Experimental Study On Mix Design And Fundamental Properties For Concrete Using Recycle Crushed Bricks Coarse Aggregate

Rational recycling of construction waste, could not only decrease the environmental pollution effectively, but also bring down the consumption of the soil, stone, sand and other natural resources for large-scale construction, contributing to sustainable development and bringing good social and economic benefits. So far, there are a lot of studies on the waste concrete as recycled aggregate, while a few studies on the concrete which using crushed bricks as coarse aggregate.Waste concrete and bricks take about 80 percent of construction waste. And the abandoned bricks take a larger part of construction waste in China, if these part of the construction waste could be rational using, the utilization of construction waste will be increase.The abandoned bricks which made of construction waste will be crushed and sieved, then used as recycled coarse aggregate to produce concrete for experimental study. In this paper, experimental research on fudamental properties of crushed bricks as coarse aggregate is carried out. The mixture ratio text of recycled concrete using 100% crushed bricks as coarse aggregate is carried out, and the compressive performance and shrinkage deformation performance are studied. The conclusions are given as follows.High absorption of water and low soundness are two distinctive features of recycled crushed bricks coarse aggregate.Two strength grades of recycled concrete, such as C20 and C25,which using bricks as coarse aggregate, are made out.Characterisitic value of cubic concrete compressive strength at the age of 28 days are 21.2MPa and 27.55MPa respectively. It indicated that the strength grade of recycled concrete which using bricks as coarse aggregate can reach C20 and C25.The strength of recycled concrete which using bricks as coarse aggregate grow slower with age than that of natural aggregate concrete, and at the same age, the strength value of waste brick aggregate concrete lower than that of natural aggregate concrete of the same strength grade.In nature curing condition, most of the shrinkage of waste brick aggregate concrete block is completed at the age of 28 days, then the increment speed of shrinkage ratio became slowly, and stabilized after the age of 60 days.In the standard curing condition, the change of ambient humidity has a greater impact on the shrinkage of recycled concrete block,in the period of 83 days, almost little shrinkage of recycled concrete, which using 100% crushed bricks as coarse aggregates, taken place.Based on the experimental study for compressive performance and shrinkage deformation of concrete which using 100% crushed bricks as coarse aggregate, the main factors affecting the strength, such as the curing age, and the main factors affecting the shirnkage deformation, such as the curing ages, the strength grade and curing conditions(the ambient temperature, the relative humidity), are discussed and analyzed. Based on regression analysis of test data,the formulas which estimated the strength of recycled coarse aggregates concrete are suggested, and the formulas which estimated the shirnkage deformation of recycled coarse aggregates concrete curing in natural environment are aslo given out.