Research Of Full-depth Cold Replace Recycling Technology

Most of Chinese highway pavement are built by asphalt concrete. A large amount ofasphalt in China has became damaged that have to be repaired and enter into the maintenancestage. Full depth asphalt pavement cold recycling technology recycles the old asphaltpavement and gravel base, then screening and adding the proper amount of cement, water,additives, mixing, compacting, forming a road can meet the requirements. Full Depth coldrecycling technology can eliminate surface disease and structural damage of the road surface,construction operability, not only can make the road to recover the former performance, butalso recycled the waste road materials, it is both economic and social benefits.The current research is analyzed by comparing different research status at home andabroad, the research plan is determined after the analysis. First, the original road situation wasinvestigated, retrieves the RAP raw material then tests its properties. The matching degreebetween old gravel base and asphalt surface were analyzed. Secondly, different types of mixeswere designed, after adjusting gradation mixing in different cement and water content, themaximum dry density and optimum moisture content were obtained. In order to research theinfluence of old asphalt mixture and cement to the recycling mixture’s properties, choose the20/80,33/67,40/60mix of three asphalt pavement and gravel basement layer, theunconfined compressive strength, splitting tensile strength, compressive modulus weretested. On the basis of these indicators, the cement stabilized recycled asphalt mixturemicrostructure was observed by SEM（scanning electron microscope）, explore the cementstabilized cold recycled asphalt material composition, strength, formation mechanism,characteristic microstructure.The results showed that with increasing of old asphalt mixture, the recycled mixture’sstrength was gradually reduced, and stability of temperature and water became worse. Theproportion of asphalt layer and grassroots have great influence on its mechanical strength, themixture contain more than5%cement can meet the technical requirements of streng. On theother hand, the mixture contain less than5%have low modulus level that range between600MPa to800MPa. The recycled mixture microstructure analysis showed that the presence ofold asphalt cement is not beneficial to the strength formation of recycled mixture.