Enhancing the Water and Biodegradation Resistance of Biopolymer Stabilised Soils – Design Concepts

Paper i proceeding, 2023

The global soil stabilisation market is forecast to grow to $35 billion by 2027 driven primarily by infrastructure and construction activities and exacerbated by the increasingly urgent need to adapt to climate change, flood risk and sea-level rise. Additionally there is anticipated to be increasing demand for stabilised-earth based building products due to their low carbon impact. Cement and lime are widely used to stabilise soil but suffer from significant carbon and energy costs. Naturally sourced biopolymers are a promising low carbon ‘green’ substitute, achieving higher strength in stabilised soils than cement and at similar cost. However, widespread uptake of biopolymers is impeded by the fact that they typically suffer from (a) poor water resistance and (b) poor resistance to biodegradation over time. This paper presents an overview of design concepts and pilot results from a research study into novel biopolymer treatment processes which are applied at the soil/biopolymer mixing stage with the aim of enhancing resistance to water and biodegradation. The approaches include investigation of (i) acetylation, whereby vulnerable hydrophilic functional groups in the biopolymers are replaced by natural hydrophobic acetyl groups, (ii) binding vulnerable hydrophilic groups to specific inorganic minerals, thereby blocking interactions with water. The study design includes a comprehensive series of laboratory tests guided by detailed characterisation of the underlying chemical binding processes with the aim of involving the addition of only small volumes of natural materials as part of the treatment process.