Experiments and modelling of soil biocementation using the carbonic anhydrase metabolic pathway

Biocementation, i.e., the soil cementation using cements produced biomimetically, has recently been introduced as a method of ground improvement, which is potentially more eco-friendly than conventional ground improvement methods. To date, the vast majority of researchers have used the urea hydrolysis metabolic pathway to biocement soils. We present instead work focusing on a less researched and potentially more interesting pathway, the carbonic anhydrase route, which produces biocement while sequestering CO2. In this paper we present experimental results of bioprecipitate analysis and biocementation using CA producing bacteria; indicative results using the same bacteria though the ureolytic pathway are also shown; their modelling is then discussed instructed by studies on the ureolytic pathway. The results of this study based on bioprecipitate characterisation prove the precipitation of calcium carbonate using the CA pathway. The biocementation by biostimulation of the soil using the CA pathway was also proven, based on the unconfined compressive strengths of the treated soil ranging 0.5-1 MPa depending on cementing solution molarity vs the zero unconfined compressive strength of the untreated soil.