Analysis On The Influence Of Different Factors On The Shear Performance Of Asphalt Mixture

Asphalt pavement is the most common type of pavement for domestic high-grade highway.Rutting and crack appear often too early because of the extreme climate and heavy traffic load.Among them,there is a direct correlation between the flow rutting and top-down cracks and the shear performance of asphalt mixture.Therefore,It is of great practical significance to prevent the early disease of asphalt pavement to choose a suitable method to measure the shear strength of asphalt mixture and study the influencing factors of shear strength.Based on a large number of domestic and foreign literature research on the shear test method and influence factor of shear strength of asphalt mixture,the test of ring shear and uniaxial penetration was used to determine the shear strength of asphalt mixture.First,the effect of experimental condition,such as Temperature and load speed,is studied on the shear strength of mixed material.The results showed that:(1)The higher the temperature,the lower the shear strength of the mixture;the higher the loading rate,the higher the shear strength of the mixture.(2)Anti-rutting agent has obvious effect on improving the cohesion of the mixture,while the influence on inner friction angle is very limited;and the best dosage of anti-rutting agent is 3‰.In addition,the effect of material composition which contain Asphalt,mineral materials,packing was studied on the shear resistance of mixed material,and the experimental results showed that:(1)Compared with 70#asphalt,SBS modified asphalt is mainly to improve the cohesion of the mixture,while have limited effect on the internal friction angle;and there is no obvious correlation between the penetration and ductility index and mixture shear strength;The higher the softening point,the better the shear performance of the mixture,but there is no a significant linear relationship.(2)The asphalt content has a significant influence on the cohesion of the mixture,but has little effect on the internal friction angle.The best oil stone ratio determined by shear test is smaller than that of Marshall test.Therefore,it is suggested that OAC is higher than that in the high temperature and heavy traffic section.(3)The shear strength of SMA grading is better than the AC gradation when the maximum nominal particle size is the same.The bigger the nominal particle size,the greater the shear strength of the mixture.But one-sided increase the content of coarse aggregate does not necessarily increase the shear strength of the mixture.(4)The best dosage of cement and phosphorus slag instead of mineral powder were respectively 20%and 10%.Finally,the factors that the aggregate is contaminated with mud were studied on the shear performance of the mixed materials.The results showed that:the bigger the clay content of the aggregate,the worse the shear performance.Influence of fine aggregate containing clay on shear strength of mixture is greater than that of coarse aggregate.