Effect of Organic Matter Content on Enzymatic Biocementation Process Applied to Coarse-Grained Soils

Abstract

This work studies the effect of the organic matter content on the efficiency of the biocementation process due to the precipitation of calcium carbonate (CaCO3) induced by the urease enzyme. Eight different mixtures of an organic soil and a clayed soil are analyzed, which correspond to a range of organic matter content from 0% to 11.3%. The impact of the biocementation process is examined in terms of the strength and stiffness obtained from unconfined compressive strength tests and complemented by measuring the amount of CaCO3 precipitated, pH value, X-ray diffraction (XRD), and scanning electron microscopy (SEM) tests with energy dispersive X-ray (EDX). In general, the biocementation induces an increase in the strength of the material and an increase in the brittleness of the stress-strain behavior. The results also show that the strength gain due to biocementation increases with the amount of CaCO3 precipitate, with greater significance when the content of CaCO3 is lower than 0.5%. The XRD and SEM/EDX tests are coherent with the amount of CaCO3, and both confirm the existence of the precipitation of CaCO3.