氯化钠、硫酸钠溶液对混凝土抗冻性的影响及其机理

研究了混凝土在质量分数为3．5％的氯化钠溶液、5．0％的硫酸钠溶液中的抗冻性，结果表明，不同的盐溶液对混凝土抗冻性有不同的影响，在氯化钠溶液中冻融时，混凝土表面产生严重的剥落；而在硫酸钠溶液中冻融时，质量损失小，原因在于氯化钠溶液冻结以后压缩塑尾较小，而硫酸钠溶液冻结后在压缩塑性很大，在溶液中冻融时混凝土的相对动弹性模量下降比在水中略为缓慢，但水灰比0．26的混凝土在硫酸钠溶液中冻融后期相对动弹性模量下降很快，过早破坏，原因在于经过一定时间硫酸盐侵蚀发挥作用以后与冻融破坏产生交互作用。

EFFECI OF NaCI AND Na2SO4 SOLUTION ON THE FROST RESISTANCE OF CONCRETE AND ITS MECHANISM

The frost resistance of non air_entrained plain concretes with water/cement ratios of 0.44, 0.32 and 0.26 subjected to the action of 3.5% (in mass) sodium chloride (NaCl) solution or 5.0% (in mass) sodium sulfate (Na 2SO 4) solution was investigated. The results show that the frost resistance of the concretes is influenced by the type of salts used. When the concretes subjected to freezing and thawing in Na 2SO 4 solution, the surface scaling of concrete, as seen in NaCl solution, is unnoticeable. The principal reason may be attributed to the fact that the ductility of ice sample made by frozen Na 2SO 4 solution is greater than that of frozen NaCl solution. For concretes with water cement ratios of 0.44 and 0.32 subjected to freezing and thawing in the salt solutions, the decrease of relative dynamic modulus of elasticity is slightly slower than that in pure water. However, for concrete with water cement ratio of 0.26 subjected to freezing and thawing in Na 2SO 4 solution, the decrease of relative dynamic modulus of elasticity is accelerated at the late stage of the damage process, which may be due to the interaction of sulfate attack and freeze-thaw cycling.