超高性能混凝土在环境温度变化下的力学性能试验研究

Experiment study on mechanical properties of ultra-high performance concrete under ambient temperature change

应用四点抗弯、轴压、轴拉实验,研究环境温度变化(-30℃、0℃、30℃、60℃、90℃)对超高性能混凝土(UHPC)力学性能的影响,通过数字图像技术(DIC)表征受弯过程中裂缝的发展,并结合SEM、压汞(MIP)对其微观结构进行分析。结果表明:经历不同环境温度变化后,UHPC弯拉、抗压、轴拉强度分别处于13.4-16.3 MPa、121.5-133 MPa、6.6-7.0 MPa范围,轴拉应变约为0.2%;与基准温度(30℃)相比,低温作用对其力学性能几乎无影响,随温度的升高性能有一定降低,但仍处于较高的水平;弯拉强度和轴拉强度在不同环境温度下都大致存在比例系数约为2.3的线性关系;30℃下基体更加致密,拥有最优的力学性能。

Four-point bending, uniaxial compressive and tensile tests were employed to explore the effects of the change of ambient temperatures(-30℃、0℃、30℃、60℃、90℃) on the mechanical properties of the ultra-high performance concrete(UHPC). The propagation of cracks during bending process was monitored by a digital image correlation(DIC) technology, and SEM and mercury intrusion porosimetry(MIP) were conducted to analyze the microstructure. The results show that the bending, compressive and tensile strengths of UHPC are within the range of 13.4-16.3 MPa, 121.5-133 MPa and 6.6-7.0 MPa, respectively, after subjected to different ambient change of temperatures. The tensile strain keeps almost consistent around 0.2%. Compared with standard temperature(30℃),the low temperature has little impact on the mechanical properties of UHPC, while the properties decrease with the temperature increasing, nevertheless, still at a higher level. The flexural strength and uniaxial strength present approximately linear relationship with proportionality coefficient of 2.3 at different temperatures. The matrix of UHPC at 30℃ is relatively denser, and thus possesses optimal mechanical properties.