超高性能混凝土高温后残余力学性能试验研究

Experimental study on residual mechanical properties of ultra-high performance concrete exposed to high temperature

测定了抗压强度高于140MPa的含粗骨料超高性能混凝土和活性粉末混凝土遭受高温作用后的残余抗压强度、残余劈裂抗拉强度和残余断裂能。结果显示,两种超高性能混凝土的残余强度均随着目标温度的升高而呈现先增大再降低的趋势,而残余断裂能均随着目标温度的升高逐渐降低。各目标温度下,含粗骨料超高性能混凝土的残余抗压强度均高于活性粉末混凝土,但其残余劈裂抗拉强度和断裂能低于后者。活性粉末混凝土在300℃临界温度下的峰值残余抗压强度和峰值残余劈裂抗拉强度分别比常温时提高了26.8%和19.3%,800℃高温后的强度损失率分别为72.3%和81.4%。含粗骨料超高性能混凝土在400℃临界温度下的峰值残余抗压强度和在300℃目标温度下的峰值劈裂抗拉强度分别比常温时提高了34.0%和6.8%,800℃高温后的强度损失率分别为70.2%和84.9%。所以,对于有抗火灾高温要求的工程结构,含粗骨料超高性能混凝土适合用于受压构件,而活性粉末混凝土适宜于抗弯构件。

Ultra-high performance concrete with coarse aggregate （UHPC-CA） and reactive powder concrete （RPC）, with a compressive strength of over 140 MPa, were exposed to high temperature for determining their residual compressive strengths, splitting tensile strengths and residual fracture energies experimentally. The results indicate that at each target temperature, the residual compressive strength of UHPC-CA was higher than that of RPC, but the residual splitting tensile strength and fracture energy of UHPC-CA were lower than those of RPC. With the increase of target temperature, the residual strength of both ultra-high performance concretes increased first and then decreased, while the residual fracture energy of both concretes decreased. Compared to unheated specimens at room temperature, the increases of the peak residual compressive strength and the peak residual splitting tensile strength of RPC specimens at the critical temperature of 300℃ were 26.8% and 19.3% , respectively, while those the corresponding increases of the two strengths of UHPC-CA subjected to the critical temperature of 400℃ and the target temperature of 300℃ were 34.0% and 6.8%, respectively. After experiencing the high temperature of 800℃, the losses in compressive strength and splitting tensile strength of RPC were 72.3% and 81.4% , respectively, while those of UHPC-CA were 70.2% and 84.9%. The results suggest that for building structures with fire-resistance requirements, UHPC-CA should be used in compression members, while RPC is more appropriate for bending-resistant members.