The Numerical Simulation And Influence Of Aggregate Gradation On The Compressive Strength Of Recycled Aggregate Concrete

In recent years, for the fast development of urbanization, construction waste generated by large-scale construction and city rebuild have occupied 30-40 percents of all city waste. Concrete debris, the main component of construction waste, can be produced recycling aggregate by crashing, cleaning and sieving. Rrecycling aggregate can produce recycling concrete by replacing all nature aggregate or part. Recycling concrete debris not only meliorate the shortage of nature aggregate and resource, but also avoid expropriate mass of land for disposing construction debris. It is on the elementary phase of the recycling concrete study in China now, studies focus on the basic performance of recycling aggregate and recycling concrete. There is no sane technology, regulation and criterion yet.For the leitmotiv of practical application, this paper studied the surface character of recycling aggregate, the compressive strength of recycling concrete with different aggregate grade and presented granule-spring model(GSM) to simulate the compressive strength of nature concrete and recycling concrete. The detailed content as follow:(1) Estimated the generated quantity of concrete debris in recently years in China based on annually cement quantity or construction area, concluded that the generated quantity of concrete debris is 0.18 billion tons in 2003, capitation quantity is 0.12 tons. Then this paper forecasted the concrete debris in next 20 years by regress method and gray method respectively, concluded that the rise rate of concrete debris generated quantity is more than 3 percents every year in next 20 years.(2) Applying fractal theory to study the surface character of recycling aggregate, presented the fractal function of size distribute, aggregate grade, aggregate lacuna rate, aggregate face-area and aggregate roughness of recycling aggregate, for the compressive strength analyse which based on aggregate face-area of recycling concrete provided theoretical foundation.(3) The actual concrete grade criterion is not applicable to recycling concrete because of f surface performance between nature aggregate and recycling aggregate. After milling recycling aggregate, we find that the workability and compressive strength of recycling concrete made by milled recycling aggregate is batter than general recycling concrete. This paper presented thatγ, which is the ratio of cement that can enwrap the whole aggregate to entire cement, can be a key index for analyzing the strength of recycling concrete.(4) This paper presented a granule-spring model in which aggregate is rigid solid and mortar is spring to simulation the compressive strength of ordinary concrete and recycled concrete with different aggregate grades. The results indicated that GSM was applicable to simulate ordinary concrete, but when used to simulate recycled concrete, the influence of surface area must be considered.