Effect of Soil Type on the Enzymatic Calcium Carbonate Precipitation Process Used for Soil Improvement

Abstract

This work analyzes the effect of soil type on the process of enzymatic calcium carbonate (CaCO3) precipitation. This methodology is tested for the stabilization of five soil types (poorly graded sand, two silty sands, a silty soil, and an organic soil) in order to examine the impact on strength and stiffness, based on the results of unconfined compression strength (UCS) and scanning electron microscopy (SEM) tests. The results of the UCS tests show that, in the case of the sandy and silty soils, the process of enzymatic calcium carbonate (CaCO3) precipitation potentiates the strengthening of the soils while, in the organic soil, a detrimental biostabilization impact is obtained. The SEM tests show the existence of vestiges of calcium in all the soils, which is a sign that the precipitation of CaCO3 does in fact occur but with a different impact on the strengthening for each soil type. The results suggest that the low pH value of the organic soil, combined with its organic coating of the soil particles, are the key factors that explain the inefficiency of the biostabilization process concerning this type of soil.