based on the SEM analysis, early interface degradation was noted on the uncoated fibers, but the fluoropolymer-coated OGF retained robust fiber-to-matrix adhesions. This work is original in the context of the first study that employed a unique combination of recycled glass materials, fluoropolymer-coated fibers, and a metakaolin binder with lower carbon emissions. These data show that TGPC is an alternative material suitable for ecologically concerned and energy-efficient daylighting architectural technologies.