Study On Performance Of Asphalt Mortar And Framework Structured Asphalt Mixture Based On Meso-mechanics

With the rapid growth of traffic and overload, the early diseases of asphalt pavement are increasing, which results in that the actual life of pavement was significantly lower than the design life. To date, the prediction and determination of the bulk behavior of AC is largely based on experiments as well as experience, and it is often time-consuming and cannot reflect the influence of the micromechanics behavior of AC. Therefore, it is necessary to acquire more insight into asphalt mortar, the interface between asphalt mortar and framework grain, and the characteristic parameters of asphalt mixture gradation from the mesoscopic level, thus to construct the analytical theories system of damage mechanical behavior of asphalt pavement materials, and to provide more reliable technical foundation and theoretical basis for the design, construction and the maintenance of asphalt pavement materials.This paper takes meso-mechanical characteristics of asphalt mixture as the guideline. Firstly, stress-strain compression tests and shear tests were conducted on asphalt mortars of different materials and gradations, thereby analyzing the mechanical properties of asphalt mortars under different conditions. Based on the results of the above tests, cohesive zone model was built to simulate the meso damage mechanic characteristics of the interface between asphalt mortar and framework grain, and with which the meso damage mechanic characteristicsof asphalt mortars were analysed theoretically as a comparison. Secondly, dominant structure contact percentage(cnDS) was regarded as the starting point. In order to analyze their association between the dominant structure parameter and the performance of asphlat mixture, the pavement performance test, the mechanical performance test and the fatigue performance test of different gradations aphalt mixtures were conducted. And based on the combination of the four-point bending fatigue test and digital image correlation(DIC), the fatigue damage meso-mechanism of alphalt mixtures were studied, while the quantitative analysis of fatigue damage characteristics of the different gradation asphalt mixturewere conducted. Finally, based on the research results, this paper puts forward a mix optimization design method of the framework structured asphalt mixturefor the durability. The main innovative works completed in this paper are:(1) To analyze mechanical properties of mortar, the different proportions, the asphalt base material and the condition of freezing and thawing were selected as influencing factors. The results indicate that the appropriate proportion can improve the cohesion of mortar and enhance its mechanical durability. Besides, the mortar with admixture and rubber asphalt has higher stiffness, anti-deforming capability and water stability.(2) Based on the processing results of cohesive zone model of meso-mechanics damage, KS mortar has smaller damage fields than normal mortar, while its strength degradation degree is significantly decreased. In the meantime, freezing and thawing mortar has larger damage fields than normal mortar, while its strength degradation degree is significantly increased.(3) The experimental results indicate that cnDS increases with the amount increasing of dynamic stability. Moreover, the calculated value of shear strength and the anti-fatigue performance increases initially and then decreases with the increase of cnDS.(4) Referring to the results of grey relation analysis, cnDS has the best correlation with the high temperature stability, shear strength and the anti-fatigue performance in the seven different parameters. The experimental results show that the three kinds of performance are all good, when the value of cnDS ranges from 11.0% to 13.6%.(5) Based on the combination of the four-point bending fatigue test and digital image correlation(DIC), it is proposed that fatigue damage factors can quantitatively evaluate the meso-damage state of mixture,and translation angle and rotation angle of framework grain help to increase the stability of framework structure at mesoscopic level. The calculation result of quantitative parameters shows that the value of cnDS is in a reasonable range; the mixture can be the stability of mesoscopic structure and have the better anti-fatigue performance, while the reliability of cnDS was checked at mesoscopic level.(6) Based on the value of cnDS, it is presented that parameter values can determine the state of the mesoscopic fatigue damage of mixture. For the different node of damage evaluation, fatigue damage factor should not be greater than 0.08, 0.25 and 0.42, respectively, while the weighted average of θ and α should not be greater than 60° and 0.11°.(7) After comprehension of above achievements, the author put forward a mix optimization design method of the framework structured asphalt mixturefor the durability. Key word:Framework structured asphalt mixture, Micromechanics, Asphalt mortar, FEM,...