Polyacrylamide improves the strength of peat soil while reducing cement consumption: An experimental and machine learning investigation

Peat soil presents poor geotechnical properties, posing significant risks to structural stability when used as a foundation material. This study investigates the potential of polyacrylamide (PAM) as an adhesive additive to enhance the strength of peat soil stabilized with cement and sand. Unconfined compressive strength (UCS) tests were conducted to evaluate PAM's effectiveness, complemented by microscopic analyses to explore underlying improvement mechanisms. Results show that PAM significantly increases soil strength, with higher PAM content yielding greater gains. Specifically, adding 10 % PAM boosts the UCS of untreated peat soil by up to 2.5 times and improves the strength of peat soil treated with 30 % cement and 30 % sand by 174.1 kPa. PAM also reduces soil permeability without exhibiting ecotoxicity. Microscopic observations reveal that PAM forms cross-linked gel networks that bind soil particles into large aggregates. 10 % PAM decreases the specific surface area, pore volume, and average pore size by 32.6 %, 42.2 %, and 21.4 %, respectively. Importantly, PAM does not alter the chemical composition of the stabilized soil and remains stable over time. Finally, a gene expression programming (GEP) algorithm was used to develop a predictive mathematical model for UCS, achieving a coefficient of determination (R²) above 0.97. An analysis of cement consumption using this model indicates that incorporating 10 % PAM can reduce cement consumption by 26.1 % to achieve a target strength of 300 kPa, compared with using only cement and sand. These findings demonstrate that PAM is an effective and environmentally beneficial stabilizer for peat soil.