Experimental Study On The Mechanical Properties And Mixed Proportion Of Full Recycled Aggregate Concrete

Construction waste is a major component of municipal solid waste,according to statistics,the building demolition and construction waste volume of most countris in the world is about 30%to 40%of that of total municipal solid waste.The composition of construction waste is complex,with a high proportion of 30.7%broken bricks and 38.3%concrete blocks of brick and concrete structure building,which can be processed into recycled aggregate as renewable resources,it will not only solve the problem of high consumption of natural aggregate resources,protect the ecological environment of aggregate origin,but also settle disputes of urban waste pile,area and environmental pollution,achieve recycling materials during the process of concrete production,ensure the sustainable development of the construction industry.In this paper,the waste brick of brick and concrete structure,unknown strength concrete test blocks in laboratory were crushed and screened as recycled coarse aggregate,fine aggregate for physical performance test.Made concrete with 100%replacement of natural gravel by waste brick coarse aggregate and with 100%replacement of natural sand by crushed concrete fine aggregate.The results provided reference and research basis for the research of recycled concrete wall.Main researches were as follows.Made research on physical properties of recycled coarse and fine aggregate,test results showed that the size and gradation of which does not met the requirements of relevant standards.The apparent density,packing density reduced to a certain extent than that of natural aggregate and the porosity increased,the water absorption of waste brick coarse aggregate was much higher than that of natural gravel.Made experimental study on compressive strength,axial compressive strength,elastic modulus of recycled concrete,the results showed that the growth pattern of strength of early age recycled concrete was similar to ordinary concrete,the 28d strength of recycled concrete with high water-cement ratio met the code requirements.The relationship between the standard value fck of axial compressive strength and the standard value fcu,k of the cube compressive strength in Specification for concrete was suitable to recycled concrete in this article.The modulus of elasticity of recycled concrete was respectively 35%to 44%and 22%to 31%lower than that of ordinary concrete and waste concrete recycled aggregate concrete which with a equivalent strength.The article suggested the formula between the modulus of elasticity of recycled concrete and compressive strength.Made research on shrinkage and carbonation resistance of recycled concrete,test results showed that the shrinkage of recycled concrete was higher than that of natural aggregate concrete,40%to 49%lower than that of the waste concrete recycled aggregate concrete of 28d,the carbonation depth of the early age recycled concrete was 20%to 44%larger than ordinary concrete.It was recommended the basic formula of shrinkage and the model of carbonation depth of early age recycled concrete.Made quantitative analysis of the economy of recycled concrete,the results showed that with considering the construction waste disposal fee,the cost of recycled aggregate concrete in this paper,with mix ratio of RA,RC was respectively 27.9 yuan/m3,40.6 yuan/m3 lower than natural concrete with grade of C15,C20.The recommended mix ratio of recycled concrete with grade of C15,C20 was RA,RC.