Dense skeleton asphalt mixture materials are used in the construction of pavements and roads due to their strong anti-rutting performance. Its structure is characterized by coarse aggregate comprising of the main skeleton, fine aggregates, asphalt, and other admixtures that fill the voids of the main skeleton. Several approaches have been proposed to evaluate the skeleton structural characteristics of asphalt mixtures. Unfortunately, quantitative analysis of the main skeleton structure and its corresponding gradual behavior under loading have not been fully explored.
To this note, Dr. Liwan Shi, Dr. Xin Xiao, Dr. Xiao Qin from Foshan University together with Professor Duanyi Wang from South China University of Technology presented a mesoscale main skeleton structural system with medium contact chain for the analysis of meso-structural characteristics of asphalt mixtures. The system comprised of coarse aggregates, contact points, main skeleton, and contact chains. The structural stability of the main contact chain was analyzed theoretically while digital image processing was used to analyze: statistical characteristics of the main skeleton, contact chain, and gradual behavioral characteristics under loading conditions. Their main objective was to develop a meso-evaluation indices and criteria for designing a stable main skeleton and use as a reference for the design and gradation of dense skeleton asphalt mixture materials. The work is currently published in the research journal, Construction and Building Materials.
Results showed that the stability of the main skeleton was greatly influenced by the structural stability of the main contact chain. Consequently, the stability of the main contact chains was affected by sizes of the coarse aggregate particles, structure, length, cohesion of the asphalt binder, and the direction of the main contact chain. The material’s stiffness and resistance to deformation properties were enhanced by shorter contact chain, coarser gradation, and linearization of the main contact chain with the same loading direction. Furthermore, the stability of the main skeleton and the rutting resistance of the asphalt mixture, were enhanced by improving the gradation of the main skeleton and using asphalt with greater cohesive forces.
Loading action resulted in the movement of coarse aggregates, an increase in the length of the contact chain, and a decrease in the total number of the contact chain thus producing a more perfect skeleton. For asphalt mixture samples created by the wheel rolling method, it was worth noting that the design criteria of the main skeleton structure meso-index should exceed 80% for Ks and less than 37 for Nn. This ensures that the coarse aggregates make contact with each other to form the desirable skeleton.
In a nutshell, the study presented a mesoscale analysis of meso-structural characteristics of asphalt mixture. Factors affecting the stability of the main contact chain including length, structure, and particle size of the coarse aggregates were revealed. Also, longer contact chains and lower number of contact chains significantly contributed to the realization of the perfect main skeleton. In a statement to Advances in Engineering, Dr. Liwan Shi, first author stated that the presented design criteria ensure interlocking of the coarse aggregates and will be of great use in the design, development, and optimization of dense skeleton asphalt mixture for practical applications. In order to further research and application, they have developed the software for meso-structural characteristics analysis of asphalt mixture.
Shi, L., Wang, D., Xiao, X., & Qin, X. (2020). Meso-structural characteristics of asphalt mixture main skeleton based on meso-scale analysis. Construction and Building Materials, 232, 117263.