Research methods: First, the base test is done from beginning with analysis of the concrete freeze-thawing mechanism, then the researches are done on the influence on the concrete durability by the sir content through adjustments of air entrainment, ratio of water and glue, sand ratio, mixture ratio of fly-ash, coarse aggregate grading, fine aggregate modules, mixture temperature of concrete, static time and the other factors.
Research conclusions: The air content of concrete increases with increment of air entrainment and the air content of concrete reduces with reduction of the ratio of water and fly-ash. The air content of concrete reduces seriously with increments of sand ratio, air content and mixture ratio of fly-ash. The air content reduces with increment of grain size of stone and the air content of concrete mixed with single particle grade is less than that of the concrete mixed with continuous grading aggregate. The air content of concrete mixed with medium-sized sand is high and stable and to this concrete, the tamping time is longer and the lie of air content is more，but ff the tamping time is short, the quantity of air entrainment is not enough and if too long, the sir bubble will lose. The strength of concrete will reduce with increment of air content, so durability. national selection of sir content of concrete is the key point of guaranteeing concrete
2007, Vol. 24 
