玄武岩纤维再生混凝土冻融后的弯曲疲劳特性

Bending fatigue characteristics of frozen-thawed basalt fiber recycled concrete

基于中国北方地区气候特点及混凝土路面的受力特征,研究冻融损伤对玄武岩纤维再生混凝土(BFRC)弯曲疲劳特性的影响。首先对BFRC采用快冻法进行冻融循环试验,研究BFRC的冻融损伤形貌、质量、相对动弹性模量和相对抗折强度的变化;然后针对经历不同冻融循环次数后BFRC的弯曲疲劳特性进行了试验研究,分析了冻融循环次数与应力水平对BFRC疲劳寿命的影响规律;最后基于两参数Weibull分布理论对BFRC的疲劳寿命进行分析,预测了不同失效概率下的疲劳寿命并建立了失效概率为0.05和0.5下的双对数疲劳方程。结果表明:随着冻融循环次数的增加,试件表面损伤程度和质量损失率逐渐增大,相对动弹性模量和相对抗折强度逐渐下降,当冻融循环达到225次时,BFRC的相对动弹性模量和相对抗折强度与冻融循环前相比分别下降了12.4%和35.1%;随着冻融循环次数和应力水平的增加,弯曲疲劳寿命逐渐减小;BFRC经冻融循环后的弯曲疲劳寿命服从两参数Weibull分布,失效概率为0.5的预测疲劳寿命与试验所得平均疲劳寿命十分接近;建立的双对数疲劳方程能较好地反映冻融后BFRC应力水平S与疲劳寿命N之间的关系,研究成果为BFRC在路面结构中的安全应用提供可靠依据。

Based on the climatic characteristics of northern China and the mechanical characteristics of concrete pavement, the influence of freeze-thaw damage on the bending fatigue characteristics of basalt fiber recycled concrete(BFRC) was investigated. Firstly, the fast freezing method was used in the freeze-thaw cycle test of BFRC to investigate the changes of freeze-thaw damage morphology, mass, relative dynamic elastic modulus and relative flexural strength of BFRC. Then, the bending fatigue properties of BFRC after different freeze-thaw cycles were investigated by experiment, and the influence of freeze-thaw cycles and stress levels on the fatigue life of BFRC was analyzed. Finally, the fatigue life of BFRC was analyzed based on two-parameter Weibull distribution theory. The fatigue life of BFRC with different failure probability was predicted and the double logarithmic fatigue equations with failure probability of 0.05 and 0.5 were established. The results show that with the increase of the freeze-thaw cycles, the damage degree of specimen surface and the mass loss rate increase gradually, and the relative dynamic elastic modulus and relative flexural strength decrease gradually. When the times of freeze-thaw cycle reach 225, the relative dynamic elastic modulus and relative flexural strength of BFRC decrease by 12.4% and 35.1% respectively compared with those before freeze-thaw cycle. With the increase of freeze-thaw cycle and stress level, bending fatigue life decreases gradually. The bending fatigue life of freeze-thawed BFRC obeys two-parameter Weibull distribution. The predicted fatigue life with failure probability of 0.5 is very close to the average fatigue life obtained by test. The established double logarithmic fatigue equation can well reflect the relationship between stress level S and fatigue life N of frozen-thawed BFRC. The research findings provide a reliable basis for the safe application of BFRC in pavement structure.