干湿循环作用下混杂纤维再生骨料混凝土抗硫酸盐侵蚀性能研究

Study on the resistance of mixed fiber recycled aggregate concrete to sulfate attack under dry-wet cycles

将聚乙烯醇纤维(PVAF)和玄武岩纤维(BF)以不同比例和不同体积率的方式掺入混凝土中,并用30%再生粗骨料等质量替代普通粗骨料配置混杂纤维再生骨料混凝土,进行90次的硫酸盐干湿循环试验,测量不同干湿循环次数下混凝土的质量损失、相对动弹性模量和抗压强度。研究表明:当硫酸盐干湿循环90次后,单掺PVAF组混凝土质量损失率为0.22%,相较于普通混凝土降低了42%,单掺BF组混凝土质量损失率为0.19%,相较于普通混凝土降低了50%;当PVAF∶BF分别为1∶4,1∶2,1∶1和4∶1,纤维体积率为0.2%时,混凝土的质量损失率最小。硫酸盐干湿循环90次后,当PVAF∶BF为1∶1和2∶1,纤维体积率为0.3%时,混凝土相对动弹性模量降低到最低值,分别为102.2%和99.4%;然而当PVAF∶BF为1∶2,1∶4和4∶1,纤维体积率为0.2%时,混凝土相对动弹性模量降低到最低值,分别为99.4%、94.1%和99.4%。硫酸盐干湿循环90次后,当纤维体积率小于0.2%时,混凝土的抗压强度损失率的大小依次为1∶1混掺<4∶1混掺=1∶2混掺<1∶4混掺<2∶1混掺;当纤维体积率大于0.2%时,混凝土的抗压强度损失率的大小依次为2∶1混掺<1∶2混掺<1∶1混掺<4∶1混掺<1∶4混掺。与单掺PVAF或BF相比,混掺PVAF和BF对混凝土抗硫酸盐侵蚀能力更高,表现出较好的“正效应”。

Polyvinyl alcohol fibers(PVAF)and basalt fibers(BF)were selected to be incorporated into concrete in different proportions and volume rates,and mixed fiber recycled aggregate concrete was configured with 30%recycled coarse aggregate as an equal mass replacement of normal coarse aggregate.90 times dry-wet sulfate cycles tests were conducted to measure the changes in mass loss,dynamic elastic modulus and compressive strength of concrete after different times of dry-wet cycles.The study showed that the mass loss rate of concrete in the PVAF group was 0.22%,which was 42%lower than that of normal concrete,and the mass loss rate of concrete in the BF group was 0.19%,which was 50%lower than that of normal concrete,when PVAF∶BF was 1∶4,1∶2,1∶1 and 4∶1,and the fiber volume ratio was 0.2%,the minimum mass loss rate.When PVAF∶BF was 1∶1 and 2∶1 with 0.3%fiber volume ratio,after 90 times of wet-dry cycles of sulfate,the minimum values of relative dynamic elastic modulus reduction of concrete were 102.2%and 99.4%,respectively;however,when PVAF∶BF was 1∶2,1∶4 and 4∶1 with 0.2%fiber volume ratio,the relative dynamic elastic modulus of concrete was reduced to the lowest values of 99.4%,94.1%and 99.4%.After 90 times of dry-wet cycles of sulfate,when the fiber volume rate was less than 0.2%,the magnitude of compressive strength loss rate of concrete was in the following order:1∶1 mix<4∶1 mix=1∶2 mix<1∶4 mix<2∶1 mix;when the fiber volume rate was greater than 0.2%,the magnitude of compressive strength loss rate of concrete was in the following order:2∶1 mix<1∶2 mix<1∶1 mix<4∶1 mix<1∶4 mix.Mixing PVAF and BF on the concrete resistance to sulfate erosion than single PVAF or BF,showing a better“positive effect”.