对混凝土耐久性问题的新认识

A New Viewpoint of Concrete Durability

摘要:

论述了混凝土渗透性与耐久性，引气与耐久性的关系,探讨了引气改善混凝土耐久性的作用机理。混凝土渗透性与Cl-离子侵入、碳化、硫酸盐化学侵蚀有一定相关性。渗透性与其它一些耐久性如抗冻性、硫酸盐结晶破坏、碱集料反应等关系不大。在保证混凝土具有一定强度的前提下，引气可显著改善混凝土综合耐久性能。在同强度条件下，引气可改善混凝土的抗渗性能，对提高抗Cl－离子侵入、硫酸盐化学侵蚀、碳化等化学侵蚀引起的破坏有利；引气还可显著改善抗冻、碱集料反应和盐结晶等因膨胀引起的破坏。

关键词:混凝土;耐久性;引气;抗冻性;抗渗性

Abstract:

The relationship between permeability and durability, effect of air entrainment on durability of concrete and the improvement mechanism of concrete durability by air-entrainment were investigated in this paper. There is relationship between permeability and some durability caused by chemical attacks such as chlorine ion intrusion, carbonation and sulfate chemical erosion. There is no definite connection between permeability and the durability caused by expansion such as freeze resistance, sulfate crystallization and alkali aggregate reaction. When the concrete has an appropriate strength, the resistance of concrete to attacks can be improved because air entrainment can decrease permeability of concrete and air bubbles act as a lot of compression release value to reduce the pressure produced by expansion. Not only the damage caused by chemical attack can be reduced, but also the damage caused by expansion can be reduced significantly. In addition, the early cracking of concrete can also be modified drastically. Therefore, the comprehensive durability can be improved by air entrainment in comparison with the ordinary concrete at equal compressive strength.

Key words:concrete; durability; air-entrainment; freeze resistance; permeability