Study On Performance Of Asphalt Macadam Pavement Sealed By Slurry Seal And Its Application

Asphalt macadam pavement sealed by slurry seal consists of a asphalt macadam covered by a slurry seal, the compound pavement can develop strong suit of these two kinds of pavement, while avoiding the shortcoming of them in the mean time. At present, there are not any research reports about the performance, design method, construction technology of the compound pavement, so in the dissertation, the pavement performance of compound pavement are investigated by experiment and numerical simulation. Then, based on the construction process and investigation in-situ of Hu-Liu experiment pavement K29+500-K43+000, design parameter, construction technology and building cost of compound pavement are investigated, a design and construction guide is also given, here some research results and project experiences concerned are considered.The content and investigation results of dissertation are given as follows.(1) Permeability test is performed to study the permeability of slurry seal asphalt macadam compound pavement, test results show that the permeability of compound pavement rest on the slurry seal above it, slurry seal with a fine gradation or more water can acquire a better permeability resistance, and give a proper impaction after initial setting of slurry seal may acquire a better dense surface.(2) Rutting experiment results of Slurry seal asphalt macadam compound pavement show that the rutting resistance ability of compound pavement lies on the lower asphalt macadam. Asphalt macadam with an S type gradation can acquire a good rutting resistance ability, and the coarse aggregate content of asphalt macadam should be about 65-85 percent. The rutting resistance ability of compound pavement is better than it of single asphalt macadam pavement.(3) Low-temperature bend experiment is performed to investigate the low-temperature cracking resistance of compound pavement. Form the experiment results, it can be gotten that the low-temperature cracking resistance of slurry seal above the compound pavement play an important role in improving the low-temperature cracking resistance of whole compound pavement, and the low-temperature cracking resistance of compound pavement is poorer than it of asphalt concrete pavement, while is as good as it of asphalt macadam pavement. SBR modifier can improve the low-temperature cracking resistance of compound pavement.(4) Numerical method has been used to compute shear stress of compound pavement in order to analyze such distress as shoving, sliding and loss of slurry seal. Analysis results indicates that with increasing of tire load, coefficient of friction and tire pressure, shear stress is increment, but shear stress is decreasing while applied a higher temperature, and there is a great probability of shearing yield in hot season. To evaluation the interlayer bonding strength between slurry seal and asphalt macadam, an experimental setup is designed on the basis of improved shear tester, with the aim to model well the actual condition of loaded pavements, experimental results show that the interlayer bonding strength between the slurry seal and asphalt-macadam bottom layer decreases with increasing temperature. Taking some different measures to improve interlayer conditions of pavement can affect obviously the bonding strength, such as using asphalt-macadam mixture with big nominal grain size or making the pavement surface coarse by chisel.(5) Mesoscal FEM method is used to analyze the factors in effecting anti-reflective cracking of slurry seal asphalt macadam compound pavement, the relationship between pulling stress of compound pavement and the factor in effecting it is also gotten. The numerical results indicate that the performance of anti-reflective crack of compound pavement with more asphalt content is better than that with less asphalt, the performance would also be better if compound pavement is separable from old pavement near the crack of it or with a deeper depth, numerical results also indicate that the performance of anti-reflective crack of compound pavement with gap-graded asphalt macadam is better than of it with continuous-graded asphalt macadam. The method of brittle coat is also used to analyze the stress distribution of reflective crack of compound pavement, laboratory results show that the crack of brittle coat propagated around the macadam, and stress concentration occurs at the interface between the macadam and asphalt mixture. Interface between macadam and asphalt mixture in the region of stress concentration is most dangerous in pavement.(6) Based on the construction process and site investigation of Hu-Liu experiment road K29+500-K43+000, design parameter, construction technology and building cost of the compound pavement are investigated. The research results indicate that the compound pavement is a useful pavement and its pavement performance is good, design parameter and construction technology applied in the experiment pavement is feasible, building cost of compound pavement is lower than it of granule asphalt concrete, while almost correspond with coarse asphalt concrete. A design and construction guide of compound pavement is given based on the investigation results, here some expert's experiences and research results concerned are also considered.