Research On Water Damage Mechanism Of Asphalt Concrete Under Moisture-temperature-loading Coupling Action

With the rapid development of highway cause,the sharp increase of traffic volumeand average speed makes the highway has been built to run overload,early damage of alarge area appears on the road,water has been the main factor of early damage of asphaltconcrete pavement,and water damage is the most important phenomenon,the mostharmful type of early damage.therefore,further study on water damage mechanism ofasphalt concrete under moisture-temperature-loading coupling action is conducive tofuther deepen the understanding of water damage to asphalt pavement.This paper first introduces the related theory of water damage mechanism of asphaltconcrete under moisture-temperature-loading coupling action,starting from the adhesionperformance of asphalt and aggregate by the surface energy theory,the use of asphaltand mineral aggregate adhesion model system,access the systems of asphalt and mineralaggregate adhesion work and surface free energy change,and thus to evaluate theadhesion properties between asphalt and mineral aggregate.The use of flexible variablehead sidewall penetration tester to test and get the relationship between differentporosity and permeability coefficient.By soaking Marshall test,dispersion test andfreezing and thawing split test,the performance of specimens at different temperatureand different conditions of freeze-thaw cycle were tested,and obtained the waterstability of asphalt mixture under moisture-temperature-loading coupling action.Inaddition,the study used CT instrument to scan the asphalt mixture specimens before andafter freeze-thaw splitting,to study the thaw splitting damage to the internal condition ofthe specimens.The main conclusions are as follows:1. The surface energy of aggregates is far greater than asphalt’s,the adhesion workbetween asphalt and aggregates is greatly influenced by aggregates.In adhesionprocess,the adhesion between SBS modified asphalt and basalt is well,in peelingprocess,the anti-stripping ability between SBS modified asphalt and limestone is thestrongest.2. The permeability coefficient of three types of asphalt mixtures(SMA-13,AC-16,AC-20) is directly related to the porosity.With larger porosity,thepermeability coefficient is getting bigger.The infection point position of three types ofasphalt mixtures is substantially the same as the initial damage threshold of asphalt pavement porosity,it’s between8%to9%.3. With the increase of porosity,the water stability of specimens under the influenceof water also increases.Mixtures with quicklime and hydrated lime can improve thewater stability,the hydrated lime content of4%is the best.mixtures with cement canhardly improve the water stability.4. As the temperature rises,the splitting strength of specimens of three types ofasphalt mixtures (AC-13,AM-13,OGFC-13) had a gradually decreasing trend.Splittingtensile strength and temperature showed a good correlation index,the correlationcoefficient is between0.92to0.98.5. From CT image analysis results,the water had obvious destructive effect onadhesion between asphalt binder and aggregate in the freeze-thaw process.The porositysignificantly increased after splitting where the initial porosity is large.And the positionand orientation of the injury development of specimen is closely related to the initialvoid distribution.Using damage variable can quantitative depict the water damage ofasphalt mixture under moisture-temperature-loading coupling action.