Analysis Of The Influence Of Polyurethane Aggregate Ratio On Stone Mastic Polyurethane Performance And Establishment Of Prediction Model

Stone Mastic Polyurethane(SMP)is a new pavement material which completely replaces asphalt with polyurethane as adhesive and has better pavement performance than asphalt mixture.Through previous studies,the our team found that SMP was still far superior to the performance of asphalt mixture under the condition of lower than the optimal polyurethane aggregate ratio.Therefore,in order to reduce the cost and meet the technical requirements of different projects,this paper adopts different polyurethane aggregate ratio to analyze and study the performance variation rules of SMP.The prediction model between polyurethane aggregate ratio and road performance was established.And the durability of SMP is evaluated,which lays a foundation for the popularization and application of the material.Firstly,basis stone mastic asphalt-13(SMA-13)graduation prepared SMP.The optimal polyurethane aggregate ratio is 7.5%by using Marshall design method.All the road performance can meet the design requirements.Secondly,the minimum polyurethane aggregate ratio is 5.0%by observing the mixing state.In order to study the effect of polyurethane aggregate ratio on SMP performance and establish a performance prediction model,SMP with polyurethane aggregate ratio of 5.0%,6.0%,7.0%,7.5%were selected as test objects.The porosity,film thickness,high-temperature performance,low-temperature performance and water stability of SMP at the selected polyurethane aggregate ratio were tested.Analyzed the impact of polyurethane aggregate ratio on the performance of the SMP.The test results show that the road performance of SMP decreases with the decrease of polyurethane aggregate ratio.The dynamic stability,bending strain at low temperature,splitting tensile strength before and after freezing-thawing decrease by 62.9%,65.2%,19.0%,45.4%,when the polyurethane aggregate ratio decreases from 7.5%to 5.0%.Based on the grey prediction model,the prediction model of road performance of SMP with different polyurethane aggregate ratio was established,and the fitting accuracy of model was high(R~2>0.99).Thirdly,the durability against water damage and Uv aging of SMP with the selected polyurethane aggregate ratio was studied.In terms of durability against water damage,the residual splitting strength of SMP after several freezing-thawing cycles was tested,and the fracture surface of the specimen was scanned by SEM.In terms of durability against Uv aging,the residual splitting strength of SMP after different aging days was tested and its apparent state was observed.The test results show that the splitting strength of SMP decreases with the decrease of polyurethane aggregate ratio and gradually becomes stable.After several freezing-thawing cycles,the interior of SMP specimens was damaged by water frost heave,and the voidage increased gradually.Under long-term Uv irradiation,the adhesion of some adhesives on the specimen surface decreased and it fell off from the specimen surface.Based on the Verhulst biological model,the prediction model of residual splitting strength of SMP in aging process with different polyurethane aggregate ratio was established,and the fitting accuracy of model was high(R~2>0.99).Finally,the durability against load of SMP with the selected polyurethane aggregate ratio was studied.Through MMLS3 accelerated loading test,the splitting strength of SMP before and after loading under different polyurethane aggregate ratio was compared.The strength loss rate of SMP is less than 4%,indicating that it has good durability against load.The strength loss rate of SMP before and after loading increases with the decrease of polyurethane aggregate ratio.Polyurethane aggregate ratio decreased from 7.5%to 5.0%,and the strength loss rate increased by 3.2%.