Assessment of the environmental impacts of utilizing coal ashes and OPC for soil stabilization applications: Leachate analysis in response to rainfall interaction

The construction industry is a leading sector for coal ashes utilization, including in cement manufacturing and soil stabilization applications. In soil stabilization, coal ashes, alongside Ordinary Portland Cement (OPC), are the most commonly used materials. However, the environmental impact of coal ashes, particularly the leaching of heavy metals from stabilized soil when exposed to rainfall, remains underexplored. There is a notable gap in assessing the environmental impacts of this utilization, particularly when the stabilized soil interacts with rainfall in real-world scenarios. Therefore, this study aimed to contribute to filling this gap. Accordingly, in this study, peat soil was stabilized by using fly ash, bottom ash, and OPC. The characterization of soil mixture materials, including physicochemical and engineering properties, was established and studied first. Following the environmental impact, simulations were conducted using a column to study soil leachate under different conditions and seasons (dry and wet) in response to its interaction with rainfall. The leachate was analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to measure the concentrations of heavy metals, including copper (Cu), aluminum (Al), manganese (Mn), iron (Fe), and zinc (Zn). Additionally, Ion Chromatography (IC) was employed to determine the concentrations of major anions, including fluoride (F⁻), chloride (Cl⁻), nitrate (NO₃⁻), phosphate (PO₄³⁻), and sulfate (SO₄²⁻). The findings revealed the complex interaction of the chemical stabilization processes and environmental factors with the leaching behavior of heavy metals and anions, highlighting the significant impact of stabilization on leaching patterns. To conclude, this study provides a valuable contribution to understanding the environmental and engineering implications of utilizing coal ashes in soil stabilization.