Experimental Study On The Effect Of Recycled Coarse Aggregate On The Mechanical Properties Of Recycled Concrete

With the rapid development of urbanization in China,the demand for resources and the discharge of construction waste are increasing day by day,resulting in the shortage of construction material resources and a large number of environmental pollution problems of construction waste.Recycled concrete technology perfectly solves those two problems.It realizes the recycling of building concrete materials,and thus brings remarkable economic and environmental benefits.However,due to the influence of the performance defects of recycled aggregate,the basic mechanical properties of recycled concrete are lower than that of natural concrete,which limits its application in engineering.Therefore,further research on recycled concrete is needed.Based on the mix ratio of C30 concrete used in practical engineering,natural coarse aggregate is replaced by recycled coarse aggregate in the proportion of 10%,20%,30%,40%,60%,80% and 100% to prepare recycled concrete.The influence of recycled aggregate content with different replacement ratio on the mechanical properties of recycled concrete is studied through experiments,and then the recycled aggregate mixing is analyzed through fatigue test results.The fatigue life,fatigue probability distribution and damage evolution of concrete are studied.This experiment and main research work are as follows:(1)The apparent density,water absorption,crushing index and mortar content of recycled aggregate were measured,and compared with natural aggregate,the defects of recycled aggregate were analyzed.(2)Forty-eight standard cubic specimens of 150 mm * 150 mm * 150 mm * 150 mm were fabricated for cubic compressive test and splitting tensile test,respectively.The effects of mass substitution fraction of recycled aggregate on compressive and splitting tensile properties of recycled concrete were compared,and the failure process and morphology of the specimens in the test were observed.(3)Ninety-six standard trabecular specimens of 150 mm* 150 mm *550 mm were fabricated,of which 24 were used for static four-point bending test to study the effect of mass substitution fraction of recycled aggregate on the flexural properties of recycled concrete.(4)The fatigue life of recycled concrete is obtained by fatigue test of the remaining 72 beams under three stress levels,and the strain-fatigue curve is drawn.The fatigue life of recycled concrete is analyzed with Weibull distribution data,its double logarithmic fatigue equation is derived,the fatigue ultimate strength is obtained,and the fatigue damage mechanism is analyzed.