Experimental Study On The Long-term Properties And Mixed Proportion Of Full Recycled Aggregate Concrete

With the further development of new countryside construction and urbanization, construction waste emissions are increasing year after year in China. However, most of the construction waste without any treatment, were transported to the countryside or city perimeter with simple landfill or open-air piling up, which not only wastes land and resources, but also pollutes the environment; In addition, in the process of new countryside construction and city transformation, the demand of natural sand gravel is growing, and long-term mining is very easy to bring about the exhaustion of resources, even the destruction of ecological environment. So production and use of recycled aggregate has important significance of conserving resources, protecting environment and realizing the sustainable development of the construction industry.In order to research and product vibrational wallboard of recycled aggregate concrete, and to get it more extensive application in practical engineering of the new countryside construction, In this paper, the waste brick of brick and concrete structure, unknown strength concrete test blocks in laboratory are crushed and screened as recycled coarse aggregate, fine aggregate. Five group concrete of different proportion with100%replacement of natural gravel by waste brick coarse aggregate and with100%replacement of natural sand by crushed concrete fine aggregate are made by us. In this paper, main researches are as follows.(1) Some physical properties such as the size and gradation, the apparent density, the packing density, the porosity, the water absorption and the water ratio of recycled coarse and fine aggregate are researched and analyzed. Compared with natural aggregate, the apparent density and the packing density of recycled aggregate reduce to a certain extent, the porosity and the water absorption are greatly improved.(2) Some mechanical properties such as long-term compressive strength, axial compressive strength of28d and elastic modulus of recycled concrete are studied and discussed. The growth pattern of strength and the destructive form of recycled concrete are similar to ordinary concrete, compressive strength increase with the increase of its age, but its change is not obvious with the change of water-cement ratio, so it can save economic cost if we make recycled concrete with high water-cement ratio in practical engineering. 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 is suitable to recycled concrete in this article. The elastic modulus of recycled concrete is lower than ordinary concrete and waste concrete recycled aggregate concrete which with an equivalent strength.(3) Based on shrinkage and carbonization test of recycled concrete, the changes of shrinkage and carbonation depth under the age of3d,7d,28d60d,90d,120d and180d are analyzed. The models of long-term shrinkage and carbonization depth of recycled concrete are given in this paper.(4) Economic benefits of recycled concrete are analyzed. Recycled concrete of C15, C20are respectively25.9yuan/m3,38.6yuan/m3lower than natural concrete which with an equivalent strength. In addition, by using recycled concrete, much money in the process of managing construction waste can be saved. It has good economic benefits and social benefits.