中文摘要：

C30和C50引气混凝土在3．5％NaCl以及5％Na2SO4＋3．5％NaCl溶液中自然浸泡或快速冻融循环，测试盐冻过程中混凝土不同深度粉末浸泡液的pH值及腐蚀产物。结果表明：盐冻过程中混凝土发生溶蚀，其表层的pH值、氢氧化钙和C—S—H量低于内部。随冻融循环次数增加，混凝土溶蚀深度和pH值下降幅度增大。复合溶液中硫酸根离子存在延缓了混凝土表层溶蚀，致使其pH值下降幅度减轻。浸泡环境下，混凝土表层pH值降低幅度约为冻融环境的50％。提高混凝土强度不仅增加其自身碱度，而且提高了混凝土致密度，有助于提升其在盐冻过程中的抗溶蚀能力。

英文摘要：

The pH value and corrosion products of concretes under attack of chloride salt frost or immersion are systematically investi-gated.The compressive strength grade of concrete is C30 and C50.The corrosion regimes are employed in this study：freeze-thaw cycles in 3.5% NaCl solution or in 5%Na2SOn＋3.5%NaCl solution,and naturally immersion（stored in corrosion solution with same time of freeze-thaw cycles）.The experimental results show that value ofpH, Ca（OH ）2 and CSH content in the surface zone are less than that in inner zone of con- crete subjected chloride salt frost.The dissolution depth and pH value drop of concrete enlarge with increasing freeze-thaw cycles.The sul-fate ion in composite solution delays the dissolution speed and retards the pH value drop of concrete in chloride salt environment.When concrete immerses in chloride solution, the pH value drop of surface zone is 50% of concrete subjected to chloride salt frost.Additionally, higher compressive strength grade of concrete, higher pH value and compactness of concrete, which is help to improve the dissolution re-sistance capacity of concrete subjected to salt frost.