活性粉末混凝土高温后强度退化规律试验研究

Experimental Research on Strength Degradation Law of Reactive Powder Concrete after Elevated Temperatures

为研究活性粉末混凝土(RPC)高温后强度退化规律,对高温后RPC试件的质量损失、抗压性能和劈裂抗拉性能进行测试,并分析温度和纤维掺量对RPC强度的影响。结果表明:随着温度的升高,RPC试件的表观颜色由深逐渐变浅,质量损失率逐渐增大;而强度损失率均随着温度升高呈先减小后增大的趋势,但临界温度不同,立方体抗压强度和劈裂抗拉强度的临界温度为300℃,而轴心抗压强度的临界温度为200℃,此外,300℃后轴心抗压强度损失率高于立方体抗压强度,800℃后强度损失率均超80%,宏观强度退化的根本原因是基体微观形貌的劣化;掺有聚丙烯(PP)纤维的RPC试件高温后强度损失率相对较小,且当钢纤维掺量为2%(体积分数)时,PP纤维的最佳掺量为0.15%(体积分数)。通过回归分析,建立了RPC强度损失率与温度和PP纤维掺量间的计算公式。

To study the strength degradation law of reactive powder concrete(RPC) after elevated temperatures, the mass loss and compressive strength as well as split-tensile strength of RPC specimens after elevated temperatures were measured. Besides, the effects of temperature and fiber content on the strength of RPC samples were analyzed. The results show that the apparent color of RPC specimens gradually changes from dark to light, and the mass loss rate gradually increases with the rising temperature. The cubic strength loss rate and split-tensile strength loss rate as well as axial compressive strength loss rate all decrease first and then increase with the increasing temperature, but the critical temperature is different. The critical temperature of cube compressive strength and split-tensile strength is 300 ℃, while the critical temperature of axial compressive strength is 200 ℃. In addition, the loss rate of axial compressive strength is higher than that of cubic compressive strength after 300 ℃, and all the strength loss rates exceed 80% after 800 ℃. Deterioration of matrix microstructure is the root cause of macroscopic strength degradation. Moreover, the strength loss rate of the RPC specimen mixed with polypropylene(PP) fiber is relatively small after elevated temperature. When the steel fiber content is 2%(volume fraction), the optimal content of PP fiber is 0.15%(volume fraction). Finally, the calculation equation between the strength loss rate of RPC and temperature as well as PP fiber content was established through regression analysis.