Soybean-derived bio-oil is one of the vegetable-based oils that is gaining the most interest for potential use in the rejuvenation of aged asphalt binders. This laboratory study was conducted to characterize and quantify the diffusion and rheological properties of bio-oil-rejuvenated aged asphalt binder (BRAA) using soybean oil. In the study, the chemical structure of the soybean oil was comparatively characterized using an element analyzer (EA), gel permeation chromatography (GPC), and a Fourier infrared (FTIR) spectrometer, respectively. Based on the chemical structure of the bio-oil, BRAA molecular models were built for computing the diffusion parameters using molecular dynamic simulations. Likewise, a dynamic shear rheometer (DSR) test device was used for measuring and quantifying the rheological properties of the aged asphalt binder rejuvenated with 0%, 1%, 2%, 3%, 4%, and 5% soybean oil, respectively. The laboratory test results indicate that bio-oil could potentially improve the diffusion coefficients and phase angle of the aged asphalt binder. Similarly, the corresponding decrease in the complex shear modulus has a positive effect on the low-temperature properties of BRAA. For a bio-oil dosage 4.0%, the diffusion coefficients of the BRAA components are 1.52 × 10⁻⁸, 1.33 × 10⁻⁸, 3.47 × 10⁻⁸, 4.82 × 10⁻⁸ and 3.92 × 10⁻⁸, respectively. Similarly, the corresponding reduction in the complex shear modulus from 1.27 × 10⁷ Pa to 4.0 × 10⁵ Pa suggests an improvement in the low-temperature properties of BRAA. Overall, the study contributes to the literature on the potential use of soybean-derived bio-oil as a rejuvenator of aged asphalt binders.

Waste plastic, such as polyethylene (PE), and waste rubber tires, are pollutants that adversely affect the environment. Thus, the ways these materials are used are important in realizing the goals of reduced CO₂ emissions and carbon neutrality. This paper investigates the fundamental properties, compatibility, and interaction mechanism of waste plastic/rubber-modified asphalt (WPRMA). Dynamic shear rheology, fluorescence microscopy, a differential scanning calorimeter, and molecular dynamic simulation software were used to evaluate the properties and mechanisms of WPRMA. The results show that the anti-rutting temperature of WPRMA with different waste plastic contents is higher than 60 °C and the optimal dosage of waste PE in WPRMA is 8%, which can enhance the high-temperature properties and compatibility of rubber-modified asphalt. The temperature can directly promote the melting and decomposition of the functional groups in WPRMA and thus must be strictly controlled during the mix production process. The interaction mechanism suggests that waste plastic can form networks and package the rubber particles in rubber-modified asphalt. The main force between waste plastic and rubber is Van der Waals force, which rarely occurs in chemical reactions.

With the increasing traffic loading and changing climatic conditions, there is a need to use novel superior performing pavement materials such as high-modulus asphalt binders and asphalt mixtures to mitigate field distress such as rutting, cracking, etc. This laboratory study was thus conducted to explore and substantiate the usage of Rubber Polymer Composite Modifier (RPCM) for high-modulus asphalt binder modification. The base asphalt binder used in the study comprised A-70# Petroleum asphalt binder with RPCM dosages of 0.25%, 0.30%, 0.35%, 0.40% and 0.45%, separately. The laboratory tests conducted for characterizing the asphalt binder rheological and morphological properties included the dynamic mechanical analysis (DM), temperature-frequency sweep in the dynamic shear rheometer (DSR) device, bending beam rheometer (BBR), and florescence microscopic (FM) imaging. The corresponding test results exhibited satisfactory compatibility and potential for using RPCM as a high-modulus asphalt binder modifier to enhance the base asphalt binder’s rheological properties, both with respect to high- and low-temperature performance improvements. For the A-70# Petroleum asphalt binder that was evaluated, the optimum RPCM dosage was found to be 0.30–0.35%. In comparison to styrene–butadiene–styrene (SBS), asphalt binder modification with RPCM exhibited superior high-temperature rutting resistance properties (as measured in terms of the complex modulus and phase angle) and vice versa for the low-temperature cracking properties. Overall, the study beneficially contributes to the literature through provision of a reference datum toward the exploratory usage of RPCM for high-modulus asphalt binder modification and performance enhancements.

At present, the task of maintaining and managing rural roads in China is becoming increasingly severe. To solve the problems of insufficient scheme benefits, complex feasible solutions, and low optimization efficiency in long-term maintenance planning of rural road networks under a limited budget, it is urgent to develop maintenance decision-making models and optimization methods suitable for rural roads in China. This paper focuses on the critical aspects of performance evaluation, prediction, and decision-making. Firstly, this paper proposes evaluation indicators and maintenance countermeasures suitable for rural roads, combining them with the characteristics of rural road performance degradation. Based on different treatment measure levels, RPCI and RRQI performance prediction models are established. On this basis, an improved heuristic optimization method is proposed, which realizes rapid optimization of the most cost-effective solution. Finally, the model and method proposed in this paper are applied to the case analysis of 10 rural roads in Haimen City, generating 171 optimal maintenance sections, further verifying the feasibility and effectiveness of the model. The study provides a theoretical basis for the scientific management of rural road maintenance.

Different characteristics of aggregates has significant impact on the high modulus mixture properties of hard asphalt (such as high temperature properties, modulus, and fatigue resistance). This paper chooses two kinds of aggregates (basalt and limestone) with obvious differences. Based on the Aggregate Image Measurement System (AIMS), this paper made detailed comparison and analysis on all characteristics of the two kinds of aggregates. Referring to the French high modulus mix design process, the various performance indicators coordinated design methods were tested on the high modulus mixture of hard asphalt. Results show that, it can be achieved a balanced design of high temperature performance, modulus, and fatigue resistance properties on the mixture thronging the gradation and the hard asphalt dosage adjustment, for different properties aggregate.