在不同溶液中混凝土对氯离子的固化程度

CHLORIDE BINDING IN CONCRETE EXPOSED TO CORROSIVE SOLUTIONS

研究了不同粉煤灰、矿粉、硅灰掺量的混凝土在单一氯盐、复合溶液以及青海盐湖卤水溶液中的氯离子结合规律。结果表明:混凝土在氯盐溶液中结合氯离子的产物为Friedel’s盐,其在NaCl腐蚀溶液中的氯离子结合能力最大,复合溶液和青海盐湖卤水溶液中由于硫酸根离子的存在降低了混凝土的氯离子结合能力,且随腐蚀溶液中的硫酸盐浓度增加而降低。普通混凝土在青海盐湖溶液中腐蚀,其氯离子结合能力在0.15左右;粉煤灰、矿渣和硅灰混凝土的氯离子结合能力分别为0.13～0.24,0.25～0.40和0.20～0.34。混凝土中掺加20%粉煤灰,或35%矿渣以及8%硅灰对氯离子具有最大的结合效果。此外,还使用热分析和X射线衍射技术研究了上述规律产生的微观机理。

Chloride binding in concretes, which included plain concrete containing Portland cement alone and concretes with 0-50% of fly ash added, 0-65% of ground granulated blastfurnace slag （GGBS） added and 0-12% of silica fume added, was systematically investigated under corrosive solutions. The corrosive solutions included four types： 3.5%NaCl solution, composite solutions of 3.5%NaCl and 5.0%Na2SO4 （or 5.0%MGSO4） and Qinghai salt lake solution. The experimental results show that Friedel＇s salt is the main chloride binding product in concrete, and the chloride binding capacity of concrete is higher for concrete submerged in NaCl solution than that of concrete in the other corrosive solutions. The presence of sulfate ions in composite solutions and in Qinghai salt lake solution reduces the chloride binding capacity of concrete, and it decreases with the increase of sulfate ion content. The chloride binding capacity of plain concrete under Qinghai salt lake solution is about 0.15, and it is 0.13-0.24, 0.25-0.40 and 0.20-0.34 for concrete with fly ash, GGBS and silica fume, respectively. With a fly ash replacement of 20%, GGBS replacement of 35% or silica fume replacement of 8%, the chloride binding capacity of concrete is the highest. The micro-mechanism was also investigated by the thermogravimetric-differential thermal analysis and X-ray diffi-ation techniques.