Effect Of Coarse Aggregate On High And Low Temperature Performance Of Asphalt Concrete

With the continuous increase of highway mileage in China,the road performance of asphalt mixture is increasingly required by highway engineering.Coarse aggregate not only determines the skeleton structure type of asphalt mixture,but also directly affects the mechanical properties of the mixture.Therefore,it is of great significance to study the influence of coarse aggregate on the performance of asphalt mixture to improve the road performance of asphalt mixture.Therefore,the influence of coarse aggregate morphology on high temperature viscoelasticity and low temperature crack resistance of asphalt mixture was studied.Firstly,this paper presents a morphological characterization method of aggregate based on digital image technology and tests the morphological characteristics of three kinds of aggregate with different particle sizes.On this basis,this paper carried out coarse aggregate morphology design and used to produce different morphological characteristics of coarse aggregate composition of asphalt mixture specimens.After that,high temperature uniaxial compression test,high temperature uniaxial creep test,low temperature trabecular bending strength test and low temperature trabecular creep test were carried out in this paper.Based on the test results,the influence law of coarse aggregate morphology on high temperature viscoelasticity and low temperature crack resistance of asphalt mixture was analyzed.Finally,according to the influence law,the paper puts forward the optimized scheme of morphology index of coarse aggregate with high and low temperature balance.The results show that the morphological analysis method of coarse aggregate based on digital image can accurately reflect the pinprick index,angular index and texture index of aggregate.Scanning electron microscopy showed that the surface texture of basalt and andesite was rougher,which made the corrosion expansion area of basalt and andesite larger than that of pebbles.Uniaxial creep test results show that coarse aggregate angularity has an effect on the creep performance of asphalt concrete.With the increase of the pebble content in the asphalt mixture,the creep of the mixture increases at the same temperature and under the same condition.The bending creep test results of low-temperature trabecular beams show that with the increase of coarse aggregate angularity,the low-temperature bending resistance of asphalt concrete decreases,that is,the brittleness of asphalt mixture increases.Balance of high and low temperature performance of coarse aggregate index optimization results indicate that using compression fracture strength,creep delay time and changing rate of stress relaxation modulus and flexural failure of four high and low temperature related control indexes aggregate angularity can control to a certain extent to ensure high temperature rutting resistance of asphalt mixture and the low temperature crack resistance.