Analysis of Splitting Tensile Damage Behavior and Deterioration Mechanism of Aluminate Cement-Based Ultrahigh-Performance Concrete under Simulated Fire Temperatures
Traditional portland cement (PC)-based ultrahigh-performance concrete (UHPC) is prone to spalling under fire temperatures due to its dense microstructure, accompanied by severe performance degradation, which hinders its widespread application in engineering. Therefore, this study developed an aluminate cement-based UHPC (AUHPC) with excellent high-temperature resistance and antispalling performance, and systematically investigated the effects of steel fiber type, content, and exposure temperature on the compressive and splitting tensile properties. The results indicate that steam and dry-heat curing effectively inhibit the strength retrogression caused by the transformation of CAH 10 to C 3 AH 6 . Meanwhile, with the increase in temperature, recycled brick powder (RBP) participates in the hydration reaction and forms stable C 2 ASH 8 . At 400°C, the compressive and splitting tensile strengths of AUHPC specimens containing 5% RBP reach the maximum, with the strength of RSF2 specimens increasing by 37.2% and 46.3%, respectively, compared with that at room temperature. When the temperature exceeds 600°C, the number of pores on the specimen surface decreases gradually, while the cracks increase and widen. At 800°C, the splitting tensile strength of NSF2 and RSF2 series specimens decreases by 44.6% and 7.9%, respectively, compared with that at 20°C. At 1,200°C, the holes and channels left by the complete melting of normal steel fibers (NSF) aggravate the high-temperature damage, and the strength decreases with the increase of NSF content, while refractory steel fibers (RSF) exhibit better compatibility with AUHPC matrix.