Influence Of Quality And Substitution Rate Of Recycled Coarse Aggregate On Durabilityof Recycled Concrete

The durability failure is one of the important reasons that cause the loss of the concrete structure and the early end of the service life. Because of the huge economic losses caused by the disease of durability, the problem is becoming more and more serious.Because of poor quality of recycled aggregate, the durability of recycled aggregate concrete is often not guaranteed. In this paper, we use particle shaping and organic silane waterproofing agent to strengthen recycled aggregate, and study the durability of recycled concrete in order to improve the theoretical basis for the wide application of recycled concrete.With the support of national natural Science Foundation of China（51378270）, this paper carried out the following research work:1. In accordance with the strengthening method of recycled coarse aggregate, we prepared six different quality of recycled coarse aggregates: the simple crushing recycled coarse aggregate; the particle shaping recycled coarse aggregate; twice particle shaping recycled coarse aggregate; the simple crushing and chemical enhancement recycled coarse aggregate; the particle shaping and chemical enhancement recycled coarse aggregate; twice particle shaping and chemical enhancement recycled coarse aggregate.2. The influence on durability, workability and capillarity of different quality, the amount of cement and substitution rate of recycled coarse aggregate by physical and chemical enhancement were studied.As the common aggregate, the simple crushing recycled coarse aggregate is prepared by conventional production processes, the other five kinds of aggregates is obtained after physical and chemical strengthening method. The results show that, when the amount of cement is 400 kg/m³ and substitution ratio is 50%, compared with nature concrete, water consumption of SBA recycled coarse aggregate concrete increases 3.2%, FA and SA recycled coarse aggregate concrete fell by 3.9%and 3.4% respectively; compared with nature concrete, the amount of capillarity of SBA increases 1.8×10^-12m²/s and the amount of capillarity of SBA-SI recycled coarse aggregate concrete fell by 2.1×10^-12m²/s; compared with SBA recycled coarse aggregate concrete,carbonation depth of FA and SA recycled coarse aggregate concrete fell by 10.1% and 12.4% respectively; compared with SBA recycled coarse aggregate concrete,cycles of freezing thawing FA and SA recycled coarse aggregate concrete increases 25 times and 50 times respectively; compared with SBA recycled coarse aggregate concrete,contraction percentage of FA and SA recycled coarse aggregate concrete fell by 16.3% and 18.1% respectively.