Recycling biopolymer stabilised earthen construction materials using β-mannanase

Abstract

Biopolymers like guar and xanthan gums are considered to be sustainable soil stabilisers that can improve engineering properties of earthen construction materials. Recent studies indicate that water-based soil washing has achieved partial success in recycling these materials. In this study, β-mannanase was used in the washing process for recycling. An engineered soil mixture was stabilised using these biopolymers and then recycled in two stages, initially with water and then with β-mannanase. The impact of recycling was ascertained in terms of particle size distribution and Atterberg limits. The recycled soil was subsequently used to produce earthen construction materials, and their mechanical performance was evaluated. Two recycling cycles were conducted to explore the potential of recycling after repeated cycles of biopolymer amendment. Using β-mannanase proved effective in recovering more original material than washing with water and notably more effective for guar gum. Mechanical tests indicated that the recycled material was suitable for earthen construction.