Study On Preventive Maintenance Technology Of Asphalt Overlay On Cement Concrete Pavement Of Guangxi Expressway

The maintenance of cement concrete pavement can be achieved by paving asphalt overlay above the old pavement.This method makes full use of the remaining life of old concrete face slabs and it also ensures certain traffic capacity of highway while improving driver's riding quality.Compared with other repairing methods,this method has little influence on both traffic and environment and has better economic benefit.However,the internal force existed in asphalt overlay has been extremely complicated due to many equally-spaced seams and irregular cracks in worn cement concrete pavement.And the great structural differences also contribute to this complexity,which existed between asphalt overlay above cement concrete pavement,semi-rigid base and rigid base.All these factors cause diseases of asphalt overlay during early age,such as cracks,rutting and slot.The above mentioned diseases occur in the cement concrete asphalt overlay layer,which does not mean the end of the service life of the overlay layer,so long as it is properly maintained in time,its road performance can be restored.Therefore,it is necessary to investigate the main diseases of asphalt overlay on cement pavement,analyze the formation mechanism of the disease,evaluate its using performance,and then formulate a scientific preventive maintenance program at the best time to slow down disease development.It's not only reduces the cost of road maintenance,but also the sustainable development of highway construction is also very important.Based on the investigation and analysis of asphalt overlay on old concrete pavement of Gui Liu Expressway and Nan Liu Expressway of typical expressways in Guangxi Province,this paper has proposed the graded classification methods aming at typical diseases of asphalt overlay,which is divided into three columns,five classes and eight types.It has also put forw ard the graded staging methods of different asphalt overlay diseases.At the same time,the area measurement method and the weight coefficient for the main diseases of asphalt pavement are put forward,which will provide important reference for the grading and maintenance decision of asphalt overlay.Deficiencies of existed evaluation models has been analyzed according to evaluations of service performance for asphalt pavement and characteristics of asphalt overlay in terms of dif ferent materials,structural forced patterns and diseases.This paper also proposes a new evalu ation method and recommends the corresponding weight coefficients and calculation formula of different evaluation indexes,including Overlay Condition Index(OLCI),Rutting Depth In dex(RDI),Skidding Resistance Index(SRI),and Overlay Structure Strength Index(OLSSI).The fuzzy hierarchy entropy multi-objective evaluation decision-making method is adopted.The weight coefficient of each sub-evaluation index is determined by the method of entropy weight,and the scientific significance of the sub-evaluation index weight coefficient is further demonstrated.Aiming at the reflection cracking and rutting of asphalt overlay on cement concrete pavement,the optimal timing of precautionary maintenance of asphalt overlay was determined by studying the characteristics of disease process of asphalt overlay.Finally,the decision-making method of asphalt overlay maintenance timing is put forward.At the same time,it is also verified that the cost-benefit method and life-cycle assessment method can be used to determine the optimal maintenance timing of asphalt overlay.At last,two main diseases of the asphalt overlay on the old cement concrete pavement of Liugui high speed in Guangxi region are: Reflective cracks and rutting,combined with the existing asphalt overlay preventive maintenance technology,decided to adopt joint grouting technology of asphat pavement and micro-surfacing rut repair technology Gui Liu high-speed typical sections of preventive maintenance.In order to achieve better filling effect,a high viscoelastic filling material,which is modified by SBS and rubber powder to matrix asphalt,is developed in this paper,and the properties of high temperature,low temperature and adhesion were studied.The results show that it has high adhesion,excellent elasticity and ductility,good performance of high and low temperature,for rutting disease of Gui Liu Road,mix design of micro-surfacing mixture is designed,and the Paving process of micro-surfacing is introducted.