Laboratory And Field Evaluation Technique Of Asphalt-surfaced Pavement Pothole Patching Material

As one of the most common and annoying distress types of asphalt-surfaced pavements,potholes embarrassed drivers and maintenance agencies all the time.Due to the lack of effective laboratory and field evaluation methodology and standard of patching materials,the quality of patching materials is hard to be assured,which leads to inefficiency restoration,repeatedly repatching and unnecessary economic loss.This paper intends to establish the laboratory and field evaluation methodology of pothole patching materials,which will present guideline of maintenance decision for highway maintenance agencies.As the periodic peak of highway maintenance approaches,there is broad application prospect for this research.Simultaneously,the research respond to the preventive highway maintenance strategy of the state Ministry of Transport,and is of great strategic and practical significance.Firstly,the evaluation content and methodology of pothole patching materials was studied.The common distress types of pothole patches and its causes were summarized via literature and field survey,and the law of pothole interface failure mechanism was identified by numerical simulation.On this basis,the evaluation content was identified by analyzing materials performance demand,evaluating the workability,pavement performance and pothole interface adhesive performance of patching materials.Initial deformation resistance test,composite beam bending test and oblique shear test was designed to evaluate the initial strength of patching,anti-cracking and anti-shearing performance of pothole interface.The existing laboratory test procedure was modified,including penetration test,rolling sieve test,modified marshall test,modified freeze-thaw splitting test and rutting test.Secondly,the technical specification of pothole patching materials was studied.Laboratory tests were conducted to evaluate the performance of four cold patch asphalt mixtures(CAM)and two hot-mixed asphalt mixtures(HAM).The technical specification of patching materials was proposed by theoretical study referring to the test results,relative standards and research findings.In result,recommendation was made that CPA should meet the following standard,1≤W≤4 or G≥3 for workability,d≤mm for initial strength,mr≥60%for cohesion,MS≥3kN for mature strength,TSR≥70%for moisture susceptibility,DS≥600times/mm for high-temperature stability.Recommendation was made that HMA should meet the following standard,MS≥5kN for mature strength,TSR≥75%for moisture susceptibility,DS≥800 times/mm for high-temperature stability.Recommendation was made that the pothole interface should meet the following standard,εB≥1500 for interface anti-cracking performance and τ≥1.0 MPa for interface anti-shearing performance.Lastly,the quantized evaluation methodology of field performance was studied.Quantized indexes were proposed for field performance evaluation by theoretical study,including Average Patch Survival Rate RPS,Expected Average Repair Life REXP.Recommendation was made that REXP≥20 weeks for CAM and REXP≥104 weeks for HAM,in the range of specified REXP,a minimum RPS of 60%is recommended.Field experiment was conducted for the laboratory materials,and Unit-cycle Patching Cost index C0based on RPS was proposed,which presents guideline of maintenance decision making for highway maintenance agencies.