碳-玻璃混杂纤维混凝土抗盐冻性能试验研究

为研究碳-玻璃混杂纤维混凝土抗盐冻性能,文章对不同纤维掺量的混凝土开展了力学性能试验及冻融循环与氯盐、硫酸盐耦合作用下的耐久性试验,测定了抗压强度、劈裂抗拉强度和抗折强度,并探究质量损失率和相对动弹性模量的变化规律。结果表明:单掺或混掺纤维能小幅度提高抗压强度,显著提高劈裂抗拉强度和抗折强度;随着循环次数的增加,质量损失率增大,相对动弹性模量减小;2种纤维混杂能有效改善混凝土抗盐冻性,其中CF30GF30抗盐冻性能最佳。结合扫描电子显微镜(scanning electron microscope, SEM)表征结果分析了纤维改善混凝土抗盐冻性能机理,并基于相对动弹性模量建立了盐冻损伤模型来评价纤维混凝土的损伤程度,发现二次函数衰减模型拟合的相关系数较高,可准确反映盐冻循环作用下混凝土损伤变化规律。

In order to study the salt freezing resistance of carbon-glass hybrid fiber reinforced concrete, this paper carried out mechanical performance test and durability test under freeze-thaw cycle coupled with chloride and sulfate on concrete with different fiber contents, determined the compressive strength, splitting tensile strength and flexural strength, and explored the variation rules of mass loss rate and relative dynamic elastic modulus. The research results show that single or mixed fibers can increase the compressive strength to a small extent, and can significantly increase the splitting tensile strength and flexural strength; with the increase of the number of cycles, the mass loss rate increases and the relative dynamic elastic modulus decreases; the mixing of the two kinds of fibers can effectively improve the resistance to salt freezing of concrete, of which CF30GF30 has the best resistance to salt freezing. Combined with the scanning electron microscope (SEM) results, the mechanism of fiber to improve the salt freezing resistance of concrete was analyzed. A salt freezing damage model based on the relative dynamic elastic modulus was established to evaluate the damage degree of fiber concrete, and it is found that the correlation coefficient fitted by the quadratic function attenuation model is high, which can accurately reflect the variation rule of concrete damage under the action of salt freezing cycle.