Rui Wang’s research while affiliated with Minzu University of China and other places

Nano-clay has the potential to improve the properties of cement-based materials. However, the effectiveness of this improvement is influenced by the dispersion of the nano-clay. The effects of different nano-clay dispersion techniques on cement-based material properties and pore structure complexity were studied. The samples were prepared using manual and mechanical dispersion methods. The mechanical properties of the specimens were evaluated, and the pore characteristics of the cement-based materials were analysed using mercury intrusion porosimetry. The study investigated the effect of the dispersion method on the nano-clay dispersion. The complexity of the pore structure was evaluated using a fractal model, and the relationship between the fractal dimension, mechanical properties, and pore structure was analysed. The findings indicate that mechanical dispersion results in better dispersion than manual dispersion, and the mechanical properties of mechanical dispersion are superior to those of manual dispersion. Nano-clay particles can improve the internal pore structure of cement materials. Through mathematical calculation, the surface fractal dimension is between 2.90 and 2.95, with good fractal characteristics. There is a good correlation between the surface fractal dimension and the mechanical properties. The addition of nano-clay can reduce the complexity of the pore structure, and the fractal dimension has an excellent linear relationship with the pore structure.

In this paper, harmless municipal solid waste incineration fly ash (H-MSWIFA) was used to replace part of the mineral powder in asphalt mastic prepared with different ratios of filler to asphalt (F/A). Cone penetration (CPT), rotational viscosity, low-temperature bending, and full section fracture energy(FSFET) tests on the prepared H-MSWIFA asphalt mastic were carried out to evaluate the viscosity at room temperature, viscosity at high temperature, tensile property at low temperature, and crack resistance at room temperature of the asphalt mastic with different F/A and different H-MSWIFA content. An asphalt concrete mixture with a nominal maximum particle size of 13 mm (AC-13) with different F/A and H-MSWIFA replacement ratios was prepared. The effects of F/A and H-MSWIFA content on the high-temperature stability, water stability, and low-temperature cracking resistance of the asphalt mixture were studied. The results showed that the shear strength and viscosity of the asphalt mastic increased after H-MSWIFA replaced part of the mineral powder; and the greater the F/A, the greater the shear strength and viscosity of the asphalt mastic. H-MSWIFA can greatly improve the viscosity of asphalt mastic at high temperatures, and with the increase in H-MSWIFA content, the improvement effect becomes more obvious. The high-temperature stability of the asphalt mixture is not related to H-MSWIFA content but mainly depends on the F/A. Both the F/A and the H-MSWIFA replacement ratio can significantly affect the water stability of the asphalt mixture, specifically, the water stability reaches the best value when the F/A is around 1.0, and the addition of H-MSWIFA harms water stability. Both the F/A and the H-MSWIFA replacement ratio can significantly affect the low-temperature cracking resistance of the asphalt mixture. The higher the F/A, the worse the low-temperature crack resistance. At the same time, the addition of H-MSWIFA harms low-temperature cracking resistance. From the point of view of water stability and low-temperature crack resistance of the asphalt mixture, the H-MSWIFA replacement ratio should not be too high.

The traditional addition method of rejuvenating agent used in the laboratory is inconsistent with the actual situation of the project, which reduces the reliability of the test results. In this paper, the way of premixing rejuvenating agent and Reclaimed Asphalt Pavement (RAP) and extracting asphalt binder is selected, and the modification effect, mechanism, and optimal content of rejuvenating agent on Styrene-Butadiene-Styrene Block Copolymer (SBS) modified asphalt are studied. In this paper, the asphalt in RAP is recycled and restored with different content of regenerant, and the conventional technical performance and Performance Graded (PG) grade of regenerated asphalt was tested. The composite equation of regenerated viscosity of SBS-modified asphalt was analyzed, and the pavement performance of regenerated SBS-modified asphalt mixture with different content of rejuvenating agent and RAP was tested, such as high-temperature stability, low-temperature crack resistance, and water stability. Finally, the determination method of the optimal content of rejuvenating agent was discussed. The results show that it is reliable to predict the viscosity, penetration, and softening point of regenerated asphalt by viscosity logarithmic composite equation. The content of rejuvenating agent has a certain influence on the PG classification of SBS-modified asphalt, which is mainly reflected in the low-temperature critical temperature. There is a certain content of rejuvenating agent to make the high-temperature stability of regenerated SBS-modified asphalt mixture reach the maximum. When the content of rejuvenating agent reaches a certain value, the low-temperature crack resistance and water stability of regenerated SBS-modified asphalt mixture no longer increase significantly with the increase of the content of regenerant. Using the three-level determination method of the optimal content of rejuvenating agent proposed in this paper, the optimal content and reasonable content range of rejuvenating agent can be obtained, which makes the technical performance of regenerated asphalt, PG grade, and the pavement performance of regenerated SBS-modified asphalt mixture meet the specification requirements.

Old cement pavement directly overlaid with an asphalt layer produces many reflection cracks. Using microcrack homogenization technology to treat old cement pavement can effectively reduce the occurrence of reflection cracks. Micro-crack homogenization is relatively mature at the technical level; however, there is relatively little research on its mechanism. To evaluate the microcrack effect of old cement pavement, we conducted core sampling on a project road section after the appearance of microcracks. The core samples were sliced by X-ray tomography (X-ray CT). The mesostructure of the core samples was obtained. The core sample was further divided into microscopic cracks and macroscopic cracks according to the length and width of the crack. The development characteristics of cracks were subdivided into type I-III microcracks and type I-IV cracks. The core-drilling sample was divided into 5652 CT images. The statistical results showed that there were 3582 type-I microcracks, 3197 type-II microcracks, and 1835 type-III microcracks. Among the specimens, the minor proportion of microcracks was 32.87%, the most significant proportion was 100.00%, and the average ratio was 47.51%. Furthermore, the cracks development law and formation mechanism were analyzed based on CT images and cracking statistics. The results showed: (1) The microcrack homogenization process produced many microcracks in the test section and achieved a specific microcrack effect. (2) The cracks produced by the microcrack homogenization process tended to develop along the transition zone of the aggregate–cement mortar interface. The development of microcracks was mainly related to the aggregates’ shape and gradation, as well as the energy required to generate cracks. The research conclusions of this paper can be used as a theoretical basis for the optimization and improvement of the microcrack homogenization process.