Study On The Technology Of Hot Plant Recycled Porous Asphalt

The application of porous asphalt in China has been increasing in recent years.It is an important topic to provide a maintenance measure which is resource conserved,environment friendly and with high efficiency.The high-quality aggregates and high-viscosity bituminous materials of porous asphalt are considered to be recycled and reused.The system of the porous asphalt maintenance technology is to be improved by combining different types of maintenance methods.In this case,the research on hot plant recycling technology of porous asphalt was carried out.The study was performed based on the porous asphalt section of Yanhai highways in Jiangsu Province,which has been used for more than 12 years.In the research,the ageing mechanism of and the regeneration effect of high-viscosity modified asphalt were analyzed.The gradation design for the "skeleton-void" structure and performance analysis of the hot recycling porous asphalt mixture were conducted.The optimal RAP content was determined.A test section was paved to determine the construction process of the plant-mixed hot recycling porous asphalt.Through this study,a key technology system for hot plant recycled porous asphalt was established.It provided a technical support for the maintenance of porous asphalt in the future.Meanwhile,application of new technologies,such as the regenerant for porous asphalt,hot recycling equipment,was realized.Firstly,the road condition and disease development trend of the existing porous asphalt were investigated.The aggregate gradation,performance of recycled RAP materials,and the aging performance of high viscosity modified asphalt were evaluated.By means of Marshall stability test,splitting test,Cohesion test and dispersion test,the performance of the old porous asphalt was analyzed.The research shows that the pavement recovery asphalt and aggregate can meet the requirements of hot recycling technology.The damage of the whole pavement structure is small,which can be ignored.The porous asphalt is suitable to be maintained by milling the old surface layer and repaving the recycling porous asphalt mixture.Secondly,the ageing characteristics of the high viscosity modified asphalt extracted on site and the recovery effect were observed.Two kinds of high-viscosity modified asphalt were prepared by indoor simulated ageing procedure.The component analysis,infrared spectroscopy and other microscopic methods were used to detect and analyze the ageing tendency of asphalt performance under different aging conditions.By adding different types and proportions of regenerants,the effects of regenerant on the recovery effect of aged high viscosity asphalt were compared.Base on the analysis,the type and amount of the regenerant to be applied in this study were finally decided.Then,the design and performance observation of the hot plant recycled porous asphalt mixture were carried out.The gradation design method for the hot plant recycled porous asphalt mixture was established and the optimum ratio of oil was determined which leads to a large air void content.Through comparative analysis of key technical performances such as hightemperature bearing capacity,anti-raveling,anti-aging,low-temperature resistance,and water stability of different old material mixes,the optimal RAP material content for this project was determined.The mixture was considered to achieve an optimal performance and functional properties.Finally,with the paving of a test section,the construction process of the plant-mixed hot recycling porous asphalt was studied.Through the analysis of the influences of moisture content of RAP material,mixing temperature,material placement order,and mixing time,the mixing process and control temperature were determined.At the same time,key indicators for paving and roller compaction were put forward.By investigation of the performance of the hot plant recycled porous asphalt mixture and the measurement of the road surface characteristics,including friction coefficient,texture depth and permeability coefficient,the performance of the hot plant recycled porous asphalt halt was evaluated.And the feasibility and rationality of the construction process were verified.