Research On Control Criterion Of Deflection For Reconstruction Of Asphalt Overlays On Existing Cement Concrete Pavement

Many cement concrete pavements in operation have reached th e designed service life in China, and damages such as cracks and cavities beneath concrete slabs have appeared. Therefore, the maintenance and reconstruction of the existing cement concrete pavements have become an urgent problem to be solved for the highway management sectors. Paving asphalt concrete overlays on the existing cement concrete pavements is the most usual method, though which the performance of the pavements could be improved while the existing cement concrete pavement s could be reused to cut the cost and avoid construction pollution. It is an economical and effective reconstruction method. However, the problem of reflection cracks of the overlays has not been resolved completely and there is not an appropriate design method till now.Finite element analysis software A BAQUS was used to simulate the existing cement concrete pavements with and without dowel bars to analyze the deflection value and tensile stress of the existing cement concrete. With the deflection value of the existing cement concrete pavement as control criterion, three overlay structures with different base materials—CTB(Cement Treated Base), GM(Graded Stone) and ATB(Asphalt Treated Base)—were analyzed, and the deflection value and tensile stress of the overlay structures were researched. Taking the deflection and tensile stress as indicators, the equivalent modulus of elasticity of the existing pavement s under three different overlay structures were calculated by using software BISAR3.0, and the formulas to calculate the equivalent modulus of elasticity were fitted.The results show that the deflection and tensile stress of the existing cement concrete pavements with and without dowel bars both increase while the modulus of the base and subgrade decrease. The modulus of the subgrade shows more impact on the deflection and the smaller the modulus is, the bigger the difference is between the two structure. As for the three types of the overlays, t he tensile stress of CTB base is the highest which results in a lower equivalent modulus of elasticity and it is easy to appear reflection cracks, especially at the transverse joint area. Whereas, the base course consists of GM or ATB material leads to a lower tensile stress and the equivalent modulus of elasticity is higher, which means these two kinds of bases are much more appropriate for overlaying on the existing cement concrete pavement s.