Study On Toughness Modification Of Waterborne Epoxy Emulsified Asphalt Applicable To Plateau Zone

Waterborne epoxy resin has excellent properties as a thermosetting material,which provides waterborne epoxy emulsified asphalt（w-EA）materials with high strength and outstanding high-temperature performance.However,the poor toughness and low-temperature crack resistance of waterborne epoxy resin after curing limit the use of w-EA in plateau zone.In order to solve the high brittleness and poor performance at low-temperature of w-EA,waterborne polyurethane（w-PU）is used as a toughening agent to modify waterborne epoxy emulsified asphalt（w-PUEA）.Investigate the effect of adding w-PU on the microstructure and properties of w-PUEA;study the impact of w-PU on the performance of w-EA mixtures;attempt to explore the road performance of emulsified asphalt and modified emulsified asphalt mixtures under maintenance in high-altitude environments to expand the application of w-EA in plateau zone.Firstly,the amount of suitable waterborne epoxy resin for toughening modification is selected based on the microstructure and mechanical properties of w-EA.On the basis of 20%w-EA,different amounts of w-PU are selected for toughening modification of w-EA.The creep resistance,low-temperature performance,tensile mechanical properties,and microstructure of both w-EA and w-PUEA are studied in this paper.The addition of w-PU can significantly improve the long-term creep behavior of w-EA.The results from low-temperature stress relaxation tests show that the relaxation rate of 10%w-PUEA(0.27MPa·s^-1)is 1.93 times higher than that of w-EA(0.14 MPa·s^-1).The flexible w-PU can improve the elongation at break（124%）and toughness（179 MJ/m³）of 10%w-PUEA by300%and 171%,respectively,in comparison with w-EA（31%and 66 MJ/m³）.In addition,as the amount of w-PU is increased,the resin network structure in w-PUEA becomes more complex.At the same time,the micro-CT results show that the asphalt phase in the 10%w-PUEA system presents small and uniformly dispersed particles.Secondly,the effect of adding 10%w-PU on the road performance of w-EA mixture is investigated and compared with the performance of w-EA mixture and emulsified asphalt mixture.The research finds that the Marshall stability,high-temperature performance,and water stability of the 10%w-PUEA mixture all exceed the standard requirements.Furthermore,the anti-bending tensile strain of 10%w-PUEA mixture（2703με）increases by44.62%compared with w-EA mixture（1869με）,indicating that the addition of w-PU can significantly improve the low-temperature crack resistance of w-EA mixture.Finally,the study collects and reviews climate data of the Tibetan Plateau and references the characteristics of the climate data to create a plateau environmental simulation box.The study determines the parameters for simulating the plateau environment.The temperature inside the maintenance box is 50°C,the wind speed is 5 m/s,and the simulated altitude in the maintenance box is 3650 m.The both emulsified asphalt and modified emulsified asphalt mixtures are maintained in a plateau environment simulation box.The road performance of the mixtures is tested after the completion of maintenance.The results indicate that the road performance of emulsified asphalt and modified emulsified asphalt mixtures is better than that of mixtures kept in a 60℃single-factor plain environment.