Mechanical Property Of Recycled Coarse Aggregate Concrete And Precasted Wall Slab Members Made With Construction Waste Of Clay Brick

China is still in the period of large-scale capital construction, new construction and demolition of old buildings have generated a lot of construction waste. However, most of the construction waste is transported directly to the countryside or city perimeter with simple landfill or open-air piling up without any treatment, which not only wastes arable land and natural resources, but also pollutes the environment. In China, a lot of old buildings in urban and rural areas is masonry structures or hybrid structure, and waste clay brick account for a large percentage in all construction waste, on which few studies have been carried out.This paper aimed at the urgent problem of waste brick recycling, carry out the research on recycled waste clay brick coarse aggregate concrete and mechanical performance of recycled precasted wall slab, strive to develop a new type of wall materials with waste clay brick. Research content of this paper is important for the promotion of construction waste utilization, resource conservation and environment protection. The research result can provide engineering application reference of recycled waste clay brick coarse aggregate concrete precasted wall slab. This work was funded by the New Wall Materials Reform Fund of Henan Province.On the basis of test research on physical and mechanical properties of recycled wasted clay brick coarse aggregate and recycled construction waste fine aggregate, mixture test research on recycled waste clay brick concrete is carried out. The recycled concrete precasted wall slab is made of large size recycled wasted clay brick coarse aggregate and recycled construction waste fine aggregate. Mechanical performance experiment and numerical analysis of such new wall slab under vertical load, out-of-plane load and low cyclic loads with given axial compression ratio is carried out. Proposal for engineering applications is put forward according to the research result and relevant reference. The main work and research result of the paper is as follows.1. Systematic testing and analysis on physical and mechanical properties such as particle size distribution, apparent density, bulk density, porosity, water absorption and crushed indicators of crushed large size waste clay brick coarse aggregate and crushed concrete fine aggregate is carried out and compared with the natural aggregate. Test result show that recycled waste brick coarse aggregate is characterized with low strength and only suitable for the wall slab members and others that have a low demand on strength. Except has a higher water absorption, recycled waste concrete fine aggregate is similar to natural sands and can be used instead of natural sands in concrete mixture after certain treatment.2. Recycled concrete mixture were designed with 100% recycled large size waste clay brick coarse aggregate and 100% recycled waste concrete fine aggregate. According to the high water absorption characteristic of recycled waste clay brick coarse aggregate, methods as additional water added in advance and two-stage mixing procedure is employed to improve the working performance of concrete mixture. The strength level of recycled concrete can reach C10-C20. Based on the experiments result, relationship between cubic strength and net water to blinder ratio was obtained.Test research on compressive strength, elastic modulus, shrinkage deformation, carbonation performance and etc. of recycled waste clay brick coarse aggregate concrete is carried out. The formula of modulus elasticity and recommended indicators of mechanical properties is proposed, which provide reference for wall slab analysis and engineering application.3. Precasted wall slab with normal concrete as edge member and large size recycled wasted clay brick coarse concrete as the core part is made, and experiment research of wall slab under vertical load and out-of-plane load is carried out.Test result shows that under vertical in-plane load, normal concrete of edge member can together with the core recycled concrete, and both can exert strength better. Design equation was advised for the recycled wall slab under in-plane vertical load, which have a large safety reserves and assure no crack appeared under normal service limit state. Under uniform out-of-plane load that higher than wind load, lateral deflection is very small and no crack appeared.Based on elastic thin plate theory and elastic support boundary conditions, the equation for displacement, internal force, stress and strain of recycled wall slab under uniform out-of-plane load Is derived, which provide effective methods for stress analysis of wall slab under out-of-plane load.4. Mechanical performance experiment of recycled concrete precasted wall slab under low cyclic loads with given axial compression ratio is carried out. The energy dissipation, deformation capacity, hysteretic behavior, ductility and rigidity degeneration and failure mechanism of recycled concrete precasted wall slab before and after cracks appeared were analyzed.Test result shows that the stiffness degradation of recycled concrete precasted wall slab before cracking is not obvious and horizontal loads keep stable. The energy dissipation and deformation capacity of recycled concrete precasted wall slab is better after cracking.Refered to the shear bearing capacity calculation method of deep flexural members, the shear bearing capacity formula of recycled concrete precastesd wall slab that consider the effect of edge column concrete is established. According to the formula, the calculation result fitted well with test results and thus can be refered by engineering design.5. According to materials properties test result of recycled waste clay brick coarse aggregate concrete, finite element software ABAQUS is used to establish the analysis model of recycled concrete precasted wall slab. Numerical analyis on mechanical performance of recycled concrete precasted wall slab under low cyclic loads is carried out and comparied with the experiment result.The comparision result shows that the stress state, energy dissipation, deformation capacity, hysteretic behavior, skeleton curve, ductility and rigidity degeneration and residus deformation by numerical analysis under each load cycle is very closer to the experiment result. The finite element analysis considering materials properties of recycled waste clay brick coarse aggregate concrete may be a efficient method to analysis the mechanical performance of recycled waste clay brick coarse aggregate concrete precasted wall slab.6. According to experiment research result and relevant reference, the preliminary proposals of recycled concrete precasted wall slab applied on storey bearing wall and frame building facades and wall, including production of recycled concrete precasted wall slab, main points of design and constrcution is suggested.Combined with the status and problems of China’s recycling of construction waste, proposals to promote the industrialization of waste disposal and engineering application of recycled concrete precasted wall slab is presented.