Standard operating procedures for biopolymer-treated soils

Growing interest in biopolymer (BP)-based soil treatment (BPST) has highlighted the absence of a unified BP–soil preparation protocol, which continues to drive variability in BPST performance. This paper presents the first comprehensive standard operating procedure (SOP) specifically tailored to preparing BP solutions used in BPST and for other geotechnical and geoenvironmental applications. The proposed SOP provides BP-specific guidance on water quality, pH control, and mixing energy, temperature, and hydration duration for ensuring full polymer activation and obtaining reproducible BP solution properties. The framework integrates rheological measurements, pH control, and ζ-potential analysis for quality control checks. Furthermore, the SOP establishes procedures for incorporating the prepared BP solutions into both mineral soil and alkaline solid waste (e.g. fly ash, cement kiln dust, and steel slags) materials for their stabilisation using the preferred wet-mixing approach. By linking preparation conditions to adsorption mechanisms and composite behaviour, the SOP connects BP chemistry with geoengineering performance. A comparative performance ranking was also introduced, benchmarking commonly used BPs (against a synthetic control) for BPST applications. Overall, the framework enhances reproducibility, strengthens mechanistic interpretation, and supports the scaling of laboratory practices for pilot/field-scale BPST purposes, as well as their uses in other geotechnical and geoenvironmental engineering applications.