| The plant mix hot recycling technology of asphalt pavement can effectively deal with the waste asphalt mixture,save energy and environmental protection,reduce the cost of road construction,and thus bring high environmental and economic benefits.At present,the research on plant mix hot recycling technology has become mature,but the mix design of plant mix hot recycling mixture,the research on key technology,the energy consumption emission and benefit analysis in construction engineering still need further research.Therefore,based on SMA-13 asphalt pavement plant mix hot recycling project of quanxia expressway,this paper systematically studies the plant mix hot recycling technology of asphalt pavement.First,obtain old asphalt from the old asphalt mixture from the project road section,test the content of old asphalt and relevant physical properties,and then prepare recycled asphalt;then,determine the optimal content of recycled asphalt binder by testing the basic physical properties of recycled asphalt binder,and further evaluate the high-temperature and low-temperature rheological properties of recycled asphalt binder;then,according to the determined recycled agent Mix proportion design of plant mix hot recycling mixture is carried out by mixing amount and old material proportion,and orthogonal test is designed to study the influence of rap preheating temperature,new material preheating temperature and mixing time on the performance of plant mix hot recycling mixture,so as to determine the best recycling process conditions;finally,the whole process and benefits of plant mix hot recycling are comprehensively analyzed.The main conclusions of this paper are as follows:(1)By analyzing the physical and chemical properties of the old asphalt recovered from the renovation of quanxia expressway,the results show that compared with the modified asphalt used in the construction period,the penetration and ductility of the old asphalt decrease significantly,and the softening point increases significantly;during the aging process of asphalt,the oxidation reaction occurs,forming the polar groups containing carbonyl and sulfoxide groups,namely carbonyl and sulfoxide groups Sulfone based substances.(2)The special regenerant and the old asphalt were selected to prepare the recycled asphalt.Through the comprehensive comparison of penetration,ductility,softening point and viscosity index with the original asphalt,the optimal dosage of the regenerant was determined to be 6%.The dynamic shear rheometer(DSR)and bending beam rheometer(BBR)were used to analyze the rheological properties of recycled asphalt binder at the optimum dosage.The results show that the low temperature performance of recycled asphalt binder is significantly improved compared with the old asphalt,and the high temperature performance is slightly decreased.(3)By adding 30%rap,Marshall design method was used to complete the mix proportion design of plant mix hot recycled SMA-13 asphalt mixture.The gradation design,the best asphalt aggregate ratio and the determination of new asphalt content were analyzed.The quality ratio of material to SMA-13 recycled asphalt mixture was obtained,and the leakage and dispersion detection under the best asphalt aggregate ratio met the specification requirements.(4)Taking rap preheating temperature,new material preheating temperature and mixing time as factors,the orthogonal test was designed to analyze the influence of each factor on the high temperature stability and water stability of recycled asphalt mixture.The influence order was:Rap preheating temperature>new material preheating temperature>mixing time.Combined with the results of orthogonal test,engineering experience and specification requirements,the recommended construction conditions are:Rap preheating temperature 130℃,regenerant heating temperature 145℃,new asphalt heating temperature 165℃,new aggregate heating temperature 180℃,total mixing time 65s.(5)Through the verification of the test road section,the pavement smoothness,construction thickness,compactness and surface water permeability coefficient meet the requirements of relevant specifications.Through the analysis and calculation of the material cost,fuel cost and equipment cost of the whole plant mix hot recycling technology,the unit cost of the material cost is 44.57 yuan/m~2,7.19 yuan/m~2 and14.73 yuan/m~2 respectively,compared with the ordinary hot mixing technology,the cost saving rate is 21.09%,-38.5%and-56.2%respectively,and the comprehensive cost saving rate is 6.3%;in addition,the plant mix hot recycling technology Compared with common hot mixing technology,it has certain environmental benefits. |
