Study On Damage Properties Of High Strength Concrete Under Combined Action Of Loading History And Environmental Factors

High-strength concrete are suffered from varying degrees of damage for a long time,due to improper construction,natural disasters,accidental load and other reasons in the process of using,and the structure will be in the corrosion conditions of chemical medium,atmosphere of CO2 and others,therefore,the durability and mechanical properties of the structure will be deteriorated.So it is important to study on damage properties of high-strength concrete under combined action of loading history and environmental factors.The major work of this paper is as follows:(1)The sulfate attack tests subjected to conditions of long-term immersion and dry-wet cycle are conducted on high-strength concrete specimens with different axial compression load histories,which the size of specimens is 100mm×100mm×300mm.In addition,the uniaxial compression tests are carried out after erosion of 180 d.The impacts of loading history,sulfate concentrations,erosion time,erosion conditions on the quality change,peak stress,peak strain,elastic modulus,stress-strain curve are analysed.The test result showed that: with the increase of the concentration of sulfate solution,the peak strain of high-strength concrete is decreased firstly and then increased subjected to the condition of long-term immersion,while peak strain is increased under dry-wet cycle condition.The trend of peak stress and elastic modulus with the increase of the solution concentration,are dropping after increasing firstly in the condition of long-term immersion,but they are declined sustained subjected to dry-wet cycle.Under the two conditions,with the increase of historical load,the peak stress decreases,the peak strain increases,the elastic modulus decreases,but the change is smaller.(2)The coupling effect of fatigue load and carbonation environment was studied to the high-strength concrete specimens,which the size is 100mm×100mm×300mm.The influence of different fatigue historical load and carbonation time on the carbonation depth,peak stress,peak strain,elastic modulus,stress-strain curve are studied.The analysis results showed that: with the increase of the carbonization time,the carbonation depth,the elastic modulus,and the peak stress increase gradually,and the larger of the fatigue load is,the larger of the peak stress increases with the carbonation time,but the peak strain is reduced,and its change is not obvious.Subjected to single fatigue history load,the peak stress decreases and the peak strain increases,with the increase of fatigue loading history,but as the increase of the carbonization time,this trend is gradually shrinking smal.(3)The damage characteristics of historical load and environmental factors were studied by presenting the proposed joint factor K and the ductile damage factor ?D,it is indicated that the combined effect of the historical load damage and sulfate attack,carbonation erosion have a promoting effect on high-strength concrete.In general,the combined effects of acceleration of ductile damage will be more obvious,when the carbonization time and the fatigue history load are larger.