Study On The Heating Technology In Asphalt Pavement In-place Hot Recycling

Hot in-place recycling of asphalt is a rapid,economic and environmental friendly asphalt pavement maintenance technology.The heating process of asphalt pavement has some flaws,such as serious pollution,low efficiency,and large temperature gradient,which leads to an inhomogeneous heating process,lower underly temperature and broken aggregates,thus the construction quality will be affected.In this thesis,heat transfer mechanism of asphalt pavement,thermal conductivity,and heating technology were researched through theory and experiment.Based on the assumption of one-dimensional,continuous and homogeneous heat transfer during the heating process of asphalt pavement,a simplified model was adviced,asphalt pavement inner temperature field in the heating process was analyzed with the explicit difference method.The thermal conductivity of asphalt pavement was a major influence on the heat transfer efficiency,it also shows various and complicated characteristics,There is no way estimating the thermal conductivity of asphalt pavement accurately by the theoretical method.a test device used in examining the thermal conductivity of asphalt pavement was developed based on one-dimensional heat transfer model and protecting hot plate method,which overcomes the defect of low temperature and slow speed of traditional thermal conductivity test device,and it can test asphalt pavement's thermal conductivity conveniently and quickly.an experiment device to heating asphalt pavement was invent to test the different deep asphalt pavement temperature and reasonable value of heat flux in the heating process.the results indicate that,the heat transfer model of asphalt pavement in hot in-place recycling is right,the internal factors influencing heating efficiency of asphalt pavement are the thermal conductivity,specific heat capacity and density,the external factor is heating flux.the heat flux density of asphalt pavement should be adjusted according to the heat transfer ability of asphalt pavement so that the asphalt will not over aging and has the highest heating efficiency.a new continuous variable power heating method for asphalt pavement was proposed.By adjusting the heating power in the heating process can keep the surface temperature of asphalt pavement at 180 ?,to improve the heating efficiency,decrease the energy used,solve the problems of asphalt surface over aging and near-bottom temperature lower in the traditional heating method.According to the thought of continuously variable power heating and in the light of asphalt pavement heating machine's structure and power control's characteristic,a segmented power control method was proposed,which can achieve continuous variable power heating on the asphalt pavement without changing the structure of the heating machine.Experiments were done to verify the effectiveness of variable power control method.The conclusion of the study has been successfully applied in the industrial prototype,which has the guiding significance for engineering application.