To foster the sustainability of green construction materials utilized in transport infrastructure and generally in soil stabilization for the same purpose, there have been continued efforts towards innovative results for consistent improvement of the mechanical properties of soils. Metakaolin (MK) has been in use as a supplementary material due to its pozzolanic properties. However, it has always produced a limit beyond which there is recorded decline in its ability to cement and strengthen soils in a stabilization protocol. In this research work, a new innovative cementitious material made from 1:1 NaCl + NaOH blend activator mixed with sawdust ash called Ashcrete (A) has been introduced. It is blended with MK in the lateritic soil stabilization procedure. Preliminary results showed that the lateritic soil (LS) has weak consistency with plasticity index above 17%, maximum dry density (MDD) of 1.77 g/cm3 and classified as A-7 soil on American Association State Highway and Transportation Officials (AASHTO) method. The MK and the Ashcrete (A) showed high compositions of aluminosilicates qualifying them as supplementary cements. The MK was used at the rate of 3, 6, and 9%, while the Ashcrete (A) was incorporated at the rate of 2, 4, 6, 8, and 10%. The results of the stabilization exercise showed that the California bearing ratio (CBR) and unconfined compressive strength (UCS) consistently increased with the addition of MK + A blend. This outcome was a shift from the previous work, which had used only MK and recorded 6% addition at which the MK-treated lateritic soil recorded its highest strength, and beyond this mark, there was a decline. The highest strength in this research work was recorded with the stabilization pattern of LS + 9%MK + 10A, which translates to that for a 200 g LS to be treated, 18 g of MK, and 20 g of A are needed to achieve the highest CBR and UCS recorded in this research paper. Finally, the recorded CBR (7-day soaked and unsoaked) and the UCS (7, 21, and 28 days) of the MK + A-treated LS fulfilled the requirements for the construction of a subgrade and subbase.

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.

The application of chemical stabilizers and fibres for the stabilization of weak soil subgrades can mitigate the cost and CO2 emissions associated with pavement construction. The present study evaluates the feasibility of improving clay and sand subgrades using a calcium-based stabilizer (CBS)-commercial name: RBI Grade 81-and synthetic fibre-polyester fibre for building economic and sustainable pavements. Two soils, i.e. silty clay of low plasticity and silty sand, were stabilized and reinforced with independent and combined proportions of the CBS and polyester fibre. The test program included plasticity, compaction, advanced cyclic triaxial (ACT), and California bearing ratio (CBR) tests. The experimental and theoretical resilient moduli were determined using ACT and CBR tests, respectively. Subsequently, scanning electron microscopy and X-ray diffraction tests were then conducted to assess the microstructural and mineralogical changes in the soils due to the stabilization and reinforcement. Flexible pavements were designed with experimental and theoretical resilient modulus (MR). A good correlation was developed between the CBR and experimental MR. The results of the study demonstrate a significant overestimation of MR by the theoretical method. It was seen that with up to 186% higher CBR, 228% higher experimental MR, 96% higher theoretical MR, 230% higher traffic benefit ratio, 22% savings in construction cost, and 24% reduction in greenhouse gas emissions, the stabilized soils exhibited superior performance. The study thus demonstrates that the CBS combined with polyester fibre can be used for economical and sustainable pavement construction.