Comparative long-term stabilization of pond ash using lime and cement: FTIR characterization, strength optimization and sustainable utilization

The large-scale generation of pond ash as a byproduct of coal combustion in thermal power plants presents a growing environmental and geotechnical challenge, particularly in countries like India where wet disposal methods occupy vast land areas and pose risks of groundwater contamination. Despite its potential as a sustainable alternative to natural fill materials in construction, the low shear strength and poor gradation of pond ash limit its direct application. While several studies have explored stabilization using binders, limited research provides a comparative, long-term assessment of lime and cement stabilization integrating both microstructural and statistical optimization techniques. This paper proposes a comparative long-term evaluation of the lime and cement stackable stabilizers, which are the two broadly accepted stabilizers of pond ash, and it incorporates the microstructure study and statistical optimization of the study. Different percentages (2−10) of lime and cement were applied on pond ash after which the mixture was allowed to cure within 7 days, 30, and 120 days. Unconfined Compressive Strength (UCS) tests revealed optimal dosages of 6 % cement and 8 % lime, achieving strengths of 2412 kPa and 2719 kPa, respectively, at 120 days. FTIR analysis confirmed the formation of cementitious gels such as C–S–H and C–A–H, correlating with observed strength gains. The use of Response Surface Methodology (RSM) effectively modeled UCS outcomes and identified additive content and curing duration as key predictors of strength. The combined methodology of this study is that of a collective assessment and shows that pond ash stabilization is viable, concerning the cheaper, environmental-friendly material that can be used to carry out geotechnical projects. This result provides useful information that could be incorporated to achieve more efficient designs of mix and encouragement of vast re-use of industrial wastes at infrastructural development.