The Influence Of Air Entraining And Hydrophobic Components On The Permeability And Frost Resistance Of Concrete

Freezing thawing damage is one of the most common failure phenomena of concrete, especially in the freezing and thawing regions. Under the separate or combined effect of air entraining agent and waterproofing agent, the frost-resisting and anti-permeability of concrete can be greatly improved. Most of the scholars at home and abroad have studied is the effect of air entraining agent or waterproofing agent alone. Therefore, this paper aims to study the synthetic effect of the air entraining agent and waterproofing agent. Choosing the typical concrete mix ratio, using electric flux method and the superficial gas permeameter analyzes its anti permeability, and using the rapid freezing and thawing test evaluates its frost resistance. At last, the bubble parameters, pore structure, pore size distribution and the structure of interface transition zone of hardened concrete are analyzed.Firstly, the influence of air entraining agent on frost resistance and impermeability performance under the steam curing and normal temperature curing.are analyzed. The results show as follows: whether steam curing or curing at normal temperature, the frost resistance and permeability of concrete with larger amount of air entraining agent is better, but its initial strength is relatively low. As for the micro perspective, in the premise of the same amount of air entraining agent, the spacing coefficient of autoclaved concrete is greater than normal temperature curing concrete’s, but its most probable pore diameter is less than the normal temperature curing concrete’s, and autoclaved concrete contains more larger pores(>1000nm) and smaller pores(<10nm), but normal temperature curing concrete contains more pores(10nm~100nm) which are favorable to the frost resistance and impermeability performance.The crystal content in the interfacial transition zone for autoclaved concrete is relatively higher, small cracks exsites in its interface zone or paste without the freeze-thaw cycles, in terms of autoclaved concrete, freeze-thaw damage can occur in the interface transition zone and paste parts at the same time, but the damage of normal temperature curing concrete is mainly concentrated in the interfacial transition zone.Secondly, this paper studies the comprehensive effects of air entrained and waterproof agent on concrete under normal temperature curing system. The results show that: the use of the air entraining agent and water repellent agent can make the strength of concrete decrease, but the frost resistance and impermeability performance of concrete is obviously improved. Organosilicon waterproofing agent and air-entraining agent can significantly improve the resistance performance of water and chloride ion penetration, and infiltration crystalline waterproofing agent can comprehensively improve the permeability resistance of concrete, after 200 times freezing and thawing cycles, the use of infiltration crystalline waterproofing agent make the surface gas penetration depth of concrete with the same gas volume decrease by 19.18% at most, and its permeability products mainly contain ettringite(Aft), calcium hydroxide(CH), calcium silicate hydrate(C-S-H) and calcium carbonate(Ca CO3), and its penetration depth in concrete can be up to 8~12mm. The use of waterproofing agent make the bubble spacing coefficient have a tendency to decreasing, and the bubble spacing coefficient of concrete with the most excellent frost resistance and anti permeability performance is only about 138μm, 257μm lower than the blank concrete. The use of waterproofing agent make the pores(10~100nm) ratio of concrete increase, and make the most probable aperture of concrete have a tendency to decreasing, and make the structure of interface and slurry more uniform, continuous, dense, the function of infiltration crystalline waterproofing agent is the most obvious among them.In the end, this experiment dentifies the best composition of concrete admixture is: 1.5? air-entraining agent +1.0% organosilicon waterproofing agent+ outside with 0.8~1.0mm infiltration crystalline waterproofing agent. After 300 freezing and thawing cycles, the mass loss of concrete with the best admixture composition is only 0.81%, and the antifreeze level of concrete with the best admixture composition achieve DF300.