关键词: 混凝土;含气量;抗压强度;抗氯离子渗透性;微观结构

Abstract: By experiment, the gradual-loss law and influencing factors of the air content of concrete and the effects of curing temperature and air entraining agent on concrete compressive strength, chloride ion permeability and micro pore structure were studied.Results show:The air content of fresh concrete is related to the initial gas content of concrete, the greater initial gas content, the greater loss.In the dynamic process, the fresh concrete containing gas loss is greater than the static process.Compared with standard curing condition, the negative temperature curing on the one hand makes hydration reaction of concrete more slowly and hydration degree lower, on the other hand, water turns into ice can also cause the expansion of the volume, destroy the inside crystal structure of concrete and damage the internal pore structure of concrete (the damage is not recoverable to a certain extent), this is why the compressive strength of concrete decreases, the chloride ion permeability and the bubble spacing factor increase.Air entraining agent can introduce a large amount of tiny bubbles, as a result, the pore content of small aperture in concrete will increase.To a certain extent, air entraining agent improves the connectivity of pores, reduces the relative stress area of concrete, thereby, the compressive strength of concrete decreases, the electric flux increases and the pore size distribution will shift towards the direction of small aperture.

Key words: concrete;air content;compressive strength;chloride ion penetration;microscopic structure