The vulnerability of buildings and structures to rain and flooding due to a lack of adaptive capacity is an issue all over the world. Exploring the bio-resources availability and engineering performance is crucial to increase infrastructure’s resilience. The current study analyses earth-based mortars using mineral precipitation as a biostabiliser (bio) and compares their performance with cement-based mortars. Cultures of S. oneidensis with a concentration of 2.3 × 10⁸ cfu/mL were used to prepare earth-based and cement-based mortars with a ratio of 6% of binder. Microstructure analyses through SEM/EDS, water absorption, moisture buffering, mechanical strength, and porosity are discussed. The biostabiliser decreases water absorption in tidal-splash and saturated environments for earth and cement mortars due to calcium carbonate precipitation. The biostabiliser can prevent water migration more effectively for the cement-based (60% reduction) than for the earth-based mortars (up to 10% reduction) in the first 1 h of contact with water. In an adsorption/desorption environment, the conditions favour desorption in cem+bio, and it seems that the biostabiliser precipitation facilitates the release of the chemicals into the mobile phase. The precipitation in the earth+bio mortar porous media conditions favours the adsorption of water molecules, making the molecule adhere to the stationary phase and be separated from the other sample chemicals. The SEM/EDS performed for the mortars confirms the calcium carbonate precipitation and shows that there is a decrease in the quantity of Si and K if the biostabiliser is used in cement and earth-mortars. This decrease, associated with the ability of S. oneidensis to leach silica, is more impressive for earth+bio, which might be associated with a dissolution of silicate structures due to the presence of more water. For the tested earth-based mortars, there was an increase of 10% for compressive and flexural strength if the biostabiliser was added. For the cement-based mortars, the strength increase was almost double that of the plain one due to the clay surface negative charge in the earth-based compositions.

This paper describes the hygrothermal and mechanical properties and self-healing capacity of a sustainable bio-based mortar repair system for earth construction. There is currently limited characterisation of materials that directly compare earth, bio-fibres and self-healing behaviour. Additionally, the thermal performance of self-healing materials has been under-researched. Both prismatic and 0.1 m × 0.1 m samples were cast with plain mixes, saw mill residue (SMR), straw, wool and wood pellets. Executing both structural and hygrothermal experimentation provided an indication of the performance and durability of the samples. The bio-based agent added to the bio-based composite consisted of bacteria. Adding the bio-based agent to an earth matrix with (wheat) straw, (sheep) wool, SMR and wood pellets showed promising results for the hygric properties, as the initial water adsorption and absorption were lessened. The thermal conductivity was reduced from 0.32 to 0.23 W/m.K when bio-based agents were combined into the earth-based mix design with SMR. Overall, it is evident that out of all ten mix designs, bio-SMR provided the best environmental conditions for the bio-agent.