混合砂对C60海工混凝土耐久性的影响及机理分析

Influence and Mechanism Analysis of Composite Sand on Durability of C60 Grade Marine Concrete

采用级配不合格的机制砂与河砂按一定比例混合后得到了合格的混合砂,研究了不同比例组成的混合砂对混凝土耐久性的影响,并采用化学结合水法、热重分析法以及SEM等测试方法分析了混合砂对混凝土耐久性的影响机理,结果表明:混合砂混凝土试件的氯离子扩散系数要低于纯河砂混凝土试件,且混凝土氯离子扩散系数的变化趋势是随机制砂比例的提高而降低;混凝土的抗硫酸盐耐蚀系数随机制砂比例的提高而降低,原因是提高机制砂的比例会提高混凝土的密实度,导致抗压强度比变化不大;不同比例组成的混合砂的级配不同,同时混合砂中的石粉可参与胶凝材料的水化进程,混合砂对混凝土耐久性的影响是这两因素的综合体现。

The mixed sand was produced by mixing the manufactured sand with unqualified grading and the river sand according to the certain proportion. Then the influence of mixed sand with different ratio of river sand to manufactured sand on chloride diffusion coefficient and sulfate corrosion resistance coefficient for hardened concrete was investigated, and the mechanism of effect of mixed sand on durability of C60 marine concrete was investigated by using Chemical Combined Water Test, TG Test, and SEM in this work. The results showed that the chloride diffusion coefficient and the sulfate corrosion resistance coefficient for hardened concrete decreased with the increasing of the proportion of manufactured sand in the mixed sand, but the sulfate corrosion resistance coefficient was higher than 0.99 in this research. Furthermore, the influence of mixed sand on durability of concrete was reflected in two aspects： the fine aggregate gradation changed with the changing of the proportion of river sand in mixed sand, and the stone dust in mixed sand improved the hydration of cement.