Research On Regeneration Technology Of Old Composite Pavement Reclaimed Material In Cement Stabilized Macadam Base

Due to the advantages of both full use of the high strength of cement concrete pavement and its good asphalt pavement performance,asphalt overlay on the old cement concrete pavement(commonly known as "white and black' pavement)has widely used in the old cement concrete pavement reconstruction project.However,the "white and black" pavement in early stage of our country has been faced with reconstruction or expansion for the second time.The "white and black" composite pavement is more complex when it is recycled,at home and abroad,there were few studies on the recycling of "white and black" composite pavement.This paper studied the mechanical properties,the performance of old pavement materials,the gradation design,mechanical properties and shrinkage properties of cement cold recycled materials in detail,so as to provide the experimental and theoretical basis for the future.According to different road structure layers reclaim "White and black" compound pavement old material.Reclaimed Asphalt Pavement was extracted and recovered then the content of recovery asphalt and aggregate performance were tested.The differences of coarse aggregate and fine aggregate of Reclaimed Aggregates from different sources,and comparing with natural aggregate were studied.The results show that both the Reclaimed Aggregates and the natural material can meet the performance requirements of most grades grass-roots.The crush value,soft stone content,and dust content below 0.075mm of Reclaimed Aggregates are larger than the natural aggregate,but the content of the needle-like sheet is small.According to the characteristics of Reclaimed Aggregates and Reclaimed Asphalt Pavement,different rates of reclaimed materials were selected,and the gradation design was carried out which is by means of classification and utilization.After comprehensive selection,C-B-3 grade was selected as the target grading,P·042.5 cement was used as binder,RA(concrete cement concrete pavement material)type and RA-RAP(composed of old cement concrete pavement and asphalt concrete pavement)type with RA content of 30%and 50%cement stabilized macadam material.The optimum moisture content and the maximum dry density were determined by three methods:compaction test method,vibration test method and static pressure method.The results show that the maximum dry density of the material decreases after adding RA and RAP to the cement stabilized macadam.After the addition of RA to the cement stabilized macadam,the optimum moisture content of the material is significantly increased,can slightly reduce the optimum moisture content.The mechanical properties and shrinkage properties of cement stabilized macadam were tested.The results show that the addition of RA in the cement stabilized macadam base layer can effectively improve its mechanical properties,the addition of RAP to the recycled cement stabilized macadam has little effect on its strength properties.Under the other conditions unchanged,the cement is within a certain range,the higher the dose,the higher the temperature of health,the higher the degree of compaction of the mechanical properties of the specimen is stronger;vibration molding than the static compression of the mechanical properties of the specimen;RA incorporation will reduce the shrinkage of the material,in the regeneration of cement stability The inclusion of RAP in the gravel material can reduce the sensitivity of the material to water and temperature and improve the shrinkage properties of the material.Regeneration technology of old pavement material for road base course,which simplifies the construction process,saves materials,has a fast recovery rate,ensures the quality of recycled materials,mixes evenly,and protects the environment.It has good economic and social benefits and resources and environmental benefits.