Aggregate Effect And Influence On Concrete Pavement

In China, the development of Cement Concrete Pavement has a relatively short history, particularly the Highway and freeway. Some of the new repaired roads which have been used for just a few years have emerged very serious problems affecting traffic safety and comfort, such as pavement wearing, cracking and so on. Because of the cost of repair we have to increase the durability of concrete. The main form of the road surface concrete destruction is fracture. Therefore the key to extend the life of concrete roads is to improve flexural strength. There are lots of researches on the influence of coarse and fine aggregate to road surface concrete, but most of them focus on one side. This paper mainly focuses on effects of the coarse aggregate, including lithology, the maximum size of coarse aggregate, size distribution of coarse aggregate etc. and discusses the function of coarse aggregate.The results show: lithology of coarse aggregate to some extend has influenced on road surface concrete, as the differences of absorbance of rocks cause fluctuations of W/C, which affect the bending strength of concrete; the influence of maximum particle size of coarse aggregate on the road surface concrete is biggest according to this research, including concrete rheology, flexural strength and concrete discrete; size distribution of coarse aggregate, rough surface and needle sets flake compound content play an important role in the rheology of concrete and mechanical properties of hardened concrete. Considering the flexural strength of concrete for the common grading 4.5MPa~5.0MPa, the appropriate largest size of coarse aggregate is 31.5mm~40.0mm; continuous grade is better than single-particle; the crushed stone is better than the pebbles; moreover needles flake content of gravel and coarse aggregate should not exceed 12%. Regarding to the flexural strength of concrete, there is a reasonable ratio of sand, when the mobility of concrete is best and the flexural strength is relatively largest. The gradation and the thickness of sand have an obvious effect to the road surface concrete. In preparation with the flexural strength (4.5MPa~5.0MPa) of concrete pavement, the best selection is two areas of sand, and must control the ratio of sand between 32%~34%. Improveing the processing quality of aggregate, suitably reducing the maximum particle size of coarse aggregate, guaranteeing good grain shape and particle size distribution of aggregate can greatly improve the durability of concrete.This research has a profound work on aggregate, but a further work is needed to the road surface concrete. If we fully realize this, we could control production. A link of construction, of course, raw materials (quality of coarse and fine aggregate) is very important. For how to choose aggregate of concrete pavement in design, how to control the quality of aggregate in construction, play the main function of aggregate in the concrete, this provides a theoretical basis.