Performance evaluation of clay bio-bricks by different biological treatment methods

To optimise the utilisation of cementation solution and reinforcement effects in clay bio-bricks, this study compared four biological treatment methods: surface alternate infiltration bacterial suspension, surface first infiltration bacterial suspension, surface infiltration combined mixing, and pre-mixing. The performance of these methods was evaluated based on three key metrics: compressive strength, calcium carbonate content, and cementation solution utilisation efficiency. The pre-mixing method exhibited the highest measured compressive strength under the tested conditions. In addition, pre-mixing achieved the highest calcium carbonate content, reached 9.91%. It indicates that pre-mixing promotes a more uniform bacterial distribution within the bio-bricks and maximises utilisation of the cementation solution, reaching 69.6%. In contrast, the surface alternate infiltration method demonstrated the weakest performance, producing only of the calcium carbonate content at 6.93%, with minimal reinforcement and the lowest utilisation rate of only 47.9%. This deficiency was attributed to rapid surface crystal formation, which blocked solution penetration into the interior. Furthermore, compressive strength was greatest when the cementation solution concentration was 0.5 mol/L. Both macroscopic and microscopic analyses indicate that the mechanical performance of clay bio-bricks is closely linked to calcium carbonate content, underscoring the importance of optimising bacterial distribution and solution efficiency.