Experimental Studyon Basic Mechanical Propertiesof Recycled Concretefor Construction Waste

The construction waste generated by waste concrete and scrapped concrete not only takes up valuable land resources but also causes heavily environmental pollution.The recycling of these construction waste can reduce cost and lower the cost of the whole project,the utilization of resources can also be improved,which will avoid a series of environmental problems.In order to study the mechanical properties of recycled coarse aggregate concrete,the experimental materials selected are as follows: C25 waste concrete of pavement materials,three kinds water-cement ratio designed are 0.47,0.55 and 0.61.The recycled concrete,whose coarse aggregate replacement rates are 0,25%,50 %,75%,100% respectively,go on slump,compressive strength,rebound strength and splitting tensile strength test.According to analysis the experimental results,there are the conclusions:(1)When the water-cement ratio is the same,the slump of recycled concrete decreases with the increase of the coarse aggregate substitution rate.When the substitution rate is 0 to 25%,the 0.47 and 0.55 water-cement ratio Of the concrete slump is decreasing;0.61 water-cement ratio of recycled concrete slump is on the rise.When the replacement rate is between 25% and 100% substitution rate,the slumps of 0.47 and 0.55 water-cement ratios show a steady trend and the 0.63 water-cement ratio slump decreases.(2)When the water-cement ratio is the same,the compressive strength of the recycled concrete increases with the increase of the coarse aggregate substitution rate,and the compressive strength increases first and then decreases.When the replacement rate of coarse aggregate is between 25% and 50%,the compressive strength increases with the increase of water-cement ratio,and the compressive strength decreases with the substitution rate of over 50%.(3)The failure behavior of recycled concrete test pieces is similar to that of ordinary concrete when compressive strength and splitting tensile strength test are carried out.The splitting tensile strength of recycled concrete is lower than that of ordinary concrete,and the splitting tensile strength of recycled concrete decreases with the increase of water-cement ratio.When the substitution rate is 50%,the cleavage tensile strength of 0.55 and 0.61 water-cement ratio is higher than that of other substitution rates.(4)The ratio of splitting tensile strength and compressive strength of the three water-cement ratios is close to 0.093.With the increase of the aggregate substitution rate,the ratio of splitting tensile strength and compressive strength is basically stable near 0.09 trend.The rebound strength of recycled concrete with the same water-cement ratio is lower than that of ordinary concrete.With the increase of compressive strength of recycled concrete,the rebound strength increases,and there is a good positive correlation between them.This is basically consistent with ordinary concrete.Through different experiments,we can find that as long as the mix proportion design is reasonable,the performances of recycled concrete and ordinary concrete are not big difference,and can meet the requirements in the application of engineering practice,which will be better applied to the engineering structure to provide theoretical guidance in the further development of recycled concrete.