Anita Setyowati Srie Gunarti, Yulvi Zaika, As’Ad Munawir, Eko Andi Suryo, Harimurti
The rainy season often causes water pooling on the ground surface, a rise in groundwater levels, and swelling in expansive soils. Swelling in expansive soils has poor mechanical properties, resulting in low subgrade bearing capacity, which makes road construction prone to damage. Improving expansive soil subgrades using waste materials with specific properties that can effectively reduce swelling potential has proven to be effective. This study aims to identify the optimal thickness of stabilized expansive soil subgrade using fly ash (FA) and waste foundry sand (WFS) that can reduce swelling potential and improve bearing pressure characteristics under wet conditions. The concentration of FA used was 15%, whereas the concentration of WFS was 20%; both were based on the soil’s dry weight and modeled as a 30 cm-high subgrade with varying stabilized soil thicknesses. In this study, a swelling test was conducted by introducing water into the subgrade, followed by a plate load test to determine the bearing pressure and settlement. Loading tests were conducted on 5 subgrade variants that had undergone curing for 4 days and wetting for 4 days. The results of the wetting and swelling tests on the stabilized soil subgrade with a thickness of 30 cm (V4) showed a smaller swelling percentage compared to subgrade V0, reducing swelling from 7% to 3.7% due to changes in moisture content, and reduced the swelling pressure from 50.17 kPa to 25.34 kPa. Subgrade V4 reduced the swelling potential and swelling pressure by almost 2 times that of the untreated soil subgrade variant (V0). The subgrade with the best performance under wet conditions is subgrade V4, with a 100% improvement, which is a 30 cm thick stabilized soil layer, showing a pressure increase of 214.91% compared to the untreated soil subgrade (V0) at a 7 mm settlement with a BPR of 3.15. © The Author(s) 2025.
Department of Civil Engineering, Universitas Pertahanan Republik Indonesia (Unhan RI), Bogor Regency, West Java, 16810, Indonesia; Department of Civil Engineering, Universitas Brawijaya, 167 M. T. Haryono str, Malang, 65145, Indonesia
