Experimental Studies On The Special Fine Sand Preparation Of Recycled Coarse Aggregate Concrete

In recent years, Handan generated a lot of construction waste due to urban construction. The coarse sand, medium sand resources is shortages, and the fine sand is rich in resources. Therefore, this experiment after processing of construction waste as coarse aggregate, fine sand as special aggregate, to preparation the low strength grade of concrete, and to test its workability, compressive strength, shrinkage properties and economy of experimental research.This test uses orthogonal design, comparative tests, carried out research on the performance of concrete. Orthogonal design with water-cement ratio (0.50,0.53,0.55), sand ratio (26%,28%,30%), recycled coarse aggregate replacement rate (10%,30%, 50%), empty as factors, establish L9 (34) pilot program table. Orthogonal design scheme to study the concrete slump, compressive strength, the results showed that:the most important affected factor is sand in the workability of concrete, the reasonable sand rate of 28%. The workability of concrete recycled coarse aggregate effect same as the sand rate, the best content is 30%; the most important factor affecting the compressive strength of concrete is recycled coarse aggregate replacement ratio, and compressive strength of concrete with recycled coarse aggregate replacement rate increased decreased.On the basis of the test results on the orthogonal design, selection of recycled coarse aggregate replacement rate (0%,10%,30%,50%,70%) preparation of different water-cement ratio (0.40,0.45,0.50) of concrete, its slump, compressive strength, shrinkage performance, economy pilot study. The results showed that:recycled coarse aggregate replacement rate of 30%, its best workability of concrete, and 28 d compressive strength were 48.0 MPa,43.6 MPa,46.8 MPa formulated to meet the strength requirements; concrete shrinkage with age the variation is:0-28 d, a faster rate of contraction; 28～60 d, the contraction rate decreases, but continues to shrink; 60 d after contraction basically stable. Economic analysis showed that special preparation of sand and recycled aggregate concrete save 25 yuan/m3 compared with the same intensity level of ordinary concreteThrough the above analysis we can see when the recycled coarse aggregate replacement rate of 30%, sand rate (the fine sand) was 28%, and its workability, compressive strength, shrinkage performance met the performance requirements of the corresponding ordinary concrete, while saving costs. Therefore, the use of specially formulated sand recycled coarse aggregate concrete is feasible.