Study On Fiber-asphalt Mortar And Pavement Performance

With the rapid development of national economy,the increasing traffic in China leads to the serious vehicles overloading problems which put forward higher requirements to the asphalt pavement.In recent years,adding fibers in the asphalt mixture to improve the pavement performance has been getting more and more attention.Fibers can improve the micro-properties of matrix asphalt,making up the disadvantage of poor tensibility and low temperature brittleness of the asphalt mixture.In addition,the adsorption effect of fiber on asphalt pavement can reduce bleeding,increasing the high temperature stability of asphalt mixture.In this dissertation,with the help of dynamic shear rheometer and bending beam rheometer,effects of ratio of filler to asphalt(ROFTA),fiber type and content on high and low temperature rheological properties of asphalt mortars were investigated,and the strengthening mechanism of fibers on asphalt mortars and the interfacial interaction between fibers and asphalt were analyzed.The pavement performance of fiber-asphalt mixture was investigated,and effects of fibers,especially fiber type and content,on high temperature stability and waterproof capability of open-graded friction course(OGFC)were analyzed to explore the strengthening mechanism of fibers in OGFC.By comparing the high-temperature rheological performance of fiber-modified asphalt and pavement performance of OGFC,the relation between them was determined.The results were as follows.Fibers in the dissertation presented good oil absorbency and heat resistance,satisfying the practical pavement requirements.The optimal mixing temperature of fibers or deoiled asphalt(DOA)was 170 ?.With the ROFTA increasing,softening point of the asphalt mortars increased while the cone penetration decreased.The results indicated that,filler can obviously improve the thermal stability of asphalt and reduce the occurrence of permanent deformation at high temperature.Moreover,the increasing of the ROFTA raised shear strength of asphalt mortar.Similar to the improvement of ROFTA,fibers also increased softening points obviously while reduced the cone penetration of asphalt mortars.The results suggested that fibers improved anti-deformation of asphalt mortars at high temperature and then the shear performance.The high temperature performance improvement of DOA on asphalt mortar was similar to that of fibers,suggesting that the replacing fiber with DOA was technically feasible.Moreover,economic calculation showed the replacing fibers with DOA was economically feasible.The rheological performance of fiber asphalt showed,fibers can greatly improve the stability of asphalt mortars at high temperature to strengthen them.Fibers absorbed the light components in asphalt,forming a spatial network structure which favors the formation of a thick coating of mastic without asphalt draining down.As above,fibers effectively improved the adhesion and stabilization of asphalt mortars.However,the improvement of asphalt mortars was related to the fiber type.Cellulose fiber possessed a greater effect on asphalt absorption and stabilization than the other fibers(mineral and carbon fiber).Fiber-modified asphalt mortar was sensitive to temperature,and high temperature was favored for better crack resistance.The incorporation of lignin fiber,the high temperature rheological properties of asphalt mortars were unchanged.At the temperature investigated in this dissertation,the interfacial adhesion between lignin fiber and asphalt was stronger than that between limestone powder and asphalt.The pavement performance of fiber-modified OGFC showed,fibers improved the high temperature stability and water stability of OGFC.The reason is that fibers adsorbed a large amount of asphalt in OGFC,thickening asphalt film wrapped outside aggregate surface.In addition,fibers adsorbing asphalt or oil with the elongated shape were dispersed between asphalt mortar and aggregate,hindering the slide of aggregate particles and enhancing the cohesion between asphalt and aggregate.As a result,shear resistance at high temperature,rut deformation resistance and even the waterproof capability of OGFC were enchanced.The strengthening mechanism of fibers in OGFC mainly lies in the stabilizing effect,bridging effect,crack resistance effect and interfacial enhancing effect.The pavement performance of fiber-modified OGFC showed that,lignin fiber-modified OGFC presented the highest improvement which was related to the fine bridging effect and strengthening effect of lignin fiber.By comparing the high-temperature rheological performance of fiber asphalt and pavement performance of OGFC,a conclusion was drawn that the former can be used as an indicator of the later.