Research On Materials And Structure Of Asphalt Overlay On Old Cement Concrete Pavement Based On Stress Absorption Interlayer

The researchers and practitioners of civil engineer have made massive theoretical analysis and testing appraises about the aspects including the mechanics how the reflected cracking and the delayed reflected crack were produced and expanded and the structure, material, design and the testing method of the overlay of asphalt concrete. At present the research is not enough comprehensive and thorough to the structure and design of the overlay of stress absorption interlayer. The paper made the further thoroughly studies about the new material of the overlay to the above. The paper has mainly carried on six aspects as follows:The first aspect is that the reason why stress absorption interlayer can decrease the stress concentration in theory is discussed. The fact that these parametric variation including the thickness of asphalt overlay, the modulus of stress absorption interlayer, the length of the initiate cracking, the cooling amplitude and axle load so on, has an effect on the stress intensity factor of stress absorption interlayer is analyzed. All these are based on the theory of the linear elastic fracture mechanics and the finite-element method by which the reason and expanding mechanics of stress absorption interlayer are analyzed. It is opened out that the stress concentration is decreased by the joint of the old cement concrete pavement and stress absorption interlayer in the joint through the mechanical analysis.The second aspect is to qualitatively study the crack control and the resisting tracking force of the overlay then determine the design parameter from the test room of stress absorption interlayer. The contrast test to the endurance failure of different overlay has been made by large fatigue machine and MTS in indoor ideal conditions. To evaluate the resisted reflecting crack of different asphalt overlay, especially the one of stress absorption interlayer, and validate the academic result. This article simulated some courses how the load and temperature reflecting crack based on the asphalt overlay had been produced and expanded. All these indicated that stress absorption interlayer is a good kind of material which can delay the expansion of the reflecting crack. The third aspect is to make some mechanical analysis to the stress's absorption interlayer then study the influence of stress absorption interlayer quantificationally as the variety of the design parameter. Some jobs were completed. The crack control mechanics of new-style overlay and other typical overlay to trial pavement and solid project was analyzed. And the vehicular load was compared to temperature load by mechanical calculation. Finally it is proved that stress absorption interlayer can decrease the vehicular load stress and temperature stress effectively under load.The fourth aspect is to discuss the design method of the asphalt overlay based on the stress's absorption interlayer. Some things are given including the control and design method of deflection based on stress absorption interlayer, the design of double control index and the minimal thickness which can meet the traffic. All these were completed on the basis of actual construction control and the observation result of working condition which were given by the trial pavement and solid project, the indoor tests and the calculated analysis. It means that the single-point's deflection should be less and equal than 0.14mm, and the deflection of bilateral plate edges should be less and equal than 0.06mm at the joint and crack of the coruer plate before overlay. The minimal thickness of overlay above stress absorption interlayer which can meet the traffic is 8cm.The fifth aspect is that the pavement performance of the special modifying asphalt binder with stress absorption interlayer and its effect and rationality are given, and which provided some bases to how to confirm the design parameter of the mixture of stress absorption interlayer. All these are completed by the research of the asphalt of stress absorption interlayer and the pavement of mixture.The sixth aspect is to exploit the new material of SamPave stress absorption interlayer on the basis of the above independently. The mixture of Sam Pave stress absorption interlayer is made up combined to the given material's gradation, and then builds the trial pavement.