نمونه متن انگلیسی مقاله
The objective of this study is to investigate the micro-mechanical characteristics of High Modulus Asphalt Concrete (HMAC) pavement structure under loads. The Discrete Element Method (DEM) was employed in this study to build the models for HMAC pavement and conventional asphalt pavement structures. The laboratory tests and DEM simulations of uniaxial compression tests were conducted on the materials of HMAC pavement structure layers. To simulate the mechanical behavior of the asphalt mixture, micro-parameters were adjusted to fit with the strain–stress curve results from lab-test. The displacement and stress distribution in vertical and horizontal directions, and the shear stress in the horizontal direction were analyzed for the HMAC pavement and conventional asphalt pavement. The results showed that the maximum vertical displacement of HMAC pavement (0.25–۰٫۲۹۳ mm) was less than that of the conventional asphalt pavement (0.3–۰٫۳۲۴ mm). The application of HMAC decreased the vertical stress in all structural layers except the upper surface layer. The HMAC decreased the horizontal stress in the subbase layer. Though the HMAC pavement had a slightly greater horizontal shear stress in the upper and middle surface layers than the conventional asphalt pavement, its shear resistance was. Therefore, the results indicated HMAC layer can enhance the resistance to deformation and reduce the rutting potential in asphalt pavement.
High-modulus asphalt concrete (HMAC) was originated from France in 1980s to increase the rutting mitigation resistance and the stiffness of asphalt base layers . Generally, there are three methods to obtained high modulus binders which contributes the most of the higher stiffness of HMAC: use hard-grade asphalt binders that have low penetration and high softening points ; use polymer modifier, such as SBS and lake asphalt [3–۵]; use high-modulus agent [3,6,7]. HMAC shows evident higher stiffness when compared with conventional asphalt concrete. Pavements with HMAC base layers were reported to have good resistance to rutting and fatigue with the context of climate in France . By applying HMAC, the thickness of the base layer can be greatly reduced while the performance remains the same. However, researchers still have great concerns on the mechanical performance of the HMAC in more inclement climate condition, especially its low temperature performance. Researchers from Spain carried out the repetitive loading axial tests at high temperature (40–۴۵ C) and found the permanent deformation resistance of HMAC was highly related with the asphalt grade and voids contents [2,7].