This study developed a design framework for porous mixtures using a 100% sustainable non-bituminous epoxy–polyurethane binder system. Conventional design protocols for porous asphalt mixtures exhibit limitations in accurately controlling void content and mixture composition. This study proposed a novel design framework for porous mixtures containing 100% sustainable binder based on statistical analysis and theoretical calculations. The relationships among target air voids, binder content, and aggregate gradation were systematically analyzed, and calculation formulas for coarse aggregate, fine aggregate, and mineral filler contents were derived. A mix design framework was further established by applying the void-filling theory, where the combined volume of binder, fine aggregate, and filler equals the void volume of the coarse aggregate skeleton, thereby ensuring precise control of the target void ratio. Additionally, mixing procedures were investigated with emphasis on feeding sequence, compaction method, and mixing temperature. Results indicated that the optimized feeding sequence significantly improved binder distribution; specimens compacted using the Marshall double-sided compaction method achieved a density of 89.60%. Rheological analysis revealed that at 30 °C, the viscosities of sustainable binder and polyurethane filler were 1280 mPa·s and 6825 mPa·s, respectively, suggesting optimal mixture uniformity. The proposed methodology and process parameters provide essential technical guidance for engineering applications of porous mixtures containing 100% sustainable binder.

Metakaolin-based geopolymer is considered a potential alternative to traditional cement materials; however, its fresh paste typically suffers from high viscosity and poor workability. To evaluate the effect of superplasticizers, this study first optimized the basic mix proportions of alkali-activated metakaolin geopolymer through orthogonal testing. The influences of five superplasticizers—melamine, sodium lignosulfonate, naphthalene-based, polycarboxylate, and KH-550 at varying dosages were then examined in terms of flowability and compressive strength. The mechanisms of superplasticizer action were further investigated by means of physical stability assessment, Fourier-transform infrared spectroscopy (FTIR), surface tension, and zeta potential testing. The results indicate that the optimal mix design for the metakaolin-based geopolymer is achieved with a silicate modulus of 0.9, a liquid-to-solid ratio of 0.75, and a silica fume content of 15%, leading to a 28-day compressive strength of 58.8 MPa and a flow diameter of 132 mm. Compared with other superplasticizer, sodium lignosulfonate exhibited superior water-reducing efficiency and stability, while its adverse effect on compressive strength was acceptable. Balancing workability and strength requirements, the optimal dosage was determined to be 1.5%. Mechanism analysis further revealed that superplasticizer can enhance electrostatic repulsion between particles, thereby improving the flowability of metakaolin-based geopolymers. This research provides a viable pathway for preparing metakaolin-based geopolymers with superior mechanical properties and workability.

Crumb rubber was incorporated into neat bitumen at a dosage of 15 wt% to mitigate the challenges of rising crude oil prices, high dependence on fossil fuels, and energy shortages. Both the unmodified bitumen and crumb rubber modified bitumen (CRMB) were subjected to short- and severe long-term ageing. The rheological properties were evaluated using a dynamic shear rheometer (DSR) and a bending beam rheometer (BBR) to investigate the high-, intermediate-, and low-temperature performance of the binders under different ageing conditions. Fourier-transform infrared spectroscopy (FTIR) was employed to characterise the chemical changes with modification and ageing. The results indicate that the incorporation of crumb rubber significantly enhances the high- and low-temperature performance of bitumen but slightly reduces its fatigue resistance and durability. Crumb rubber does not alter the oxidation pathway of bitumen. After severe long-term ageing, the chemical characteristics of CRMB remain comparable to those of neat bitumen.

Recently, researchers in the road field are focusing on the development of green asphalt materials with lower emission of volatile organic compounds (VOCs). The characterization methodology of asphalt VOCs and the influencing factors on VOCs release have always been the basic issue of asphalt VOCs emission reduction research. Researchers have proposed a variety of asphalt VOCs characterization methodologies, which also have mutually irreplaceable characteristics. Asphalt VOCs volatilization is affected by many factors. In this study, asphalt VOCs characterization methodologies were summarized, including their advantages, disadvantages, characteristics and applicable requirements. Subsequently, the influencing factors of VOCs release, such as asphalt types and environment conditions, are summarized to provide theoretical support for the emission reduction research. The classification and mechanism of newly-development asphalt VOCs emission reduction materials are reviewed. The reduction efficiencies are also compared to select better materials and put forward the improvement objective of new materials and new processes. In addition, the prospects about development of VOCs release mechanism of asphalt materials during the full life cycle and feasibility research of high-efficiency composite emission reduction materials in the future were put forward.

Polycyclic Aromatic Hydrocarbons (PAHs) in asphalt materials is a type of serious environmental hazard, and the main pollution resource in road engineering. Aiming at the requirement of PAHs rapid detection method in asphalt pavement construction for low environmental hazard, this research concentrated in experiments about PAHs content, fluorescence characteristics, solvent environment impact mechanism and correlation between fluorescence intensity and concentration in different asphalt materials, based on the fluorescence effect of PAHs from condensed ring structure. It is found that coal tar asphalt has a typical aggregation-caused quenching phenomenon and higher fluorescence quantum efficiency. Taking the three solvent environment parameters polarity, viscosity and pH value as the research objects, the optimal solvent environment for the fluorescence phenomenon of PAHs in asphalt materials was explored and established as dimethyl sulfoxide: tetrahydrofuran: deionized water: glycerol = 1 : 1 : 1 : 2. Under the optimal solvent environment, fluorescence intensity and concentration of the three asphalt materials all showed obvious linear relationship. Under the same concentration condition, fluorescence intensity of asphalt material showed positive correlation with the PAHs content. This study proves that the asphalt material has the linear relationship between fluorescence intensity and PAHs concentration, which will provide theoretical basis for the detection of PAHs content in asphalt materials, and support the development of low environmental hazard in construction technology for road engineering.

The reuse in high-value materials is one of the important resource utilization approaches of phosphorus tailings. At present, a mature technical system has been formed on the reuse of phosphorus slag in building materials, and silicon fertilizers in the extraction of yellow phosphorus. But there is a lack of research on the high-value reuse of phosphorus tailings. In order to make safe and effective utilization of phosphorus tailing resources, this research concentrated on how to solve easy agglomeration and difficult dispersion of phosphorus tailing micro-powder, when it was recycled in road asphalt. In the experimental procedure, phosphorus tailing micro-powder is treated in two methods. One method is to directly add it with different contents in asphalt to form a mortar. Dynamic shear tests were used to explore the effect of phosphorus tailing micro-powder on the high-temperature rheological properties of asphalt influence mechanism of material service behavior. The other method is to replace the mineral powder in asphalt mixture. The effect of phosphate tailing micro-powder on the water damage resistance in open-graded friction course (OGFC) asphalt mixtures was illustrated, based on the Marshall stability test and the freeze–thaw split test. The research results show that the performance indicators of the modified phosphorus tailing micro-powder meet the requirements for mineral powder in road engineering. Compared with standard OGFC asphalt mixtures, the residual stability of immersion and freeze–thaw splitting strength were improved when replace the mineral powder. The residual stability of immersion increased from 84.70% to 88.31%, and freeze–thaw splitting strength increased from 79.07% to 82.61%. The results indicate that phosphate tailing micro-powder has a certain positive effect on the water damage resistance. These performance improvements can be attributed to the larger specific surface area for phosphate tailing micro-powder than ordinary mineral powder, which can effectively adsorb asphalt and form structural asphalt. The research results are expected to support the large-scale reuse of phosphorus tailing powder in road engineering.