Impacts of Water Saturation on the Mechanical Behavior of Basalt/Glass Fiber-Reinforced Recycled Aggregate Concrete Under Varying Stresses: Insights from Macro and Micro Perspectives

Abstract

Recycled aggregate concrete (RAC) offers an effective approach to reducing the environmental burden associated with construction and demolition waste. In this study, a fiber-reinforced RAC was developed by replacing part of the cement with fly ash and ground granulated blast-furnace slag, while glass fibers or basalt fibers were incorporated as reinforcing materials. A systematic experimental program was conducted to evaluate the mechanical behavior of the proposed concrete under different saturation conditions. The results show that the best toughness performance was achieved in the natural moisture state. In comparison, compressive and flexural strengths reached their maximum values under dry conditions, whereas splitting tensile strength peaked in the natural state. Based on the experimental data, prediction equations were established for the splitting tensile and flexural strengths by considering both saturation degree and fiber content. A stress–strain model under uniaxial compression was also developed. In addition, scanning electron microscopy (SEM) was employed to examine the fiber–matrix interface and hydration products, thereby clarifying the microstructural characteristics of the concrete at different saturation levels.