Mechanical response and microstructure difference analysis of concrete subjected to strong acid under multistage cyclic loading
The strength det erioration and acoustic emission characteristics of natural and strong acid concrete under multi-stage cyclic loading are very important for the stability evaluation of concrete structure.Through the multi-stage cyclic loading test of natural and strong acid concrete,the strength deterioration characteristics of natural and strong acid concrete under uniaxial linear loading and graded cyclic loading and unloading and the acoustic emission concentration trend characteristics of each grade are explored.The results show that the strength of concrete under uniaxial multi-stage cyclic loading decreases obviously,which shows that both strong acid and multi-stage cyclic loading stress path have degradation effect on the strength of concrete,and the multi-stage cyclic loading stress path has more obvious effect on the strength reduction than strong acid.Under uniaxial multi-stage cyclic loading,the acoustic emission events of concrete mainly appear in the loading stage,and the maximum value appears in the middle of each cycle or near the peak value,while there are only a few acoustic emission events in the unloading stage.Except for the last stage loading to the failure stage,the acoustic emission signals of concrete under strong acid action in each stage loading are less severe than those of natural concrete,which shows that the acoustic emission signals of concrete under strong acid action in each stage loading are slightly higher than those of natural concrete.The internal pores and fissures of the concrete are well developed,with clusters and circles as the main pores,dense areas with massive pores and irregular fissures.The internal layered structure of the concrete is obvious,and the layered structure and pore fissures are alternately distributed in the concrete.The research results can provide scientific basis for stability evaluation of concrete structures under disturbance.
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