碳化对混凝土中氯离子扩散的影响

混凝土与静浆快速碳化0,14,28d后浸泡到3.5%NaCl溶液中650d,测试了混凝土不同深度的自由氯离子、总氯离子含量,计算出混凝土的表观氯离子扩散系数和氯离子结合能力;采用压汞法测试了不同腐蚀制度下静浆表层的孔结构,利用DSC分析了静浆的腐蚀产物.结果表明:混凝土碳化后浸泡到腐蚀溶液中,增加了混凝土中的氯离子含量,提高了混凝土表观氯离子扩散系数,降低了混凝土对氯离子的结合能力;且随碳化时间的增加,变化幅度变大.快速碳化粗化了混凝土的孔结构,其大于30nm的毛细孔数量增加了11%,最可几孔径增加了17nm;降低了混凝土中Friedel'S生成量,以及混凝土对氯离子的化学结合能力.

Effect of carbonation on chloride diffusion in concrete

Concrete and paste were immersed in a 3.5% NaCl solution for 650 d after they were quickly carbonated for 0, 14 and 28 d. The free and total chloride contents in different depths of concrete were tested to calculate the chloride apparent diffusion coefficient and the chloride binding capacity. The pore structure and corrosion production of paste attacked by different corrosion regimes were analyzed by mercury intrusion porosimeter (MIP) and differential thermal analysis (DSC), respectively. The results indicate that the chloride content and the chloride apparent diffusion coefficient increase after quick carbonation, however the chloride binding capacity of concrete reduce simultaneously; and the carbonation influence increase with time. Quick carbonation of concrete coarsens its pore structure that the capillary pore (≥ 30 nm) amount of paste increases by 11% and the most probable pore size increases by 17 nm, but it decreases the Friedel'S amount in concrete and reduces the chemical chloride binding capacity of concrete.