Experimental Research On Anti—Sulfate Corrosion Fracture Properties Of Concrete Under Wet And Dry Cycles

Sulfate corrosion is one of the important factors that cause the failure of concrete structure, and also is one of the most complicated factors and the greatest harmful of environmental water corrosion. So sulfate corrosion has attracted wide attention. How to prevent and lessen the sulfate corrosion to concrete has become an important content in the study of concrete durability. Hydraulic concrete structures are often in tidal zone, which are under wet and dry cycles and sulfate attack, so that the damage of concrete structure is more serious. Therefore, some tests were carried out to simulate sulfate corrosion and damage process of concrete under wet and dry cycles.7 types of concrete were designed, which corroded by Na2SO4 were examined in this test. The of Na2SO4 is 5%. The compressive strength, splitting tensile strength, mass and three—point bending beams test of concrete were tested in different wet and dry cycles(0, 2, 4, 6, 8,10). In this paper, the macroscopic properties of concrete such as strength and mass varied with sulfate corrosion ages were analyzed. Based on the fracture mechanics, the deterioration regularity of double—K fracture parameters and fracture energy of concrete under different wet dry cycles was studied. The main conclusions are as follows:(1) The compressive strength, splitting tensile strength, double — K fracture parameters and fracture energy of concrete are approximately the same with a two—stage change pattern——increased firstly and decreased with corrosion ages.(2)The addition of fly ash can improve the sulfate resistance of concrete, and the higher content, the better performance of sulfate resistance of concrete.(3)The low content of slag has a detrimental effect on the sulfate resistance of concrete. The compressive strength, splitting tensile strength and double — K fracture parameters of slag concrete are always smaller than that of ordinary concrete and concrete with other admixtures, but the fracture energy is higher than that of ordinary concrete.(4)The compressive strength of silica fume concrete is obviously higher than that of fly ash and slag concrete, but double—K fracture parameters is below the concretewith 20% and 25% fly ash and polyester fiber concrete. the fracture energy is even lower than that of the ordinary concrete. It shows that the effect of silica fume on the fracture performance of concrete is not good.(5)Polyester fiber can significantly improve the concrete resistance to sulfate attack. The compressive strength and splitting tensile strength of polyester fiber concrete are highest. The double — K fracture parameters of polyester fiber concrete is lower than that of concrete with 25% fly ash, while the fracture energy is higher than that of fly ash concrete.