Study On Low Temperature Performance Of Plant-mixed Heat Recycled Asphalt Mixture

This paper established the evaluation system based on the cold region,selected the beam experiment and freeze-thaw cycle to evaluate the roads in frozen areas,made a comprehensive analysis of the various parameters on the low temperature performance,and improved the low temperature performance in aspects of mix proportion.The the coarse and fine gradation was separately designed by the trigonometric coordinate method,the recommended range of VV and VMA were given.Finally,the effectiveness of the design method was proved by the performance test.Specifically:Firstly,the new evaluation system was established.By comparing nine kinds of mechanism tests,and based on the temperature conditions in different regions and disease mechanism,some good tests were selected.Then,combined with the experimental difficulty,simulation mechanism,evaluation of consistency,discrimination of mixture of different types of data variability,correlation,the energy got in the beam test and freeze-thaw cycle was selected to evaluate the low temperature performance.It was proved that freeze-thaw cycles aggravated the influence of old asphalt,and can effectively simulate long-term performance of mixture,also the coefficient of bending was rase to define failure state and predict fracture temperature.Secondly,the effect of different parameters on the performance of regenerated material was discussed.It was demonstrated that the amount of RAP,the gradation,the ratio of oil,the type of asphalt and the degree of aging have a significant influence on the fracture energy and the fracture energy ratio.For thr resistance of low temperature:gradation>RAP>oil stone ratio,for the frost resistance:gradation>oil stone ratio>RAP.In addition,in order to ensure the performance and variability,the recommended rate of RAP was less than 30%,the asphalt aggregate ratio should also be increased appropriately,the rate of 4.75mm was recommended to be more than 45%,rubber asphalt was a good material to improve significantly.Meanwhile,the asphalt penetration was associated with the performance.Thirdly,the design method of asphalt mixture based on low temperature performance was established.Through the analysis of variance,for the aggregate less than<4.75mm,the rate of 1.18mm and 0.075mm were controled by triangle coordinate method,aimming at getting the low porosity and the low surface area;for the aggregate more than<4.75mm,the step filling method was used.For the proportion of the coarse and fine parts,the performance variability was considered.Then,the proportion of 1:1 was selected considering the high and low temperature performance and the coefficient of variability.For the best oil ratio,the high and low temperature performance was controlled by revising the Marshall volume parameter.Through the analysis of variance,it was found that VV has a significant effect on high and low temperature performance,and VMA has a significant influence on the high temperature performance.By changing the ratio of oil to change VV,and control the low temperature performance.Meanwhile,the high temperature performance can reach two times of the standard.By changing the ratio of oil and compaction degree to ensure VV unchanged,and VMA changed.The upper limit of VMA was controlled to ensure the high temperature performance reaches 2000/mm.Meanwhile,the lower VMA limit ensures the minimum asphalt film thickness of 7.The revised Marshall volume parameters were obtained as follows.The performance verification showed that the design scheme is effective:with 35%RAP,the low temperature performance was 27%higher,the high temperature performance was increased by 25%,and the embrittlement temperature was reduced by 2 degrees.At last,the scheme to increase the construction compacting aimming at reducing the oil ratio and improving theperformance was put forward,then,the compaction effect of different parameters of mixture was discussed,and the use of gyratory compaction instrument to create recycled asphalt mixture specimens was recommended.The recommended standards for the compaction work based on the rutting board are as follows:(?)...