聚丙烯粗纤维喷射混凝土冻融性能研究

On the Freezing-Thawing Mechanism of Macro-PP Fiber Shotcrete

为了研究聚丙烯粗纤维喷射混凝土在寒区隧道结构中应用的可行性,文章采用饱水快速冻融试验方法,得到了聚丙烯粗纤维喷射混凝土的质量损失率以及相对动弹性模量;根据冻融试验结果,分析了聚丙烯粗纤维喷射混凝土冻融破坏机理,建立了聚丙烯粗纤维混凝土的冻融损伤模型,并对其在自然条件下和隧道环境内的寿命进行了预测。研究结果表明:在提高抗冻性能方面,纤维最优体积率在0.9%左右;纤维对混凝土的抗冻性能是在纤维阻裂与纤维软弱界面两种作用下产生的结果;采用双段预测模型能有效地预测聚丙烯粗纤维混凝土的冻融循环次数,对我国不同地区喷射混凝土的寿命进行预测,可以作为聚丙烯粗纤维喷射混凝土耐久性定量设计的依据。

In order to study the feasibility of applying Macro-PP fiber shotcrete to tunnels in cold regions, the mass-loss ratio and relative dynamic elastic modulus of freezing-thawing experimental method. According to the damage was analyzed and a freezing-thawing damage Macro-PP fiber shotcrete were obtained using a rapid experiment results, the mechanism of freezing-thawing model of Macro-PP fiber shotcrete was established. Additionally, the life of Macro-PP fiber shotcrete under natural conditions or inside a tunnel was predicted. Research results show that： 1） the optimal volume rate of the fibers is about 0.9% for improving the freeze- resistance performance; 2） the anti-freeze effect of fibers on the concrete was produced under the actions of both fiber crack-resistance and a weak fiber interface; 3） using the two-stage prediction model can effectively predict the freezing-thawing cycles of Macro-PP fiber shotcrete, as well as shotcrete life for different regions of China, which can be used as the basis for the durability design of Macro-PP fiber shotcrete.