Confined and unconfined behavior of a silty sand improved by the enzymatic biocementation method

Abstract

The aim of this work is to study the effectiveness of the enzyme-mediated calcium carbonate (CaCO3) precipitation methodology when applied to the confined and unconfined behavior of a silty sand. Based on the analysis of the results of UCS and oedometer tests carried out with non-stabilized and biocemented specimens, the effects of the curing time and the concentration of the biogrout solution (urease, urea, calcium chloride and water) on the improvement of the mechanical characteristics of the treated soils are studied. The results of UCS tests (stiffness and strength) are examined and compared with the results of oedometer tests (compressibility indices and vertical yield stress). The experiments are supplemented with the evaluation of the content of the CaCO3 precipitated, pH value and SEM/EDX tests. The unconfined compressive strength and the yield strength of the biocemented soil increase with the content of CaCO3 precipitated, which is potentiated during a curing time of less than 14 days and for a greater concentration of the biogrout solution. The precipitation of CaCO3 is validated by the results of SEM/EDX tests.