Document Type : Original Article

Authors

• Reza Tadayonfar ¹
• Mostafa Mohammadian ²
• Morteza Salari ³

¹ Assistant Professor Civil Engineering Dept., Faculty of Engineering, Hakim Sabzevari University, Sabzevar, Iran

² Civil Engineering Dept., Faculty of Engineering, Rouzbahan Institute of Higher Education Non-profit - NGOs, Sari, Iran.

³ Civil Engineering Dept., Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran.

Abstract

Low-plasticity fine-grained soil (ML) exhibit poor geotechnical stability due to weak interparticle bonding and moisture sensitivity, while traditional stabilizers like cement and lime face environmental restrictions in urban areas. This laboratory study evaluates a low-carbon stabilization approach using a butyl acrylate–methyl methacrylate (BA–MMA) copolymer emulsion (2%–9% by dry weight) on a fine-grained soil from Sabzevar, Iran. Specimens cured for 3 hours, 1 day, and 7 days were subjected to Atterberg limits, standard Proctor compaction, and unconfined compressive strength (UCS) tests. Notably, the contribution of matric suction was decoupled from the net polymeric strengthening effect. Results showed that the BA–MMA copolymer modified water-particle interactions and encapsulated soil grains, reducing the plasticity index by 31% (from 8.4 to 5.8) while leaving the plastic limit virtually unchanged. Polymer modification enhanced compaction, increasing maximum dry density by 6% (from 1.69 to 1.79 g/cm³) and reducing optimum moisture content by 12%; the optimum compaction efficiency occurred between 5% and 7% polymer content. Corrected UCS results revealed that the net polymer-induced strength was negligible initially, but reached 0.38 kg/cm² at 7 days for the 7% dosage (a 1.31-fold increase over the untreated soil) due to dehydration and interparticle polymer network formation. Beyond 7%, strength and compaction declined because the increased polymer volume fraction disrupted the continuity of the mineral soil skeleton. Consequently, the BA–MMA copolymer is an effective low-carbon stabilizer, with 7% established as the optimum dosage.

Keywords

• Low-plasticity fine-grained soil
• Improvement
• Stabilization
• Polymer emulsion
• Unconfined compressive Strength

Main Subjects

• Geotechnics