Hassan Mujtaba

Dispersive soils are well‐known for producing instability issues in earth structures because they easily disperse when exposed to water. Rainfall infiltration can gradually dislocate fine particles from the pavement subgrades. Which weakens the structure over time. In this study, a stabilization technique based on a waste‐derived calcium composite of CLS and hydrated calcium sulphate (HCS) is investigated. A 5 × 5 m multiple test sections were re‐laid, treated with the CLS–HCS mixture on an existing embankment. The effectiveness of the treatment was evaluated using both field measurements and laboratory tests. Pinhole tests and validating chemical indicators demonstrated that the stabilization considerably transformed the soil's behavior from dispersive into non‐dispersive. The mechanical properties were significantly improved. In comparison to the untreated dispersive soil, the California bearing ratio resulted in an improvement of 287% and the unconfined compressive strength enhanced by 138%. Static repetitive plate load testing in the field presented that the permanent deformation during cyclic loading dropped by 65.3% and the strain modulus improved by 57.5%, from 40.2 MPa to 63.3 MPa. These modifications show an obvious rise in subgrade stiffness and resistance to repeated loads. A multivariable regression model was then created to estimate field strain modulus by utilizing measurable soil parameters such as dry density, moisture content, plasticity index, fines content, and exchangeable sodium percentage. The measured field values and the model agreed well ( R ² = 0.97). According to AASHTO 1993 empirical pavement design study, increased subgrade stiffness enables a 25%–30% reduction in granular base thickness, which results in material savings for pavement construction. When compared to traditional quicklime stabilization, life cycle evaluation also depicted significant life cycle benefits. Overall, the findings illustrate that, in field settings, the CLS–HCS composite can offer a workable and sustainable solution for enhancing dispersive soil subgrades properties.

The present study evaluates the amelioration of fat clay by blending it with cohesive non-swelling soil (CNS) and cohesionless silty sandy soil (Kassu). The fat clay sample with a liquid limit (LL) of 50 and a plasticity index (PI) of 26 was collected from Narowal, while CNS and Kassu samples were procured from Lahore's outskirts. Geotechnical tests on the virgin soil indicated its unsuitability for construction. Laboratory tests, including modified Proctor compaction, unconfined compression, California bearing ratio (CBR), and one-dimensional consolidation, were performed on samples blended with 0–35% CNS or Kassu in 5% intervals. The LL and PI of fat clay decreased significantly with the addition of 35% CNS (LL: 50–32%, PI: 24 to 13) and Kassu (LL: 50–29%, PI: 24–12). The CBR value increased from 4 to 7%, making the blended soil suitable for subgrade use. Unconfined compression tests showed a strength increase from 102 to 185 kPa with 35% CNS and up to 140 kPa with 25% Kassu. Compaction tests revealed improved maximum dry unit weight and reduced optimum moisture content. Swell potential decreased from 4 to 1.2 and 0.26% with CNS and Kassu additions. Regression models predict swell pressure and ultimate swell potential. The study concludes that blending fat clay with CNS and Kassu significantly improves its geotechnical properties, with CNS being more effective in controlling swell characteristics.

Natural disasters and human demolition create vast amounts of construction and demolition waste (CDW), with a substantial portion being concrete waste. Managing this concrete waste is a daunting challenge for developing countries with limited resources, aiming to mitigate its harmful environmental effects. Therefore, the proposed approach involves using recycled fine aggregates (RFA) instead of fresh fine aggregates (FFA) in concrete, which aligns closely with achieving sustainable environmental objectives. Extensive laboratory tests were conducted to assess the effects of adding RFA to concrete. The influence of 0 to 100% RFA replacement and different curing times was investigated on compressive strength, tensile strength, resistance against chloride ion penetration and chemicals exposure, and quality of aggregates. So, around 30%, 35%, 20%, and 79% reductions in compression strength, tensile strength, modulus of elasticity, and workability were estimated when 100% RFA was used in recycled aggregate concrete (RAC). However, according to results analyses, the performance of RAC is reliable up to 50% of RFA in proposed conditions and mix design. In addition, major environmental impacts such as global warming potential, aquatic eutrophication, and aquatic acidification were reduced by 47%, 40%, and 18%, respectively, for concrete having 50% RFA than concrete having 100% FFA.

Agro-synthetic stabilization of high-plastic clay is trending due to its vital role in sustainable geotechnical construction and maintenance of clay subgrade. Remoulded samples of high plastic clay (C), ameliorated by optimal doses of 1.2% polyester (P) and 0.9% banana (B) at maximum dry density (γ_dmax) and optimum moisture content (OMC), were subjected to swell potential, unconsolidated undrained (CU) triaxial, consolidation, and California bearing ratio (CBR) tests. The outcome of this research presents that the use of an optimal clay-polyester-banana (CPB) mix enhanced the secant elastic modulus (E₅₀), peak strength (S_p), and CBR by 2.5, 2.43, and 2.7 times, respectively; increased E₅₀/C_c increased from 12.29 to 53.75 MPa; and lowered the swell potential by 48% and compression index (C_c) by 42.8%. It was also observed that the increase in moisture content (m_c) of the optimal CPB mix from 20% (unsaturated phase) to 32% (wet phase) decreased S_p from 212 kPa to 56 kPa and E₅₀ from 8.42 MPa to 2.16 MPa, whereas C_c was increased from 0.16 to 0.26, depicting the potential use of the CPB mix as a stable and sustainable geotechnical material even in wet seasons. Novel correlations are developed for the prediction of C_c from m_c, E₅₀, and S_p for an optimal CPB mix to achieve sustainable geotechnical systems and designs in sustainable geo-environmental engineering.