Research On Rheological Characteristic Of Polyphosphoric Acid Modified Asphalt Motar

According to modern mortar theory,the asphalt mortar,rather than asphalt alone,play an important role of binding aggregate in asphalt mixture.Polyphosphoric acid(PPA)can significantly increase the performances of asphalt mixture through improving asphalt binder.Therefore,it is necessary to explore the rheological characteristical of PPA modified asphalt motar.In this study,the rheological character-ristical of PPA modified asphalt motar was studied by using DSR and BBR.The main results obtained are as follows:(1)Instrument parameters of DSR:The change of strain levels(?)has effect on the high temperature properties of PPA modified asphalt motar,but it is not significant.The rutting parameter(G*/sin?)of PPA modified asphalt motar increased with the increase of?.Under different experiment conditions,G*/sin? of different mortar are tested.It is found thatG*/sin?increases exponentially with the increase of the ratio of filler to bitumen and decreases with the increases of temperature.Under the same experiment conditions,PPA modified asphalt motar with different filler type have different G*/sin ? and the order is:hydrated lime>mineral powder>cement.Moreover,in the research of high temperature performance,the optimal the ratio of filler to bitumen was 0.9 to 1.2(for PPA modified asphalt motar with hydrated lime)and 1.2 to 1.5(for PPA modified asphalt motar with mineral powder or cement).(2)Under the same experiment conditions,the fatigue parameter(G*sin?)of PPA modified asphalt motar decreased with the increase of y and temperature,and increased with the increase of co and ratio of filler to bitumen.Under the same temperature,when the ratio of filler to bitumen is low,the PPA modified asphalt motar with cement has the best ability to resist fatigue damage,when the ratio of filler to bitumen is high;the PPA modified asphalt motar with mineral powder has the best ability to resist fatigue damage.(3)Under the same ratio of filler to bitumen,with the decrease of temperature,the creep stiffness(S)of PPA modified asphalt motar was increased and m-value was decreased.Under the same temperature and filler type,the creep stiffness(S)of PPA modified asphalt motar was increased with the increase of ratio of filler to bitumen,but the ratio of filler to bitumen has little effect on the m-value of PPA modified asphalt motar.