Effect of Soaking Time on Compaction and Compressive Strength Performance of Hydrated Lime and Pond Ash Stabilized Modified Peat Soil

Construction designs on peat soil often lead to settlement due to its inability to support loads, necessitating soil stabilization. Pond Ash (PA) and hydrated lime (HL) are commonly used as activation agents to replace cement in soil stabilization. This study aims to investigate the impact of replacing a mixture of hydrated lime (HL) and pond ash (PA) on the mechanical and physical properties enhancement of peat soil. The reaction between lime and pond ash forms calcium silicate, which is responsible for developing the strength of compounds and is highly cost-effective. This study replaces a percentage of peat and the composition of HL and PA, with the aim of contributing to Malaysia’s green sustainability goals across industries by balancing economic expansion and environmental benefits. The percentage of PA content used remains constant at 5, 10, 15, and 20%, while HL is utilized at 3, 6, 9, and 12%. Samples were submerged for varying durations: 0, 3, 7, 14, 21, 28, 60, 90, 120, and 150 days. Results revealed that for untreated peat soil, the moisture content, degree of decomposition, loss of ignition, organic content, specific gravity, and pH ranged from 811-856%, H3-H6, 78.163%, 77.289%, 1.39, and 3.35-3.82, respectively. The optimum moisture content (OMC) and maximum dry density (MDD) were 20.346% and 0.616 mg/m3, respectively, according to the compaction test. The compaction test of peat treated with 9HL10PA yielded the highest MDD (0.71 mg/m3), while soil with 3HL10PA exhibited the lowest MDD (0.62 mg/m3). MDD increased and the OMC decreased with HL content. The resulting unconfined compressive strength (UCS) indicated that samples with lower PA content tended to achieve strength at 60 days and then decrease with further soaking. However, samples with 15 and 20% PA demonstrated more consistent improvement in strength. PA and HL in 2 months and three months show good performance, reaching maximum improvement compared with the native soil. This contributes to the use of the compaction and compressive strength method in geotechnical practices to address settlement issues.