Study On Rheological Performance Of Asphalt Binder And Asphalt Mortar

Hot mixture asphalt is a mixed system of asphalt and inorganic material,and at the micro level,asphalt and mineral powder(grain size is less than 0.075mm)form mortar structure material to bond and fill the gaps between aggregate particles,and to a large extent decide the mechanical strength and structural stability of asphalt mixture.But in traditional research,this micro mortar system was ignored because mineral powder was only looked as filler and more research were pay attention to asphalt binder and asphalt mixture.In this work,a series of rheological tests were put forward to evaluate the performance of asphalt and asphalt mortars,and some new evaluation methods were developed related to high temperature,low temperature and fatigue performance,and the behavior mechanism of asphalt and asphalt mortar in HMA were discussed to provide a newer thinking way to design and evaluate asphalt mixture pavement performance.The results showed that:Rheological methods research show that,strength,interface and loss factors can be obtained perfectly by dynamic shear rheometor(DSR)and these rheological parameters can be used to evaluate asphalt and mortar performance better.Such as dynamic yield stress,unrecoverable compliance representing non-deformability,normal force representing flow process,interface adhesion index representing concreteness and Cole-cole model analysis representing phase segregation and others.There are some differences between neat asphalt and modified asphalt by rheological evaluation.SBS modified asphalt structure recovery time is less than neat asphalt when load uninstall,thus modified asphalt can increase elastic recovery of asphalt mortar,but neat asphalt has no this property.At the same time,appropriate filler asphalt content can be decided by rheological test including multiple stress creep and recovery test,this scientific limitation of filler content can assure good high temperature and construction performance of asphalt mixture and guarantee an appropriate anti-fatigue and low temperature performance.Grey correlation analysis proved that rheological parameters have a better relation to mixture performance than traditional evaluation parameters.There are apparent difference between neat asphalt and SBS modified asphalt mortars,but all asphalt mortars have a same behavior when damaged in a lower temperature.In high temperature and low load frequency condition,mineral filler doesn't change viscoelasticity constitution and only upgrade modulus values for neat asphalt,but for SBS modified asphalt,mineral filler do change viscoelasticity constitution and modulus jointly.When temperature decreases until to some position,the interface adhesion index decreases and begin to have glass transition or interface crack when asphalt mortar complex modulus up to about 29 MPa.At the same time,mineral filler content has a stage influence characteristics on asphalt mortars,it can weaken interface adhesion ability with content increase when temperature below some position,on the contrary,it can improve adhesion ability when temperature above some position.As a general rule,higher mineral filler content can upgrade high temperature performance of asphalt mixture.As to asphalt mortars,their fundamental property relies on base asphalt,and its performance efficiency depends on the doped mineral filler,and different filler have different improvement effects.It is different in behavior mechnisam of mineral filler for neat asphalt and SBS modified asphalt.Meanwhile,neat asphalt has apparent fatigue initialization and extension characteristics in fatigue test,and modified asphalt has no this apparent phenomenon because of higher elasticity.Experiment show that mineral filler cannot improve mortar performance any more when mineral filler hydrophilic coefficient more than 1,and methylene blue value more than 12.Finally,from three levels of correlation among asphalt,mortar and mixture volume index,a series of grey relation analysis show that,asphalt mortar is an independent material system and its property parameter determine asphalt mixture performance than asphalt level in a larger extent.