The Application And Fundamental Performance Of Recycled Aggregate Concrete On Wenchuan Seismic Area

This dissertation was funded jointly by two projects, which are the project of national science and technology supporting plan (2009AA032304) and the key project of the Science and Technology Department in Sichuan province (2009GZ0043). A huge number of building wastes need to be disposed in the process of urban construction and after the serious natural disasters like the Wenchuan earthquake. Thus, it has significant impact in economics and ecology to dispose a vast quantity of construction waste properly, to recycle all kinds of building materials as much as possible, and to reduce the damage to the environment furthest. And all these have the guiding and demonstration effect. As far as the waste concrete, after recycling, cleaning and sorting, it can be crushed into pieces and used in the production of various types of recycled aggregate concrete products, which is an effective technical approach in eliminating the construction waste and re-utilizing the resources. However, the properties of these products are not that stable on account of the effect of the producing area, original strength, age and producing condition. At the same time, for the situation that a set of practical production technique is needed urgently in disposing the construction waste and producing all kinds of building materials in the process of post-disaster reconstruction in Sichuan, based on a lot of experimental studies, this dissertation focused on the application conditions of renewable concrete aggregate, and it studied three aspects, namely the essential performance measurement, theory and method of designing, and the development and application of new products.1. For the issue that the differences between recycled aggregates are big, the fundamental physical properties, including absorption rate, moisture content, apparent density and bulk density were measured in this dissertation. Then, the effects of aggregate size, graduation and The original concrete strength on properties of aggregate were discussed. As for the experiment, the method of orthogonal test was used to design mixture ratio for C30regenerated concrete. After analyzing the influence of grain composition, admixture and cement ration to the workability and strength of the concrete, the benchmark proportion for regenerated concrete was set finally. Through comparison tests, the compression strength of regenerated concrete aged3d to28d with50%,70%and100%substitution rate are measured, and the strength equation of regenerated concrete with different ages and substitution rates were deduced. Meanwhile, the non-destructive strength tests were conducted on78sets of test specimens with rebound method and ultrasound rebound method respectively. And then after contrasting the strength-measuring curve of ordinary concrete, the correction advices were presented.2. According to the requirement of wall materials in reconstruction after earthquake in Sichuan area, production technique was developed to process the recycled aggregate into insulation hollow blocks. In this dissertation, through the methods of theoretical analysis and finite element analysis, considering the demand of heat insulation and bearing, the aperture-opening method of cavity blocks has been optimized, thus not only meet the national criteria for wall’s energy conservation, but also have relatively high bearing capacity. At the same time, after horizontal low cyclic loading tests on four non-reinforcing wall pieces, properties of shear resistant strength, fracture morphology, hysteretic properties and skeleton curve of insulation hollow brick masonry under horizontal low cyclic loading have been researched. And then the factors that affect the anti-seismic capability of brickwork were studied.3. For the issue that the adhesive property of reinforced recycled concrete may reduce, the method of internal fracture test was used in this dissertation to obtain the bond-slip curves between concrete and bars with different kinds of combinations. And the influences of substitution rate, the shape and diameter of reinforced, anchorage length, thickness of concrete cover, and the admixture to adhesive property have been researched. And after obtaining the curve that the bonding strength changed along with the anchorage length, the fitting formula has been obtained. Furthermore, the bonding-slip relationship between bars and concrete was simulated with the methods of contact elements and nonlinear elasticity. And after contrasting the two methods, the suggestions on calculations were presented.4. For the situation that the recycled concrete are used a lot in situ concrete structure, in this dissertation four recycled concrete slabs with30%substitution rate and two common concrete slabs were made. And then the experiments on bending strength were conducted with the method of two-point loading, the parameters such as cracking load, cracking deflection and ultimate load of common concrete and recycled concrete were obtained. In addition, the recycled concrete slabs were reinforced and repaired by carbon fiber sheet under different unloading conditions. Comparing the bearing capacity and deformation before and after the reinforcement, observing the failure mode of construction members under different reinforcement conditions, the service conditions under which the recycled concrete flexural member can be reinforced by carbon fiber sheet were discussed.