Moisture-dependent strength and microstructural response of clay stabilized with unsaturated polyester resin

Abstract

This study examines how initial water content influences the strength and microstructural response of a low-plasticity clay stabilized with unsaturated polyester resin (UPR). Clay specimens were prepared at two initial water contents, 0.5 LL and LL, and treated with 0–20% UPR. Unconfined compressive strength (UCS) tests were performed after 14 days of curing, and selected specimens were examined using SEM–EDX, XRD and FTIR. The UCS response depended strongly on initial water content. At 0.5LL, UCS increased with UPR content and reached 9.88 MPa at 20% UPR. At LL, UCS reached a maximum of 5.52 MPa at 10% UPR and then decreased at higher dosages. SEM–EDX observations indicated polymer-rich domains and a more integrated fabric in the 0.5LL specimens, whereas the LL specimens showed a more heterogeneous structure. XRD patterns showed no distinct new crystalline reaction products, and FTIR confirmed a polyester-related ester carbonyl response near 1720 cm⁻ 1 . These results indicate that initial water content strongly influences the efficiency of UPR stabilization in the tested clay–polymer system by affecting the continuity and effectiveness of polymer-associated binding.