Study On Road Performance And Numerical Simulation Of Cold Recycled Mixture Under Freeze-thaw Cycle

Asphalt mixture recycling technology provides an effective solution for the utilization and management of road waste materials.It has good economic,social and environmental benefits.It has been widely used in our country’s high-grade highway base,ordinary highway surface and base,etc.Asphalt pavements in Northwest our country,North China,and Northeast China are greatly affected by frost damage.Asphalt pavements in such seasonally frozen areas not only need to withstand varying degrees of vehicle load during service,but also need to withstand more complex environmental effects.The effect of freeze-thaw cycle makes the emulsified asphalt cold regenerated pavement prematurely damaged,shortens the service life of the pavement and affects the performance of the road.At the same time,it also increases the construction and maintenance costs of the pavement throughout its life cycle.In view of this,this research carried out the road performance and numerical simulation research of the emulsified asphalt cold recycled mixture under freeze-thaw cycle conditions.The main research contents and results are as follows:1.The temperature sensor is embedded in the cold recycled mixture sample to determine the freeze-thaw cycle test conditions;uniaxial penetration strength test,low-temperature split strength test and freeze-thaw split test are selected to study cold regeneration mixing under freeze-thaw cycles road performance of the material.The results show that the freeze-thaw cycle has an obvious negative effect on the high-temperature stability,low-temperature crack resistance and water stability of emulsified asphalt cold recycled mixture.After 20 freeze-thaw cycles,the cumulative penetration strength loss rate of the cold recycled mixture reached59.42%,the cumulative low-temperature splitting strength loss rate reached 56.37%,the cumulative freeze-thaw splitting strength loss rate reached 29.38%,and the TSR reached73.7%.,lower than the requirement of 75% of the specification value.2.Carry out the ultrasonic velocity test on the cold regenerated mixture sample after the freeze-thaw cycle,modify the test result through the correction time formula,and establish the correlation between ultrasonic velocity and high temperature stability,low temperature crack resistance and water stability,so as to achieve the purpose of using the ultrasonic velocity to predict the performance of the cold regenerated mixture.The results show that the effect of the freeze-thaw cycle significantly reduces the ultrasonic velocity of the specimen,and the ultrasonic velocity decreases by 3% to 6% every 5 freeze-thaw cycles.The ultrasonic velocity corrected by the correction time formula has a good correlation with the road performance of the cold regenerated mixture,and the prediction error is basically kept below 6%.Therefore,the ultrasonic method is feasible to predict the road performance of cold recycled mixture.3.According to the results of the road performance test,first carry out the simulation of the temperature field of the cold recycled mixture under the action of the freeze-thaw cycle to initially verify the feasibility and accuracy of the ABAQUS simulation of the freeze-thaw cycle,and then carry out the numerical simulation of the uniaxial penetration strength test and numerical simulation of low temperature split test.The results show that the internal temperature change of the mixture sample is a gradually changing process from the outside to the inside during the freeze-thaw cycle.At the same time,there is a certain temperature difference between the inside and outside of the specimen.The temperature field simulation results are consistent with the measured temperature change.The internal stress state of the mixture specimen in the numerical simulation of the uniaxial penetration strength test and the low-temperature splitting test conforms to the actual test conditions,and the simulation errors are within the range of 1.53%～2.99% and 7.83%～13.90%,so the simulation results Has a certain degree of accuracy and reliability.