干湿循环作用对混凝土抗氯离子渗透侵蚀性能的影响

为了加速模拟海洋潮差区环境对混凝土耐久性能的影响，掺入矿粉和纳米改性矿物掺合料，研究了氯盐干湿循环作用对混凝土抗氯离子侵蚀性能及微观结构的影响，并将干湿循环试验与常规浸泡试验进行了对比。结果发现，干湿循环作用粗化了混凝土试件表层孔结构，增大了孔径>50 nm的孔隙含量，显著提高了自由及总氯离子浓度；掺入纳米改性矿物掺合料能降低混凝土内部孔隙率，减少有害孔含量，提高混凝土内部氯离子结合能力；干湿循环60天后混凝土表层Ca（OH）₂逐渐被消耗，生成了Friedel盐和CaCO₃。 

Effect of dry-wet cycling on resistance of concrete to chloride ion permeation erosion

In order to accelerate the impact of simulated marine tidal zone environment on the durability of concrete,the mineral powder and nano modified mineral admixture were added,and the effect of dry-wet cycling of NaCl on the resistance to chloride ion erosion and microstructure of concrete was studied,which was compared with the immersion test.The results show that the dry-wet cycling coarsens the pore structure of the concrete surface,increases the pore content of pore size larger than 50 nm and significantly increases the free and total chloride ion concentration;the incorporation of nano-modified mineral admixture can reduce the internal porosity of concrete and the harmful pore content,while can improve the chloride ion binding capacity of concrete.After 60 days of wet and dry cycling,the Ca(OH)2 on the surface layer is gradually consumed,and the Friedel salt and CaCO3 are formed.