The construction industry is increasingly focusing on sustainability, creating a need for innovative materials. This comprehensive review examines the potential of calcined clays and nanoclays in enhancing construction materials and promoting resilient infrastructure. It emphasises their role in improving performance and supporting environmental conservation in sustainable development. The review discusses how varying proportions of calcined clays and nanoclays impact the performance of pavement materials, especially when combined with bitumen in asphalt mixtures. It highlights their benefits, including reduced chloride penetration, enhanced water resistance, and improved soil conductivity. Overall, the review suggests that the strategic integration of calcined clays and nanoclays into construction materials can enhance durability, optimise resource use, and support environmental sustainability.

The mechanical characteristics of asphalt mixture are closely related with its stress state, temperature, and loading rate, therefore, the loading condition of the asphalt mixture's dynamic modulus test should be consistent with the actual temperature, loading frequency, and stress state that are applied to the mixture in actual pavement, thus can the test produce an objective result that can accurately reflect the actual stress-strain relationship for the asphalt mixture. However, due to limitations in the loading capacity of current dynamic modulus test equipment, the present modulus tester cannot yet set such a loading condition whose stress state is consistent with that of asphalt mixture in actual pavement. As a result, the modulus testing results of the current test may not accurately reflect the actual stress-strain characteristics of an asphalt mixture under real traffic loads. Therefore, this paper aims to figure out the impact of stress state on asphalt mixture's dynamic modulus, and firstly conducts a numerical analysis to ascertain asphalt pavement's triaxial stress state at different depth, then, utilizing the nonlinear elasticity theory of Soil Plasticity, proposes a theoretical model that can reflect triaxial stress state's effect on asphalt mixture's dynamic modulus, and then, arranges a series of triaxial dynamic modulus tests for asphalt mixture in different stress state to verify the model's effectiveness, and meantime analyzes stress state's influencing rule to asphalt mixture's dynamic modulus. Their results indicate, the asphalt mixture of the actual pavement is in an obvious triaxial stress state, and that the higher the triaxial stress state, the larger the dynamic modulus, particularly for the mixture near the surface, whose high stress state will lead to their dynamic modulus to be significantly larger than that of the underlying course, while the model proposed in this paper can to a large extent reflect this impact.

This study was conducted to investigate the hydrostatic stability of a steel slag porous asphalt mixture (SSPA) under freeze-thaw cycles in seasonal frozen soil areas and thereafter, compare its (SSPA) characteristic properties and advantages with a traditional porous asphalt pavement. In the study, the freeze-thaw stability of SSPA was tested through multiple freeze-thaw cycle splitting, scattering loss, and trabecular bending tests under various cyclic temperature water immersion conditions including quantitatively analyzing the SSPA volumetric changes. In addition, the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) tests were used to analyze the microscopic damage mechanism of SSPA after being subjected to various cyclic temperature water immersion conditions. The corresponding test results indicated that: (a) the long-term freeze-thaw cycles had significant adverse effects on the hydrostatic stability, physical/mechanical properties, and volume stability of SSPA; and (b) when the melting temperature was increased, both the hydrostatic stability and mass gain/loss ratio of SSPA decreased whilst the void ratio increased. On the other hand, the SEM and EDS results showed that an increase in the number of freeze-thaw cycles or melting temperature led to a corresponding increase in the width of the steel slag-asphalt transition zone. This resulted in a weakening of the mechanical connection and anchorage between steel slag and asphalt, as well as the destruction of their adhesion bond. However, the short-term freeze-thaw cycles had little effect on the hydrostatic stability of SSPA because the steel slag-asphalt interfacial strength was enhanced by shortterm freeze-thaw cycles.

