Microscopic Characteristics Of Polyurethane Modified Asphalt And Their Influence On The Properties Of Porous Mixtures

Faced with the problems of heavy traffic load and channelized traffic,it is necessary to find high-quality modified asphalt to cope with the requirements of the rapid development of traffic on the road surface.Polyurethane modified asphalt has good viscosity and toughness,but in previous studies,there were problems such as poor compatibility between solid polyurethane and asphalt,and excessive consumption of modifiers for polyurethane modified asphalt,so this paper studied it in detail.In this paper,polyurethane prepolymer(polyether type)modified with 90# matrix asphalt modified under 0%～12% content was used as the research object,and SBS modified asphalt was added for comparative analysis.Firstly,based on molecular dynamics and relying on Materials Studio software,the compatibility,mechanical properties and molecular structure of polyurethane modified asphalt were studied.The modification mechanism of polyurethane modified asphalt was analyzed by Fourier transform infrared spectroscopy(FTIR)test.Secondly,the high and low temperature properties of polyurethane modified asphalt were studied by dynamic shear rheological test(DSR)and bending beam rheological test(BBR).Finally,the road performance of polyurethane modified porous asphalt mixture graded with PAC-13 type was studied by high temperature rutting test,low temperature trabecular test,freeze-thaw splitting test and water-immersion Marshall test.At the same time,the water seepage test and standing wave tube test were designed,and the drainage performance and noise reduction performance were studied,aiming to study the functional characteristics of polyurethane modified porous asphalt mixture.In the results of polyurethane modified asphalt,the results of microscopic simulation show that the internal system almost reaches a stable state when the molecular dynamics simulation is carried out at 200 ps,and when only considering the influence of temperature,the compatibility between polyurethane molecules and asphalt molecules at 413K(140°C)is better,and the micromechanical properties of modified asphalt decrease with the increase of temperature,but the performance is still significantly better than matrix asphalt.New characteristic peaks appear in the test results of polyurethane-modified asphalt infrared spectroscopy,indicating a chemical reaction between polyurethane and asphalt.The results of DSR and BBR test show that the addition of polyurethane can significantly improve the rheological properties of matrix asphalt,and the more polyurethane content,the better the high temperature performance and low temperature performance of polyurethane modified asphalt.The performance comparison results of polyurethane modified asphalt and SBS modified asphalt show that the high and low temperature performance of polyurethane modified asphalt under the best dosage is better than that of SBS modified asphalt.The results of polyurethane modified porous asphalt mixture showed that polyurethane modified porous asphalt mixture had good high temperature stability and low temperature crack resistance compared with matrix asphalt mixture,and was stronger than SBS modified porous asphalt mixture.Its water stability is improved compared to matrix asphalt mixtures,but slightly inferior to SBS modified porous asphalt mixtures.By comparing and analyzing the specimens graded with PAC-16 and PAC-13,the addition of polyurethane improved the drainage performance of porous asphalt mixture.Polyurethane modified porous asphalt mixture achieves the best sound absorption at 630 Hz.