Experimental Study On Behavior Of Recycled Concrete Under Combined Compressive And Shearing Stresses

This work is a subtopic of the project " Experiment study and design method tocomposite mechanical behavior of recycled concrete members and mechanicalproperties of recycled concrete in the freeze-thaw environment "(Grant No.51278151), supported by the National Natural Science Fundation.Dealing with the waste concrete into recycled aggregate for preparing recycledconcrete can alleviate the pressure of the natural aggregate resources, reduce thepollution of the environment and creat good social and economic efficiency. Inconcrete structure of practical engineering, concrete is often in complex stress staterather than in uniaxial tensile or compression stress state. So the research of failurecriterion for recycled aggregate concrete under complex stress state is of greatsignificance.Based on the cross section of concrete structural components subjected to thecombined actions of compressive and shearing stresses, the compression-shearcorrelation studies under the complex stress state of recycled aggregate concretewere investigated in this paper. A total of75hollow cylinder specimens prepared byrecycled aggregate concrete with recycled coarse aggregates replacement ratio of0%,30%,50%,70%and100%were examined under pure shear and combinedcompression and shear stresses by self-designed loading device. Based on theexisting strength rule of the concrete, their corresponding expressio ns undercombined compressive and shearing stresses were obtained by transformationformula.Tests showed that the introduction of recycled aggregate reduced the shearstrength of the concrete in the state of pure shearing stress. The failure modes andthe changing laws of the shear stress-strain relation were similar for the specimenswith different recycled coarse aggregate replacement ratios under different axialcompressive stress ratio. The ultimate shear stress improved with the increasingaxial compressive stress ratio when it below0.6and declined after more than0.6.The testing results were compared and analyzed by applying multiple strengthcriteria and the failure criterion curve equation for recycled aggregate concreteunder combined compression and shear stresses was established with octahedralstress theory parabolic fitting formula.The biaxial tension-compression strength of specimens in principle stress spacewere obtained by converting the failure strength under combined compression andshear stresses. The shear strength of28recycled concrete beams without stirrupswere calculated with the suggested failure criterion curve equation and the equationof the shear bearing capacity of oblique section for eccentrically compressed members also was discussed, verifying the validity and practicability of the failurecriteria which providing references for working out <Technical code on the structureof recycled concrete>(serial No. HB130928002).