Study On The Application Of Granite Asphalt Mixture Overlay On Old Cement Concrete Pavement

In Pearl-River Delta District, many concrete roads need to be maintained because of the coming of design period or the damage due to the sharp increase traffic. Asphalt overlay on old concrete pavement, one form of concrete pavement reconstruction, is liable to reflection cracks because of the discrepancy in materials and the existence of joints and cracks on the old PCC. With the development of highway construction, conventional materials such as basalt and limestone in this region are becoming scarce, which make the highway workers turn sight to granite with abundant reserves out of the consideration of using local materials and reducing project cost. This paper, Supported by Guangdong Highway Administration Bureau science and technology project "Study on the Application of Granite in Asphalt Mixture Overlay on Old Cement Concrete Pavement in Pearl-River Delta District", aims at delaying reflection crack and improving water stability and thermal stability of granite asphalt mixture, and the application of granite asphalt overlay on old PCC is studied. It is important for the reduction of engineering cost and the avoidance of resources overexploitation.Based on the pavement reconstruction program of Chencun section of Provincial Highway S112 in Foshan, Guangdong Province, the damage situation and bearing capacity of old concrete pavement were investigated and the proposal of treating was made; The load and thermal stress in joint area of the asphalt overlay was analyzed by means of pavement structure 3D finite element model, which is helpful to pavement structure design and material selection; According to the performance of asphalt overlay on old PCC, material composition design of granite asphalt mixture was conducted from raw materials, adhesion test, gradation design and road performance of granite asphalt mixture; Based on the construction of experimental road, the application of granite in the surface course of asphalt overlay on old concrete pavement and the evaluation of performance of experimental road were studied finally. The results show that:(1) The relative error of tensile stress at the overlay bottom calculated with ANSYS and HPDS2006 is 3.15%, which indicate that it is feasible to analyze overlay structure stress with ANSYS;(2) The measures of paving AM layer or geotextile between old cement concrete pavement and asphalt overlay can delay reflection crack effectively, and the efficiency of AM-20 layer 7cm thick combined with stress-absorbing interlay 2.5cm thick is highest, whose maximum tensile stressσ1,, maximum shear stressτmax and effective stressσe reduced by 78.6％,82.9% and 84.4% respectively than overlay structure without anti-cracking measures for the case-based asphalt pavement structure;(3) According to the expansion patterns of reflection crack, the evaluation process of controlling flexural-tensile and shear reflection cracking of asphalt overlay on cement concrete pavement is proposed, and the evaluation of the case-based asphalt pavement structure indicate that it can meet the requirements of anti-cracking;(4) The water-boiling method by extending boiling time can judge the contribution of anti-stripping agent in improving adhesion between aggregate and asphalt accurately and evaluate the thermal stability of anti-stripping agent to a certain degree, which is beneficial to anti-stripping agent selection;(5) The granite asphalt mixture's water stability and thermal stability greatly elevated and come up to specifications of high temperature, moisture zone when adding selected morlife300 anti-stripping agent;(6) The granite asphalt overlays built with normal construction technology have a good performance in compactness, roughness, permeability and skidding resistance when the technical measures of delaying reflection crack and improving adhesion between aggregate and asphalt.The research results herein can provide proper theoretical support and technical guidance for the application of granite aggregate in asphalt overlay on old PCC as well as the surface course.