Mechanical response and biodegradation of CMC-modified loam under constant-volume conditions during saturation

Chair of Soil Mechanics, Foundation Engineering and Environmental Geotechnics, Ruhr-University Bochum, Bochum, Germany

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

The use of water-soluble biopolymers as a sustainable alternative to conventional soil improvement in geotechnical engineering is gaining increasing attention. Their mechanical behaviour strongly depends on the degree of saturation: while biopolymer-treated soils may behave in a brittle manner at low water contents, high saturation levels promote biopolymer swelling and the formation of viscoelastic gel structures. Despite their relevance, saturation-dependent responses and polymer-soil interaction mechanisms are not yet sufficiently understood. This study investigates the biopolymer carboxymethylcellulose (CMC) with varying chain lengths and degrees of ^*substitution, applied to a low-plasticity clay. Specimens were compacted to maximum dry density to reflect practical geotechnical boundary conditions. The evolution of total vertical stress was monitored under constant-volume conditions during saturation over a period of approximately 70 days. Potential biodegradation of the biopolymer during testing was assessed using loss-on-ignition (LOI) measurements and rheological analyses performed before and after hydro-mechanical loading. The results indicate that both the mechanical response and biodegradation behaviour of CMC-modified soils are strongly coupled and primarily governed by soil fabric, polymer-soil binding mechanisms, water uptake capacity, and biopolymer composition.