Study Of The Performance And Structure Of The Asphalt Concrete Overlay On Highway

Paving asphalt pavement on the old concrete pavement is a common effective technique for pavement renovation. It has the advantages of short construction period, little side effects for transportation and good service after renovation. So it has been the common measure to improve the pavement performance, promote the carrying capacity and prolong the service deadline. But during the use of overlay, it easily emerges the reflect cracking in asphalt concrete pavement because of the original crack in cement concrete, and this brings severe negative influences on the life of pavement. Today there has not mature design of overlay though having had research and test on this aspect in our country. It was necessary and feasible to study the design to prevent reflecting cracks on the asphalt overlaid on the old cement concrete pavement.Contrasting the mechanics performances of asphalt mix with different types, we can conclude that for the same type of mix, the strength of tensile and compress,the modulus of bend and destroy compressibility will increase with the aggregate changing much more fine, especially, the modulus of rebound compress increases obviously. The strength of bend is improved and the performance of compress is weakened when the fibres are mixed into asphalt concrete, at the same time, the capability of deformation is enlarged and the modulus of bend and destroy compressibility were decreased. From this we can conclude that fibre can enhance the performance of deformation and make the durability of asphalt concrete pavement increased.In this paper, the mechanics performances of the old cement concrete pavement overlaid with asphalt concrete are analyzed with the finite element analyse theory, and using ANSYS, software of the finite element analysis, the mechanics performances of two types of asphalt mixture overlay with different thicknesses are analyzed, and also the mechanics infection due to the changes of cement concrete thickness and elasticity modulus are analyzed.Results show that: max shearing strength decreases with the thickness of asphalt increasing, the average decreasing value is 1.6%/cm. And the value decreases withthe modulus of rebound compress of overlay increasing, and also decreases with cement concrete elasticity modulus increasing. At the same time, the dynamic stability tests of asphalt concrete with different thicknesses also show that when the overlay thickness of asphalt concrete increases from 5cm to 16cm, the dynamic stability decreases about 50%.By analyzing the tests and theory, we can conclude that under the vehicle loading the best asphalt overlay thickness for preventing reflecting crack should be 10cm-16cm.