Semiflexible mixture is a composite paving material combining the advantages of both asphalt and cement concrete materials. It consists of matrix asphalt skeleton and cement mortar. Due to the different volume characters between asphalt structure and cement mortar, stress concentration always happens in this semiflexible mixture, leading to internal cracking. The objective of this study is to alleviate the internal cracking concern of the semiflexible mixture by adjusting the material components. To this end, optimal material design and numerical simulation have been conducted. Matrix asphalt structures with four different air voids were incorporated with different dosages of cement mortar. The contraction strain and expansion strain of cement mortar as well as the indirect tensile strength of matrix asphalt structure were measured. The results were input into ABAQUS for numerical simulation. The results indicated that (1) the internal stress in this semiflexible mixture is mainly determined by the contraction of cement mortar, rather than expansion; (2) larger air void of matrix asphalt structure and less volumetric variation of cement mortar reduce the internal stress; (3) once the air void of matrix asphalt structure is decided, both maximum contraction and expansion deformations of cement mortar should meet specific requirement to ensure less internal cracking. This is a practical-ready paper that provides reference for the anticracking design of semiflexible pavement.

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In recent years, preventive maintenance has been used widely to solve the problem of early-stage asphalt pavement damage. However, conventional preventive maintenance treatments cannot effectively prevent rutting or damage resulting from the leakage of diesel fuel to the pavement. In this context, numerical simulations of uniaxial penetration tests were conducted with the Discrete Element Model to evaluate the feasibility and effectiveness of pavement surface solidification with a special seal coat. Standard viscosity tests on mixtures of waterborne epoxy resin and emulsified asphalt used as the Permeating and Solidifying Seal Coat (PSSC) material were performed, and uniaxial penetration tests and accelerated loading tests were conducted on asphalt mixture specimens with and without the PSSC. The optimum proportion of PSSC material was determined and its permeability, rutting resistance, diesel fuel corrosion resistance, and durability were evaluated. The results of this study indicate that the superficially solidified pavement with PSSC can effectively enhance rutting resistance and diesel fuel corrosion resistance and can provide more durable skid resistance and better antistripping performance than conventional preventive maintenance treatments. Therefore, the PSSC could be considered a new generation of preventive maintenance treatments for asphalt pavements.

At present, research on the internal structures of asphalt mixtures has mostly focused on the statistical analysis of their mesostructural components such as aggregates, voids, and asphalt mortars, in addition to the verification of the mechanical behaviour of the mixture through simulations. Furthermore, the capacity of the research has not risen to a level where a design method to guide the design and optimisation of the asphalt mixture gradation has been formulated. After an in-depth analysis of the existing evaluation parameters and standards for the asphalt mixture skeleton, this study proposes a new method for precise designing a dense skeleton asphalt mixture (DSAM) based on meso parameter. e results indicate that the application of digital image processing (DIP) techniques to adjust the gradation increases the average coordination number (n c ) and reduces the ratio of the quantity of coarse aggregate without contact point to the total quantity of coarse aggregate (C value). is can effectively improve the meso parameters of the mixture so that the quality of the main skeleton is significantly enhanced; the process also has higher precision and demands less test work. VCA mix (IMAGE) ≤ VCA DRC and n c >1.6 while C < 20% can be used as qualitative and quantitative evaluation criterion for forming better main skeleton structure of coarse aggregate. e new method of designing a DSAM based on meso parameter is intuitive and convenient, which considerably reduces the blindness and tediousness in the design of the asphalt mixture gradation. e engineering example also proves that the asphalt mixture has an excellent pavement performance and verifies the feasibility of the proposed design method.

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