Effects of multi-sized glass fiber-reinforced polymer waste on hydration and mechanical properties of cement-based materials

Utilization of recycled glass fiber reinforced polymers (GFRP) is challenging due to their non-degradability and complex composition. This work explored an application route to produce supplementary cementitious material (SCM) and fine aggregate (FA) with mechanical processed GFRP wastes. A novel GFRP-Sand composite fine aggregate (GSCA) was developed with a combination progress of multi-particle size, continuous gradation design and equal volume substitution method. The effects of GFRP waste on the hydration reaction, workability, mechanical properties and micro-structure of cement-based materials were systematically studied. Results showed that GFRP powders can be used as inert fillers with their reactivity index below 60 %. Replacement of 10 wt% GFRP powder did not change the grade of cement. With the replacement of 10∼30 vol% F1 in GSCA, the early compressive strength and flexural strength of mortars increased by 2–7% and 7–16 %, respectively, while the later strength grade of mortars was maintained. The resin component in GFRP SCMs reacted with cement and formed a gel film and the calcite filler reacted with generation of Mc, which improved the binding strength between aggregate and paste. Tiny glass fiber on the surface of GFRP aggregates increased the binding strength of interfacial transition zone (ITZ) in 3 days, while the consumption of calcite induced the separation of glass fiber from GFRP FAs with hydrated time passed. This work could be the basis for understanding the reaction mechanism of GFRP waste in cement-based materials from macro-to micro-scale and addressing an efficient way for its large-scale usage with low cost.