In aggressive environments, including acidic environments, low and high-plasticity clays play an important role in transmitting and spreading dangerous pollution. Stabilisation of these types of soils can improve their characteristics. In this research, different ratios of two precursors with a low calcium percentage, for example, waste statiti-ceramic sphere powder (WS-CSP) and a high calcium percentage (e.g. ground granulated blast furnace slag [GGBFS], were employed to investigate the properties of soils with different plasticity indices [PIs]). Low and high-plasticity-stabilised and stabilised with 5 wt% Portland cement specimens were prepared and exposed to an acidic solution with a pH of 2.5 in intervals of 1, 3, 6 and 9 months. The long-term durability of specimens was evaluated using the uniaxial compressive strength test (UCS) and bending strength test (BS). Additionally, the microstructures of these specimens under various time intervals were analyzed using scanning electron microscopy and Fourier-transform infrared. According to the results, in an acidic environment, the reduction in UCS, BS, toughness and secant modulus of elasticity (E50) for low-plasticity-stabilised specimens and containing 100% WS-CSP was lower than that of other specimens. The Taguchi method and ANOVA were used to investigate the effect of each control factor on the UCS and BS.

Calcium carbide residue (CCR), a calcium-rich industrial waste, shows promise in improving mechanical properties of weak soils when used alone or in combination with pozzolanic materials and alkaline activators. This study comprehensively investigated the mechanical performance and stabilisation mechanism of CCR, CCR-fly ash, and alkaline-activated CCR-fly ash on kaolin clay, aiming to clarify their differences in mechanisms, identify their limitations, and promote effective application. The contribution of CCR, fly ash, alkaline activator, and initial water content of soil on enhancing soil strength was quantitively assessed through signal-to-noise ratio and analysis of variance (ANOVA) based on the Taguchi method. The stabilisation mechanism of different CCR-based materials was investigated by assessing the morphological and mineralogical features of stabilised samples. Taguchi analysis revealed that the development of soil strength was primarily influenced by initial water content in the early curing stage, while the contribution of fly ash became larger over time. Variation in CCR content had a limited effect on soil strength across all curing periods, as indicated by low contribution values and low statistical significance in ANOVA. The microstructural analyses revealed a low degree of formation of C-S-H and CA-H gels in soil stabilised with CCR alone and CCR combined with fly ash, while alkaline activated CCR-fly ash stabilised soil exhibited the coexistence of C-A-S-H and N-A-S-H gels. Taguchi superposition model was effectively used to estimate compressive strength results and supported the determination of suitable CCR-based materials for specific strength requirements.

Expansive soils are known as geotechnically problematic soils and represent a significant challenge for both civil engineering and geotechnical applications. The primary issue with expansive soils is their susceptibility to moisture-induced volume changes, resulting in both shrinkage and swelling behaviors. This study presents a comprehensive investigation into optimizing the physical and strength properties of expansive soil through the use of cellulose-based fiber additives, namely bamboo fiber (BF), rice husk fiber (RHF), and wheat straw fiber (WSF). Various fiber dosages (5 %, 10 %, and 15 %) and sizes (75 mu m, 150 mu m, and 300 mu m) were employed in combinations to identify the optimal conditions and analyze the soil-fiber reinforcement mechanisms. The experimental design was leveraged by the Taguchi method to optimize conditions, focusing on key response factors such as the Atterberg limit test (PI, LL), free swell ratio (FSR), linear shrinkage (LS), and unconfined compressive strength (UCS) and statistical analysis for results were validated by Analysis of Variance (ANOVA). Additionally, cellulose content and water absorption capacity were assessed to confirm the suitability of cellulose-based fibers as soil stabilizers. Hence, the results demonstrate a substantial enhancement in both the physical and mechanical properties of the stabilized soil with the incorporation of cellulose-based fiber additives. Specifically, the Plastic Index (PI) improved by 85 % when using RHF fibers at a dosage and size of 15 % and 300 mu m, respectively. The Free Swell Ratio (FSR) witnessed improvement with WSF fibers at a dosage of 15 % and a size of 150 mu m. Linear shrinkage exhibited remarkable improvement, exceeding 95 %, with a combination of 15 % and 75 mu m fibers. Furthermore, the Unconfined Compressive Strength (UCS) values were improved by more than 100 % when using 15 % BF fibers with a size of 300 mu m. Therefore, the findings of the study highlight that cellulosebased additives as highly effective and sustainable alternatives for soil stabilization, surpassing the engineering performance of traditional soil stabilizers