Testing Research On Green High Strength And High Performance Concrete Made With Recycled Concrete Aggregate

With the development of social economics, the value of concrete is demanded more and more greatly and the resource exhaustion and environment destruction duo to the exploitation sand and stone aggregate has become a focus among people. The conflict between the sustainable development of concrete and the large requirement of aggregate extrudes day by day. At the same time, many old buildings are pulled down for reaching their service life or duo to the urban renewal, which produces a large scale of construction wastes and about 34% waste concrete polluting the environment seriously. If the waste concrete is reclaimed and reused as aggregate to produce recycled aggregate concrete resource as new building materials, the reuse of the waste concrete not only can lower the construction cost, save the natural aggregate resource and alleviate the conflict on aggregate demand and supply, but also can ease the environment pollution, obtaining marked economic benefit, social benefit and environment protection benefit. Therefore, the research on the recycled aggregate concrete has become an important subject in many developed countries and it has obtained a series of important achievement. In our country, the research on the recycled aggregate concrete is also started at present. The recycled is a green concrete, it completely meets the requirement of sustainable development.In this paper, the waste concrete is from a cement concrete road surface in wuhan when it is being rebuilt.Firstly, this paper researches the properties of the recycled aggregate and the aggregate concrete aiming at its shortcomings as lower strength, stronger dry shrinkage, weaker workability and lower durability. Generally examines the physical properties of the recycled coarse aggregate and recycled fine aggregate, compares them with that of the natural aggregate. The result show that the two kinds of aggregates have similar properties and most of the physical properties of the recycled aggregate can satisfy the requirement used for concrete. It also analyses the reasons causing differences between the two kinds of aggregates. By consulting related Japanese Standards and Chinese National Standards, set up the classification system of the recycled aggregate. Investigates the physical and engineering properties, establish two mathematic models that can reflect the mechanical performance of the recycled concrete.Secondly, by initial estimating and later optimizing the proportion, obtains the optimized proportion of the high strength recycled concrete (above C60). This paper compares the recycled concrete at optimized proportion with the routine concrete at thesame proportion in physical properties and mechanical behaviors. We give a quantitative analysis of the crack resistance of the recycled concrete by examining the crack resistance factor. Adopting the routine concrete's producing technologies of high strengthening, compensating contraction and self-compacting, develops the high strength and low brittleness recycled concrete, mini-dry shrinkage and high strength recycled concrete and large fluidity and high strength recycled concrete.Finally, investigates the old cement mortar's activity in recycled concrete, the surface structure of recycled concrete, the interfacial zone between coarse aggregate and cement paste (IZAP) and the action mechanism of super-fine mineral mixture and provides the theoretical basis for further research.The result of this paper show that adopting the technology of mixing with super-fine mineral mixture and high effective water reducer and the technology of pre-wetting the recycled aggregate can make the recycled concrete of high strength and high performance.