Research On The Deterioration And Damage Of Concrete Under Sulfate Attack And Freeze-thaw Action Coupling

Soil contains large amounts of sulfates in northern China, concrete structures subjected to sulfate attack is widespread, and in cold areas concrete structures often suffer from freeze-thaw damage. Under sulfate attack and freeze-thaw cycles coupling action of concrete, and due to interaction of two factors, will produce more severe damage. Considering the complexity the environment in which the concrete, conducted the damage of concrete under sulfate attack and freeze-thaw cycles coupling action to provide guidance and advice for the development of concreteTest analysis of the deterioration law of concrete under sulfate and freeze-thaw action coupling, select the levels and factors of concrete damage, 1.e. Na2SO4 concentration(0%、5%、10%), fly ash(10%、 15%、25%), silica fume(5%、8%、11%), gas content(3.5%、5%、7%), water-cement ratio(0.38、0.33), analysis of diffeent factors on damage of concrete under sulfate attack and freeze-thaw cycles coupling action, combining microcosmic study to further explore the damage mechanism of concrete. The main contents and results are as follows:(1) Different ratios with concrete specimens conduct 28d compressive strength test. The results show that the same water-cement ratio, fly ash incorporation reduce 28d compressive strength of concrete; large amount of silica fume can improve 28d compressive strength of concrete; entraining agent incorporation significantly lower 28d compressive strength of concrete.(2) The results of wet-dry cycle test show that fly ash and silica fume can improve the sulfate attack resistance to concrete; the ability to reduce the sulfate attack resistance to concrete air-entraining; the smaller water-cement ratio, the better the sulfate attack resistance to concrete.(3) Research on the different ratios with concrete specimens resistance to salt freezing in the water and 5%,10% Na2SO4 solution by using fast-freezing method. The results show that different concentrations of sodium sulfate caused by the degree of damage of concrete varies; incorporation of an appropriate amount of fly ash, silica fume, air-entraining agent may improve the concrete resistance to salt freezing; The smaller the water-cement ratio, the better salt freezing resistance of concrete.(4) By SEM analysis, the sodium sulfate attack product growth changes.