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.

Soil conditioning technology is usually required to modify the excavated soil to a fluid plastic state during the construction with earth pressure balance (EPB) shield. The steady pressure distribution in the excavation face is linked to soil fluidity. Compared with the slump test, the rheological behavior of the conditioned soil can better reflect the dynamic flow characteristics. A gas-loading rotational rheometer is developed to test the rheological properties of the conditioning agents and the conditioned sandy soil, which can overcome the disadvantage of uneven mechanical loading and create gas-loading conditions. The rheological properties of sandy soil conditioned by different agents under atmospheric and gas-loading pressure conditions were studied, and the influences of foam injection ratio (FIR), bentonite slurry injection ratio (SIR), and polymer injection ratio (PIR) on soil viscosity were analyzed. The test results show that the ambient air pressure only greatly influences the experimental group with foam. Under the same gas-loading pressure, the foam's apparent viscosity decreases with the foam expansion ratio (FER) increasing. The rheological behavior of the conditioned sandy soil conforms to the Bingham model under atmospheric pressure and conforms to the Power Law model when PIR 10 %, the rheological curve of three agents conditioned sand conforms to the Herschel Bulkley model. The higher content polymer reacts with bentonite to increase the soil viscosity, and blocks the foam seepage channel, making it difficult for the foam to re-enter the soil under gas-loading pressure. Investigating the rheological behavior of different conditioned sandy soil provides optimization strategies for EPB performance.