Study On Properties And Road Performance Of Calcium Sulfate Whisker And Straw Fiber Modified Asphalt

The diseases of asphalt pavement has become increasingly prominent with the increasing of traffic volume and vehicle load.Under the combined effect of load and environment,the pavement is prone to various forms of damage such as rutting,shoving,looseness,extensive oil,cracking etc.From the perspective of the asphalt mixture itself,improving the road performance has become hotspot for research.In this paper,calcium sulfate whisker and straw fiber composite modified asphalt was proposed.Calcium sulphate whisker and straw fiber were added as complex modifiers into the matrix asphalt and the technical properties of asphalt after composite modification and the road performance of asphalt mixture were studied.First,the basic technical properties of CSW phase and morphology were measured by XRD,SEM and routine laboratory analysis.The oil absorption,water absorption and thermal stability of straw fiber were tested.The results show that the selected CSW and the straw fiber could meet the basic requirements of the asphalt modifier.CSW modified asphalt was prepared by mechanical stirring method,and the technical indicator of it was tested.The results show that the penetration and elongation of 70 # asphalt and 90 # asphalt decreases in the range of 0-8 wt%,and the softening point increases,70 # asphalt PI increases from-1.3793 to-0.7834,│VTS│ from 1.4311 to 0.4139,90 # asphalt PI increases from-1.4773 to-0.8397,│VTS│ from 2.1341 has been reduced to 0.4434.The viscosity of asphalt,temperature stability and temperature sensitivity were improved by CSW,whereas the plasticity was reduced.CSW and straw fiber composite modified asphalt was prepared by mechanical stirring method,and the indicator of modified asphalt was texted.The results show that in the range of CSW 0-6wt% and straw fiber 0-0.5wt%,with increasing the content of modifier,asphalt penetration decreases,shear strength increases,10 ℃,15 ℃ ductility biggest drop of 61% and 40.5%,the softening point increased from 49.1 ℃ to 62.3 ℃,temperature sensitivity coefficient has been reduced from 0.0337 to 0.0279,│VTS│ has been reduced from 2.1339 to 0.3536.It can be seen that compound modification can improve the viscosity of asphalt,temperature stability and temperature sensitivity.Based on the RTFOT and PAV experiment,it was found that the aging resistance of asphalt can be improved by compound modifier.In this study,SAC-16 asphalt mixture was selected and the graded test of the quarried ore was carried out by VCADRF method.The proportion of the asphalt mixture was matched by Marshall method.The road performance of the composite modified asphalt mixture was further analyzed.Through the rutting test,it was found that the maximum stability of CSW and straw fiber composite modified asphalt mixture increased by 34%,and the rutting resistance was improved significantly;through the indirect tensile test,it was found that the maximum increase of splitting strength and stiffness modulus of composite modified asphalt mixture were 29%,40% and the low temperature crack resistance was improved in a certain dosage range(CSW0-4%,0-0.5% of the straw fiber);through the freeze-thaw splitting test,it was found that the TSR of the composite modified asphalt mixture was increased from 83.2% to 93.2% of the unmodified mixture and the water stability was also improved.In this paper,the influence of modifier on the performance of the mixture was evaluated by gray correlation analysis and the optimum blending ratio was chosen as 4% of CSW content and 0.5% of straw fiber content.