Design optimization and statistical modeling of recycled waste-based additive for a variety of construction scenarios on heaving ground.

To minimize the environmental burdens and to promote natural resource conservation and sustainability, a composite additive (CA) is proposed using paper and wood industry waste, i.e., lignosulphonate (LS) and lime (LM) as a replacement for conventional stabilizers. However, the implication of this proposed stabilizer for real construction scenarios requires a multi-objective optimization for a thorough guideline for practitioners. In this regard, the response surface methodology is used for the mix design optimization of the proposed CA for various construction scenarios (i.e., buildings, roadways, and slopes). An extensive testing program is designed and conducted to obtain different geotechnical parameters related to the mechanical, volumetric change, and hydraulic behavior of the soil with special attention to the stabilization mechanism. The interplay between variables (LS and LM) and responses is examined using the effective 3D surface diagrams, and mathematical models are derived for which the difference between R2, Adj R2, and Pred R2 is found to be less than 0.2. In addition, LM is found to be more sensitive in terms of mechanical and hydraulic parameters than LS whereas LS moderately contributes to altering the parameters related to the volumetric change and hydraulic behavior. The optimized mix design of CA (i.e., LS:LM) is determined against the expansive soil stabilization for foundation, subgrade, and slope stability cases which are found to be 1.03:3.57, 0.84:2.90, and 0.9:2.75 as best suitable for these cases, respectively. Predicted responses for the optimal solution for slope stability cases are found to have an error of 0-9.6%. The stabilization mechanism shows that LS and LM work well in conjunction and lead to a more stable soil structure with better interlocking and cementation between soil particles along with the formation of new cementing materials, i.e., calcium aluminate hydrate (CAH) and calcium silicate gel (CSH). The LS in CA is observed to reduce the LM concentration in soil stabilization by up to 45% with improved geotechnical performance. Thus, the proposed CA is vital for natural resource conservation and paper and wood industry-related waste management.

Remediation methods of heavy metal contaminated soils from environmental and geotechnical standpoints.

Heavy metal contaminated soil (HMCS) threatens world health and sustainable growth, owing to which numerous remediation methods have been devised. Meanwhile, environmental sustainability and geotechnical serviceability of remediated HMCS are important considerations for reusing such soils and achieving sustainable development goals; therefore, these considerations are critically reviewed in this article. For this purpose, different onsite and offsite remediation methods are evaluated from environmental and geotechnical standpoints. It was found that each remediation method has its own merits and limitations in terms of environmental sustainability and geotechnical serviceability; generally, sustainable green remediation (SGR) and cementation are regarded as effective solutions for the problems related to the former and latter, respectively. Overall, the impact of remediation techniques on the environment and geotechnical serviceability is a developing area of study that calls for increased efforts to improve the serviceability, sustainability, reusability and environmental friendliness of the remediated HMCS.