Research On The Key Technologies Of Hot In-Place Recycling Of Asphalt Concrete Pavements

Hot in-place recycling of asphalt concrete pavements have been used for more than 10 years in our country. Hot in-place recycling is a highly integrated engineering, its project quality is deeply influenced by process parameters during the construction. The key factors affecting the quality of hot in-place recycling were deeply studied through the actual results investigation of the existing hot in-place recycling.Firstly, a large of amount of investigations had been made for Jiangsu province’s hot in-place recycling of freeway asphalt concrete pavements. Repairing effects of roughness, rutting and skidding resistance index by hot in-place recycling, and applicability for SMA were analyzed through data; the construction effect of different construction units and different heating equipment were compared.Secondly, cross sections of freeway were scanned by laser, the relationship between proportions of new asphalt mixture and rutting depth was analyzed by regression, the proportion of new asphalt mixture’s formula of hot in-place recycling based on rutting depth was established. The heating effect of hot in-place recycling by road bumps was studied by Abaqus, and milling suggestions were made to each grade of highway according to the study. Preventive effect of cracks and impact on the roughness was studied and contrasted to different methods of crack treatment through survey.Then, each indicators of pavement coring samples were detected and correlation analyzed with rutting depth, thus the current sampling method was found unreasonable, for these reasons new sampling method was given. Changes of the amount of new asphalt mixture during the construction process was not considered in current hot in-place recycling mix design, so a new method of mix design based on the variability of rutting depth was proposed, tested and verified.Finally, influence on the hot in-place recycling heating effect of bitumen aggregate ratio, porosity and interlayer water was simulated and studied through laboratory test. The quality testing indicators in existing norm lacking of effective detect and control method to the indicators that affecting pavement quality. So a new test method of thickness of the recycling layer to test construction quality of hot in-place recycling was made, and tested through actual project.