Large amounts of steel slag (SS) stockpiled and buried leads to land occupation, and is prone to cause soil and water contamination. Partially replacing natural minerals in pavement construction can contribute to the rapid consumption of stockpiled SS, but its poor volume stability limits its widespread adoption into engineering applications. Meanwhile, the potential leaching of hazardous substances (HS) should also be emphasized. This study prepared different pretreated SSs and asphalt mixtures. The differences and improvement mechanisms of the pretreatment on the SS properties were investigated through micro-morphology and chemical composition analyses. The physical properties of different SS and the long-term volume stability and moisture damage resistance of the steel slag asphalt mixture (SSAM) were tested. Moreover, a revised HS leaching test method for the SSAM was proposed, and the effectiveness of various pretreatment methods in reducing HS leaching was evaluated. The results revealed that the porous characteristics and free oxides contained in SS were the main obstacles to their large-scale application in pavement engineering. Natural aging, thermal immersion, and acid modification alter the composition of SS through chemical reactions and accelerate the consumption of free oxides. The polymer film formed by the silane coupling agent on the SS surface mitigated the environmental effects on the performance. The long-term performance of the SSAMs was improved, and the amount of HS precipitated was significantly reduced. Acetic acid modification and surface treatments are recommended because they are more effective in improving moisture damage resistance and reducing potential adverse environmental impacts. The findings are significant for reasonable pretreatment and application of converted SS as well as for contributing to the sustainable development of transportation infrastructure.

The surging quest for asphalt pavement sustainable approaches promotes the need for balancing environmental and economic benefits. With the global production of waste plastics (WP) reaching drastic levels and recycling rates remaining disappointingly low, policymakers are increasingly advocating for the reuse of post -consumer recycled plastics in construction materials. In this study, recycling WP emerges as the most feasible solution, particularly when considering the environmental hazards associated with burning and landfilling, such as air and soil pollution. Recycling WP in asphalt mixture specifically has been quested due to the high -daily production of asphalt mixture, but concerns exist regarding its engineering performance. This study's focus is to assess the asphalt mixture mechanical response while incorporating WP, particularly High -Density Polyethylene (HP), in addition to assessing their environmental impacts. Four asphalt mixtures were rigorously evaluated containing four different asphalt binders: polymer -modified PG 76-22 and PG 70-22, unmodified PG 67-22, and HPmodified PG 67-22 asphalt binders. The investigation encompassed an in-depth analysis of asphalt binder rheological characteristics and asphalt mixtures' mechanical properties. A pivotal aspect of this study was comparing the environmental benefits of HP -modified asphalt binders against conventional polymer -modified ones. This comparison was conducted through a detailed cradle -to -gate life -cycle assessment (LCA). Results indicate that asphalt mixture containing WP material demonstrated similar engineering performance as compared to conventional mixture containing PG 70-22 asphalt binder. Further, the LCA analysis revealed that the inclusion of HP WP in asphalt binders, as compared to PG 76-22 and PG 70-22 asphalt binders, can significantly lower the global warming potential by 17.7% and 8.9%, respectively.

Asphalt mixture is a typical granular material, and its macroscopic properties are closely related to the interaction behavior of aggregate particles at the micro scales. Discrete element method (DEM), as an important numerical simulation method in granular mechanics, plays an increasingly important role in analyzing the aggregate packing characteristics, skeleton features, predicting mechanical and pavement performance of asphalt mixtures. However, the complexity of the composition of asphalt mixtures, including the particle size, shape, spatial distribution of aggregate particles, and the viscoelasticity of asphalt binders sensitive to temperature, load, and time, increases the difficulty of constructing DEM models of asphalt mixtures, selecting contact constitutive models, and determining parameters, which directly affects the accuracy and efficiency of DEM simulations. In this review, the generation methods of idealized models, image models, and user-defined models currently used to generate DEM models of asphalt mixtures were summarized in detail. Conventional contact constitutive models, including elastic and viscoelastic contact stiffness constitutive models, as well as fracture models including bonding models and cohesive softening models, were discussed. Moreover, special contact constitutive models, such as damage, self-healing, and two-stage contact models considering compaction evolution, were also summarized and discussed. Then, the contact constitutive model parameters were classified and related determination methods were summarized, and the latest application directions of DEM in current asphalt mixture research were classified. On this basis, relevant discussions were carried out, and the challenges and future development prospects faced by DEM in asphalt mixture research were proposed.