Research on the mechanism of elevated permeability resistance in recycled glass fiber reinforced concrete

In order to address the disposal challenge of waste glass fiber composite materials and provide a feasible reference for the utilization of recycled glass fiber (RGF), contributing to the sustainable development of concrete engineering. This study focuses on the reuse of RGF to reinforce the impermeability of concrete. The effects of thermal treatment temperature on the properties of RGF are studied and the microstructural morphology of RGF and its reinforcement effect to concrete are evaluated. Additionally, the permeability resistance of recycled glass fiber reinforced concrete (RGFRC) is investigated, and the mechanism of elevated permeability resistance in RGFRC is revealed. Results indicate that with increasing thermal treatment temperature, the diameter of the thermal treated RGF is notably reduced and the surface of the fiber is covered with a significant amount of impurity. When thermal treated under 600 °C, the RGF presents the optimal structure with appropriate surface roughness, higher crystallinity, stable molecular structure, good compactness. Thus the concrete with RGF calcinated under 600 °C demonstrates the highest compressive strength, demonstrating that the optimal thermal treatment temperature is around 600 °C. Furthermore, the concrete exhibits a continuous reduction in internal water penetration height and sustained improvement in permeability resistance as the fiber content increases. The mechanism behind the improved impermeability of RGF to RGFRC lies in the interweaving of RGF within the concrete matrix, forming a three-dimensional network structure. This structure partially inhibits crack formation and pore expansion, effectively reducing the continuity of interconnected pores, decreasing the size of voids and cracks, and slowing down water permeation, thereby enhancing the impermeability of concrete.