Experimental Study On The Durability Of Concrete Under The Combined Action Of Sulfate Erosion And Freeze-thaw Cycle

There is rich sulfate in water and soil in cold area of north China. When concreteis under the combined action of sulfate erosion and freeze-thaw cycle, it will come upwith more damage than single factor, affect the durability of the structure, and cause alot of loss. It is an important significance in theory and engineering to research thedurability of concrete under the two factor action of the sulfate and freeze-thaw cycle.Experimental study on sulfate-frost of concrete has been carried out. Adopted themethod of fast freeze-thaw test, focused on the effects of the variety of solution、theconcentration of solution and the freezing-thawing cycles, analyzed changing rules ofthe appearance、 microstructure、 mass、 the relative dynamic elastic modulus、compressive strength and depth of damage layers of concrete. Based on themacroscopic damage mechanics theory, damage evolution equations of concrete insulfate-frost cycles had been carried out, discussed the changing rules of damageevolution equations with cycles. The results show that the sulfate solutions have bothinhibitory effect and promoting effect on the freeze-thaw damage of the concrete. Withthe increase of freeze-thaw cycles, the inhibitory effect of freeze-thaw damage for theconcrete with sulfate solution change to be promoting effect. With the increase ofsolution concentration, the promoting effect of freeze-thaw damage for the concretewith sulfate solution change to be inhibitory effect.Experimental study on compressive stress-strain whole curve of the concreteunder water and sulfate frozen has been carried out. Adopted the method of fast freeze-thaw test, got the compressive stress-strain whole curve equation and related parameters. The results show that with the increase of freeze-thaw cycles, thecompression of concrete stress-strain full curves tend to be flatter, peak stress andelastic modulus are gradually declining, peak strain is increasing. The peak stress、elastic modulus and peak strain under water frozen of concrete change faster at first,and under sulfate frozen change faster in the end.