Biomimicry in construction: Glycoprotein-stabilised adobe bricks for enhanced compressive strength inspired by termites mounds

Abstract

Earth is a green building material with very low embodied energy and almost zero greenhouse gas emissions. However, it lacks strength and durability when used without stabilisation. By incorporating responsibly sourced stabilisers, it is possible to enhance the strength of this material. In this study, adobe bricks stabilised using bio-inspired stabilisers were investigated. This research was inspired by the high strength and durability of termite mounds, exploring the stabiliser behind such robust natural constructions. Termites build their mounds by incorporating a glycoprotein from their saliva to cement the sub-soil particles together. Biomimicry has been employed to investigate the potential use of the termites' construction stabiliser in adobe bricks. Three glycoproteins from meat and fish industry waste were identified as potential stabilisers in adobe bricks. Bovine serum albumin (BSA) from cows' blood, mucin from the porcine stomach, and gelatine from cold-water fish skin were the three stabilisers used in this study. Two soils were used to prepare adobe bricks for testing. The primary soil used in this study was from Devon in the United Kingdom (UK). The second soil was obtained from the Mayo neighbourhood in Khartoum, Sudan, and used only in key tests. Adobe bricks were made and stabilised with different concentrations of these bio-inspired stabilisers. Controlled unstabilised adobe bricks were used for comparison. The bricks were tested for their unconfined compressive strength. The main conclusion of this study is that BSA has proven its potential to be used as a stabiliser in earth construction. Using 0.5 % BSA resulted in a 17 % and 41 % increase in the unconfined compressive strength of the British and Sudanese adobe bricks, respectively. In addition, using 5 % BSA resulted in a 203 % and 97 % increase in the unconfined compressive strength of the British and Sudanese adobe bricks, respectively. The compressive strength of BSA-stabilised adobe bricks is higher than that of earth bricks stabilised using 5 % cement and 5 % lime reported in the literature. Furthermore, the compressive strength of the 5 % BSA-stabilised adobe bricks is higher than the lower recommended compressive strength for the hollow concrete blocks in the UK. Hence, these BSA-stabilised adobe bricks could substitute hollow concrete blocks to construct internal walls. The other stabilisers tested did not significantly improve the unconfined compressive strength of the adobe bricks. The study underscores the value of biomimicry and proposes glycoproteins as viable natural stabilisers in earth construction, with further recommendations for in-depth research to optimise application methods and formulations.