Recycled Concrete Abrasion Resistance Study

The application of recycled coarse aggregate to concrete pavement will expand the scope of reuse of waste concrete, and that will be of great significance. Compared with the natural aggregate concrete, the wear resistance of recycled concrete is poor, and that has become one of the constraints that promote the application of recycled concrete, while the reports on the research of wear resistance of recycled concrete are rare. In view of these, this paper systematically studied the wear resistance of recycled concrete, and the main research content and conclusions are as follows:1. The basic properties of recycled coarse aggregate were studied. Compared to the natural coarse aggregate, the composition of recycled coarse aggregate is complex, and it is of lower density, higher porosity, faster water absorption, larger water absorption capacity, larger crushing index value, larger quantity of mud and lower robustness. According to the national standards (GB/T14685-2001) and recycled coarse aggregate quality standards, the basic properties of the recycled coarse aggregate which crushed by jaw crusher used in this paper meet the requirements, and the recycled coarse aggregate can be used to the preparation of plain concrete and reinforced concrete.2. The effects of the composition of raw materials on the wear resistance of recycled concrete were studied. When the replacement of recycled coarse aggregate was less than 40%, the wear resistance of recycled concrete was less different to natural coarse aggregate concrete, while the replacement of recycled coarse aggregate was lager than 40%, with the replacement of recycled coarse aggregate increased, the wear resistance of recycled concrete reduced. When the water-cement ratio increased, the strength of recycled concrete reduced, which also reduced the wear resistance of recycled concrete. When the maximum particle size of recycled coarse aggregate was 26.5mm, the tested recycled concrete showed the best wear resistance. When little change in strength of recycled concrete, the total volume of cementitious materials and the sand rate increased, and the wear resistance of recycled concrete reduced.3. The relationship between the wear resistance of recycled concrete and the strength were studied. The relationship between the wear resistance of recycled concrete (wear volume per unit area) and the compressive strength was quadratic parabola, and the relationship between the wear resistance of recycled concrete and the flexural strength was exponential, and compared to the flexural strength, the compressive strength can reflect the wear resistance of recycled concrete better.4. The correlative between the wear resistance of recycled concrete and the composition of raw materials was analyzed. Compared with the replacement of coarse aggregate, the water-cement ratio was of greater impact on the wear resistance of recycled concrete. When little change in strength of recycled concrete, the total volume of cementitious materials affected the wear resistance of recycled concrete more than the rate of sand.5. The technical means that improving the wear resistance of recycled concrete were discussed. Strengthening the recycled coarse aggregate by mechanical reinforce combining with chemical reinforce, the use of mineral admixture, adding steel fibers or polypropylene fibers, taking reasonable construction technologies, all of them can achieve the purpose of improving the wear resistance of recycled concrete.6. The wear resistance of recycled concrete can obviously improved by mechanical reinforces combining with polymer (PVA) immersion to recycled coarse aggregate. Judging from the results of improving the later (28d) wear resistance of recycled concrete, fly ash mix with slag and silicon did better than fly ash mix with slag, and fly ash mix with slag did better than fly ash; and when fly ash mix with slag and silicon, the selective content of FA was 10%, the content of SG was 15%, the content of SF was 6%; and when fly ash mix with slag, the selective content of FA was 16%, the content of SG was 4%;and the fly ash single-doped was 30%; the suggested volume content of steel fiber that increase the wear resistance of recycled concrete was 1.5%, and the content of polypropylene fiber was 1.0kg/m~3. The use of double stirring process and the finishing of recycled concrete can improve the wear resistance of recycled concrete.7. The GM (1, 1) prediction model building was based on gray theory, and that was checked of good prediction accuracy. The GM (1,1) prediction model can be used to predict the wear resistance of recycled concrete.