In asphalt mixture, aggregates account for up to 90% of the total volume and play an important role in the mechanical characteristics of asphalt mixture. The proportions of fine and coarse aggregates in gradation, as well as the function of aggregate particles, are important factors for the skeleton structure performance of asphalt mixtures. However, the existing asphalt mixture design methods are mostly based on empirical methods, where the non-uniformity and complexity of the composition of asphalt mixtures are not fully studied. In this study, the skeleton structure of aggregate mixture and function of aggregate are studied and analyzed using the Discrete Element Method (DEM). The Particle Flow 3D (PFC3D) DEM program is used to perform the numerical simulation. The average contact number and interaction forces by aggregate particles of different sizes are obtained and studied. The skeleton structure of aggregate mixture and function of aggregate particles are further analyzed from the meso-structural perspective.

In the past decades, a large amount of research was conducted to investigate the application prospect of microwave heating technology in improving the efficiency of asphalt pavement self-healing and de-icing. This paper reviewed the achievements in this area. Firstly, the properties of asphalt concrete after microwave heating were summarized, including microwave sensitivity and heating uniformity. Then, the evaluation indicators and influence factors of the self-healing properties of the asphalt mixtures heated by microwave were reviewed. Finally, the application of microwave heating in asphalt pavement de-icing was explored. In addition, asphalt pavement aging due to microwave heating was also reviewed. It was found that microwave heating technology has good prospects in promoting asphalt pavement self-healing and de-icing. There are also some problems that should be studied in depth, such as the cost-effectiveness of microwave-sensitive additives (MSAs), the performance of the pavement with MSAs, mechanism-based self-healing performance indicators, and the aging of asphalt pavements under cycling microwave heating.

This paper presents an investigation on the influences of clay brick particles on the performance of cement stabilized recycled aggregate as pavement base. The comparative tests of unconfined compressive strength, compressive modulus of resilience, frost resistance, scouring resistance, drying shrinkage and temperature shrinkage of 6 kinds of mixtures with different coarse and fine clay brick particle contents were carried out. Test results showed that the unconfined compressive strength of cement stabilized recycled aggregate was compromised by the clay brick particles, especially the lateral strength. The coarse clay brick particles had little influence on the compressive resilience modulus of the mixture, while the fine clay brick particles could significantly increase it. The frost resistance of the mixture increased first and then slightly decreased with the increase of the content of coarse clay brick particle, while it increased with the increase of fine particle content. The scoured mass loss increased with the increase of coarse clay brick particle content. However, it is discovered that the fine clay brick particles had almost no influences on the scoured mass loss. The addition of both coarse and fine clay brick particles could decrease the drying shrinkage of the mixture at early construction stage. The temperature shrinkage performance of the mixture was not so sensitive to the addition of clay brick particles. Generally, the cement stabilized recycled aggregate with clay brick particles could meet the requirements of the pavement base in many cases but it needs to be optimized in application with consideration of the load and climate conditions.

Surface texture is a very important factor affecting the anti-skid performance ofpavements. In this paper, entropy theory is introduced to study the decay behavior of thethree-dimensional macrotexture and microtexture of road surfaces in service based on the field testdata collected over more than 2 years. Entropy is found to be feasible for evaluating thethree-dimensional macrotexture and microtexture of an asphalt pavement surface. The complexityof the texture increases with the increase of entropy. Under the polishing action of the vehicle load,the entropy of the surface texture decreases gradually. The three-dimensional macrotexture decaycharacteristics of asphalt pavement surfaces are significantly different for different mixturedesigns. The macrotexture decay performance of asphalt pavement can be improved by designingappropriate mixtures. Compared with the traditional macrotexture parameter Mean Texture Depth(MTD) index, entropy contains more physical information and has a better correlation with thepavement anti-skid performance index. It has significant advantages in describing the relationshipbetween macrotexture characteristics and the anti-skid performance of asphalt pavement.

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