Abstract:

The salt frost resistance,as well as the relationship between the salt frost resistance and the air bubble parameters,is investigated by means of the accelerated freeze-thaw method for common concrete,air-entrained concrete and high-performance concrete under the action of 3.5%（mass fraction） sodium chloride solution,respectively.The results show that the average spacing factor（） and bubble diameter（） of concrete is largely dependent on air content in a negative relation when the air-entraining agent is determined,that mineral admixture has no significant influence on the bubble characteristics of concrete and its regularity,that adding air-entraining agent is an effective means of improving the anti-freeze-thaw performance of concrete,and that there also exists a critical air content of concrete the same as common freeze-thaw performance,which is 2.0%～3.0% in common freeze-thaw environment and rises to 4.5%～5.0% in salt freezing environment.Moreover,it is found that the average spacing suitable for the salt frost resistance of high-performance concrete is related to the strength grade of concrete,and should be less than 250 μm when the strength grade of concrete is less than C50.Meanwhile,it can rise to 700 μm when the strength grade is greater than C60.

Key words: high-performance concrete, air-entraining agent, air-entrained concrete, frost resistance, air bubble, structural characteristic, freeze-thaw cycle