Research On Preparation And Durability Of Recycled Aggregate Concrete With High Strength

At present our country is the largest country in the world urban construction scale and produce a large amount of waste concrete.In recent years the domestic and foreign experts and scholars have research the basic physical properties of recycled aggregate concrete and mechanical properties.But the recycled aggregate concrete strength value is low, and applied to the practical experience in engineering project also is less.Recycled aggregate concrete are restricted its wide application, and the study of the durability of recycled aggregate concrete has still not much.The recycled aggregates was produced by the proposed recycling process, to test the physical properties of the produced aggregate. High strength of recycled aggregate concrete was research its durability performance under satisfies the requirement.Including shrinkage, carbonation resistance, resistance to chloride ion penetration, such as resistance to sulfate erosion performance.Simple crushing aggregate was heated 1 h, then through the strip steel ball lapping machine for 0.5 h after grinding.The physical properties of recycled aggregates with above process were superior to simple broken recycled aggregates.This is because through the above process to mechanical activation of recycled aggregates, destroy weak regeneration of gravel particles or remove adhesion on the regeneration of gravel of cement particles, thus improve the quality of the recycled coarse aggregate. Experiments show that the compressive strength of the substituting rate of 50% of the aggregate replaced the rate of 30%of the fine aggregate and recycled concrete has reached the expected strength more than 50 mpa, satisfies the requirement of high strength concrete strength.. After achieving the expected intensity by comparing the test to examine the durability of recycled concrete. According to the present process with respect to the simple task of crushing process, durability index studied in this paper has been greatly improved, in which the subject process step is added during the grinding balls by grinding with the ball without contrast, studies herein durability are further improved.The replace rate of recycled coarse aggregate and recycled fine aggregate,mixing way, water cement ratio, the maximum size of recycled coarse aggregate,fly ash, the initial water cut of recycled coarse aggregate state effects on the performance of recycled aggregate concrete’s durability were also studied. With an easing of the recycled coarse aggregate content, the improvement of the durability of recycled concrete is obvious; When used with natural fine aggregate replacement of recycled fine aggregate, the durability of recycled concrete increase is more obvious; Adopt the mode of secondary stirring mixing way, also have obvious effect to improve the durability of recycled concrete; With the increase of adding amount of fly ash, to effectively improve the durability of recycled concrete. Carbonation resistance and shrinkage rate also have the same characteristics; Increase of recycled coarse aggregate size, enhances the shrinkage performance, but against the carbonation resistance, resistance to chloride ion permeability and chloride sulfate erosion resistance is bad; If using the saturated surface dry state of recycled coarse aggregate, can improve the shrinkage performance, resistance to chloride ion penetration performance and sulfate attack resistance, complete drying of recycled coarse aggregate, can improve the performance of carbonation resistance.