Study On Dynamic Mechanical Properties Of Recycled Aggregate Concrete Under Multiaxial Compressive Stresses

The technology of recycled concrete has realized the reuse of waste concrete,which not only saves resources but also plays a positive role in environmental protection.Concrete in actual structures is mostly in the multiaxial stress state,researches on the mechanical properties of concrete under complex stress state are of great significance to the rational design,safe in operation and save construction materials.Concrete structures are vulnerable to dynamic loads such as earthquake and impact.The study on the mechanical properties of recycled concrete under different strain rates can provide the basis for the seismic design of this kind of structures.This paper mainly studies the following:1.Uniaxial tension and compression tests of five kinds of recycled aggregate concrete under four strain rates were carried out.The experimental phenomena,failure modes,test results and strength of recycled aggregate concrete under uniaxial compression are described and analyzed.The relationship between uniaxial compressive strength and strain rate of recycled aggregate concrete is presented,and the relationship is simplified according to the regular of the parameters in the relationship.The simplified relationship can be used to calculate the dynamic compressive strength of recycled aggregate concrete under different strength grades with the substitution rate of 30%and 50%.Based on the analysis of test data,the uniaxial compressive stress-strain curves of recycled aggregate concrete specimens are presented.2.Biaxial compression tests of five kinds of recycled aggregate concrete under four strain rates were carried out.The experimental phenomena,failure modes,test results and strength of recycled aggregate concrete under biaxial compression are described and analyzed.The effect of strain rate and stress ratio on the biaxial compressive strength of recycled aggregate concrete are studied,and the dynamic biaxial compression failure criterion of recycled aggregate concrete is established.The failure criterion is applicable to the five kinds of recycled aggregate concrete in this test,once the recycled concrete material is given,the failure criterion can be used to calculate the compressive strength of the concrete under arbitrary stress ratio and arbitrary strain rate.Based on the analysis of test data,the biaxial compressive stress-strain curves of recycled aggregate concrete specimens are presented.3.Triaxial compression tests of five kinds of recycled aggregate concrete under four strain rates were carried out.The experimental phenomena,failure modes,test results and strength of recycled aggregate concrete under biaxial compression are described and analyzed.The effect of strain rate and stress ratio on the biaxial compressive strength of recycled aggregate concrete are studied.Based on my tutor's previous research,the parameters of triaxial failure criterion of recycled aggregate concrete under different strain rates are analyzed by regression analysis,and the triaxial failure criterion of recycled aggregate concrete with strain rate parameters is obtained.Based on the analysis of test data,the triaxial compressive stress-strain curves of recycled aggregate concrete specimens are presented.