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The freeze-thaw cycle damage important influence on the durability of concrete structures, especially in the cold northern regions, almost 100% of the buildings suffered varying degrees of frost damage. Concrete after different freeze-thaw cycles of its internal and external parts of the macroscopic properties and the microscopic structure will change dramatically, therefore, to grasp the damage to the inner and outer parts of the law has a very important significance. This topic using six not blending different w concrete mixing air entraining agent to be tested, the cube specimens used to measure the strength of the 7,14,28,56 d; the prism specimens used for the freeze-thaw cycle test. Measured after different number of freeze-thaw cycles relative dynamic modulus of elasticity, weight loss, and then after the cutting of the specimen do capillary water absorption, the last portion of the sample pressure mercury test obtained a change of pore structure parameters. Eventually come to the inner and outer parts of the concrete in freeze-thaw environments injury law. The test results show that: the strength, the incorporation of air entraining agent, makes air-entrained concrete strength reduced sensitivity to water-cement ratio and strength have different degrees of decline. Frost resistance, entrained concrete with high frost resistance, even if the water-cement ratio of 0.6, the number of freeze-thaw cycles can reach 450 times, and the water-cement ratio is smaller, the better the frost resistance. But ordinary is not doped lead the gas agent frost resistance of the concrete is very poor. The concrete after a certain number of freeze-thaw cycles, the capillary absorption coefficient and the rate of change of water capacity are external significantly greater than the internal, both good correlation. Hole structure, seen by the mercury intrusion test, the incorporation of the air-entraining agent to increase the porosity of the aperture greater than 220nm. Porosity and critical aperture can better be described in the concrete after freeze-thaw cycles of aperture variation, but specific to different parts of the inside and outside of the test piece does not exist a clear distinction. Not doped air-entraining agent of the concrete after a certain number of freeze-thaw cycles, the sound hole, less harmful holes of harmful holes accumulated volume change is small, and more harmful holes increase in the cumulative volume is very obvious, and the water to cement ratio the higher , increasing the sharper. Mixing concrete air-entraining agent after 300 freeze-thaw cycle, harmless hole less harm hole harmful holes cumulative volume change more harm hole cumulative volume increase, but the rate of increase, within 20%. Shows that the air-entrained concrete has good frost resistance.
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