Study on the Evolution Law of Mechanical Properties of the Modified High Strength BF-RCC Subjected to High Temperature

Basalt fiber-reinforced cementitious composites (BF-RCC) have attracted considerable research interest in construction engineering owing to their excellent mechanical performance. However, some great challenges, such as limited ultimate tensile strain (typically less than 1%) and poor high-temperature resistance, have restricted its broader application. This study explores the influence of silane coupling agent (SCA) modification on the mechanical performance of the BF-RCC under high-temperature environments. The basalt fibers were treated with KH602 (SCA) to enhance interfacial bonding with the cement matrix under high-temperature environments. The mechanical performance of BF-RCC, including tensile strength, compressive strength, elastic modulus, crack propagation behavior and toughness index, was evaluated under different SCA concentrations (2.5% and 4.5%) and different temperatures (20 °C, 200 °C, 300 °C and 400 °C). The findings demonstrate that the tensile strength and compressive strength of the BF-RCC are elevated by 1.5 times and 1.7 times, respectively, while the toughness index and elastic modulus are enhanced by 1.6 times and 1.4 times, respectively. The incorporation of SCA significantly reduces the mass loss of the BF-RCC under high temperatures, with the 2.5% KH602 concentration exhibiting the optimal performance. However, when the temperature exceeds 300 °C, the mechanical properties of the BF-RCC deteriorate markedly. Digital image correlation (DIC) technology demonstrated that SCA-modified BF-RCC displays enhanced crack propagation resistance, with post-peak fracture energy showing a concentration-dependent increase, thereby reducing material brittleness.