High Performance Approaches And Properties Of Recycled Aggregate Concrete

With the development of high strength and high performance concrete, it takes people's attention on the high strength and high performance of recycled concrete. Reinforcing methods of recycled aggregate, the high strength and high performance of recycled concrete are systematically studied in this paper. The main contents and conclusions of the paper are as follows:1. According to the relevant standards, codes, documents and test dates, the quality requirement of the basic nature of recycled coarse aggregate is summarized. Recycled coarse aggregate composition analysis and relative surface roughness experimental method are given; water absorption experimental method is improved.2. The quality of recycled coarse aggregate is obvious improved by mechanical reinforce combining chemical reinforce. The most obvious effect of method is the one treated with 3 % HC1 after mechanical reinforce, then 1%PVA, whose apparent density is 2590kg/m³, water absorption is 2.7 %, crush index is 7 %, separately increase 1.6%, reduce 50% and 56% than untreated one.3. The rule of fractal dimension about compressive strength, flexural strength and split-tensile strength (3d and 28d) on high-strength recycled aggregate is similar with low-strength recycled aggregate. It is not suitable to limit better range of recycled aggregate grade with the standards of natural aggregate. Optimized recycled aggregate grade is d_MAX=19mm, D=2.7.4. Mixture ratio of fly ash and slag as FG is optimized according to the recycled coarse aggregate characteristic; and mixture ratio of fly ash, slag and silica fume as UFS is optimized. The complex effect of mortar with FG at 28d is 0.25%; the complex effect of mortar with UFS at 28d is 9.41%. UFS generates more compound pozzolanic effect than FG.5. Recycled concrete strength and toughness can be improved by combining potentiation effect of steel fiber and expander. C50 self-compacting concrete made with recycled coarse aggregates can be mixed by adjusting sand proportion, binder material, and mixing mineral additive.6. Mineral additive, steel fiber, expander and reinforcing recycled aggregate can improve chloride permeability, elastic ratio, cracking, and reduce dry shrinkage of recycled aggregate concrete. And their compound effect is the most significant.7. The cycle index of recycled concrete can be increased by optimizing mixture ratio of recycled concrete. It is feasible to realize the multiple circulation of recycled aggregate concrete.