Study On Quality Control Of Asphalt Pavement Based On Heterogeneity

For a long time, asphalt pavement has existed many early diseases that are difficult to beeffectively solved. Within three years of highway coming into service, different degree of pitslot, bleeding, rutting and other diseases of asphalt pavement occur frequently. Local surveyresults show that these are localized disease type; it can be seen that the diseases are causedby the heterogeneity of asphalt pavement.The heterogeneity of asphalt pavement is a kind of deviancy that the actual indexes oflocal pavement exceed designed and specification required indexes in the period of materialselection, material composition design, mixture production and construction, which bringsabout unacceptable distinction of expectations of pavement performance and the design afterpavement construction; thus service capacity and service life of asphalt pavement areinfluenced. Reasons that can cause heterogeneity include material straggling, grading controldiscrepancy, stability of equipments, quality control differences in construction organizationand so on.Early diseases and causes of asphalt pavement were analyzed and results showed thatprincipal influence factors of quality heterogeneity was gradation segregation, temperaturesegregation and weak compaction. All kinds of heterogeneity detection technologies includingtraditional and emerging technologies were discussed. Non nuclear density gauge combinedwith laser grain meter could be utilized in the direction of surface and depth to quantitativelydetect the heterogeneity of asphalt pavement, which can meantime detect transverse,longitudinal, vertical and local heterogeneity.Mechanics index and performance index such as high temperature stability, lowtemperature stability and water stability of the mixture of different levels of segregation wereanalyzed to quantitative study correlation between segregation degree and pavementperformance. Hamburg rutting tester was applied to analyze the relationship betweensegregation degree and high temperature stability and water sensitivity. Results showed thathigh temperature stability of the segregated mixed coarse aggregate surpassed that of segregated mixed fine aggregate. And high temperature rutting resistance of segregated mixedcoarse aggregate decreased along with the increment of segregation degree. Test resultsrevealed high temperature stability could not be completely evaluated by individual indicators;various indicators were needed comprehensively. Water stability of segregated mixed fineaggregate was superior to that of segregated mixed coarse aggregate. When segregationdegree was above moderate, water stability of mixture had no visible difference, whichindicated that coarse aggregate segregation had greater water stability sensitivity.Whole process quantitative analysis of temperature segregation, weak compaction andgradation segregation in local mixture construction site was conducted. Grey correlationdegree analysis method was adopted to analyze different factors influencing weights; resultsmanifested factors that affected heterogeneity of asphalt pavement could be sorted byinfluence degree, namely, pavement compaction, mixture gradation and mixture temperature.Pavement compaction is of particular importance to control compactability index. At Firstdosage of asphalt should be controlled in mixture gradation; secondly, favourable effectscould be achieved by using average segregation rate to assess aggregate differences.Temperature segregation mainly happened in the rolling phase; special attention should bepayed to control mixture temperature in initial pressure stage.In accordance with measurement and regression analysis of aggregate averagesegregation rate, compactability index, initial pressure and re-pressing in construction stage,pavement density predicting model and voidage predicting model were put forward. Theheterogeneity of pavement construction quality could be evaluated rapidly and simplely.