冻融环境下混凝土内外损伤特性的研究

A Study on Characteristics of Internal and External Damage of Concrete Under Freeze-Thaw Environment

混凝土的冻融破坏是当今混凝土耐久性问题的一个重要方面,在混凝土中掺加适量的引气剂能显著提高混凝土的抗冻性,从而增加混凝土的服役寿命。对混凝土不同冻融循环次数后的相对动弹性模量、失重率做了具体分析,并且对试件从外及里各部分进行了毛细吸水试验。结果表明:引气混凝土经过300次冻融循环后仍保持良好的抗冻性,失重率仅为0.3%,普通混凝土的抗冻性较差,100次循环后失重率达到0.9%;未掺加引气剂的混凝土试件经不同冻融循环后外部毛细吸收系数A值均大于其内部的毛细吸收系数,试件内外损伤程度不同。

Freeze-thaw damage of concrete is an important aspect of the concrete durability. Mixing an appropriate amount of air entraining agent can improve the frost resistance of concrete significantly and consequently increase the service life of concrete. In this paper, the relative dynamic elastic modulus and weight loss of the concrete after different freeze-thaw cycles are studied. And capillary suction tests for all specimens from external to internal are carried out. Results show that concrete with addition of air-entraining agent has better frost resistance after 300 freeze-thaw cycles, which weight loss is only 0.3%. Whereas the frost resistance of common concrete is bad, its weight loss is 0.9% after 100 freeze-thaw cycles. The external coefficient of capillary suction is larger than internal＇s after different freeze-thaw cycles no matter the concrete is with addition of air-entraining agent or not. That means the damage degree is different between external surface layer and the internal parts.