Bacterial Concrete: A biological approach to reduced permeability

This paper investigated the effects of Bacillus megaterium (class 1 WHO) ground borne bacteria when introduced into a concrete mix. The range of investigation examined, penetration of water under pressure (permeability) and compressive strength compared against a plain control sample. Three test batches of concrete were cast; plain concrete, concrete with live bacteria including nutrient broth with urea (NBU) and concrete where the mixing water was replaced with nutrient broth with urea. The purpose of the different batches was to establish the effects of Bacillus megaterium and nutrient broth with urea upon cured concrete. The results were compared to a plain concrete control sample and conclusions were drawn. The findings established that, bacterial concrete, when compared to plain concrete, provided increased density and lower permeability, however the bacterial concrete compressive strength, when compared to plain concrete, was impaired due to the introduction of NBU into the concrete mix. This was due to the calcium chloride component of the NBU which can act as an accelerator but has the effect of lowering the final compressive strength. This work contributes to and continues research into applying biological processes to develop more sustainable construction materials.