Green Geotechnics: Sustainable Remediation of Sodium-rich Dispersive Clay Through Potassium and Calcium-rich Waste Transformation

Abstract

A fundamental cause of infrastructure failures, such as road pavements, embankments, slopes, and building foundations, is the dispersion of dispersive clays, which are highly prone to severe erosion. In the construction industry, cement/lime is frequently used to stabilize dispersive clay. However, cement/lime are costly, and their production process produces significant greenhouse gas emissions that cause global warming, underscoring the need for a sustainable, cost-effective, and eco-friendly alternative. Therefore, the study examined the influence of potassium-rich wood ash (KRWA) and calcium-rich fine marble dust (FMD) industrial wastes on dispersion/erosion, index, mechanical, durability, physiochemical, ionic, mineralogical, and microstructure properties. KRWA and FMD amounts varied up to 35% and 50%, respectively, and cured for up to 90 days at about 20 to 25°C. The findings indicate that the KRWA optimal concentration is 10% with 28 days of curing, which reduces dispersion, sodium, plasticity, and compressibility by 82%, 57%, 56%, and 60%, respectively. Moreover, a rapid increase in unconfined compressive strength (UCS) was observed at around 575%, and demonstrated exceptional durability under environmental cyclic conditions, satisfying the accumulated mass loss (AML) criteria of 6% and holding appreciable strength at the end of the 12th wet/dry cycle. In contrast, 20% FMD with 90 days of curing was enough to convert soil into a non-dispersive category and significantly reduced the dispersion, sodium, plasticity, and compressibility by 66%, 62%, 48%, and 64%, respectively. Further, a rapid increase in UCS was observed up to 1648.3%. However, FMD also significantly improved the durability behavior but failed to satisfy the AML criteria. Physicochemical analysis revealed that rapid ion exchange, agglomeration, ABSTRACT

ix and flocculation with minimal curing, followed by long-term pozzolanic reactions, enhanced soil properties. Meanwhile, when rapid results are required with shorter curing times, such as in road construction, embankments, and temporary access roads, where full stabilization over a long period is unnecessary, KRWA is the preferred additive for quick and effective soil stabilization. In contrast, FMD is preferred when quick stabilization is not essential and is ideal for long-term, heavy-duty infrastructure projects, such as building foundations, airports, and highways, where high strength over time is required. Additionally, the cost analysis revealed that the current additive is 6 to 9.6 times more costeffective than conventional additives like cement and lime. Using waste materials in soil stabilization in place of cement/lime lowers environmental pollution and carbon footprint, supporting SDGs #11 and #12. Furthermore, the relationship between dispersivity and various index/mechanical properties has been examined. Results indicated no clear correlation exists between dispersivity and any single soil property. Consequently, multivariable empirical models were developed through rigorous Minitab statistical software testing. Leveraging this understanding, one multivariable empirical model has been designed to identify soil dispersivity from conventional geotechnical tests, achieving a correlation coefficient exceeding 0.87 through traditional tests. Developed empirical models are a practical and precise approach to assessing cohesive soil dispersivity, ensuring safety in engineering projects.