Study On The Influence Of Freeze-thaw Cycle And Sulfate Erosion On The Mechanical Properties Of Concrete

The climatic conditions of high and cold and the natural geographical conditions of a large number of salt lakes in western China will have a great impact on the performance of concrete structures in many water conservancy projects in western China.The results show that freeze-thaw and sulfate erosion are important factors affecting the mechanical properties of concrete,and the change of mechanical properties of concrete is directly related to the safety and performance of concrete structures.Therefore,it is necessary to study the mechanical properties of concrete under freeze-thaw cycle and sulfate erosion.In this paper,under the action of single freeze-thaw cycle,single sulfate erosion,sulfate erosion and freeze-thaw cycle alternately,concrete specimens are subjected to different cycles of action and different confining pressures.The effects of single external environmental factors and double external environmental factors on the mechanical properties of concrete under triaxial compression were studied under different loading rates.The results show that:(1)the axial compression strength of concrete specimens under uniaxial and three axis compression decreases with the increase of single freezing and thawing cycles and the number of alternate cycles,and the axial compression of concrete specimens under uniaxial and three axis compression increases with the increase of single and three shaft drying cycles.The strength increases first and then decreases gradually,but the compressive strength of the concrete under the effect of different factors is less than that under the action of the single axis under the effect of three axis.(2)under the action of single freezing and thawing cycle and single sulfate dry and wet cycle,the axial peak strain of concrete increases with the increase of the number of cycles.Under the same freezing and thawing cycle,the strain growth rate of concrete under the action of three axis is greater than that under uniaxial action.Under the action of the same dry and wet cycle,the strain growth rate of concrete under the action of three axis is less than the strain growth rate under the action of single axis.(3)With the increase of confining pressure,the increase of axial compressive strength and the increase of axial peak strain of concrete with more damage degree under the action of different environmental factors.(4)the axial compressive strength of the concrete specimens with different damage degree increases with the increase of the strain rate,and the increase of the axial compressive strength decreases with the increase of the strain rate,and the axial peak strain decreases with the increase of the strain rate,and the reduction amplitude under the compression of the three axis is less than that under the single axis.But the axial compressive strength growth rate and the axial peak strain growth rate are not significantly related to the damage degree of concrete.The research results in this paper can provide some theoretical basis for the design of concrete structure in freeze-thaw cycle and sulfate erosion environment,and have good reference value for the study of similar problems.