Stress-Strain Characteristics and Mineralogy of an Expansive Soil Stabilized Using Lime and Phosphogypsum

Abstract

The study involved the utilization of an industrial waste product, Phosphogypsum (PG) as an additive to lime for the stabilization of soil. Three lime dosages, viz. initial consumption of lime (ICL), optimum lime content (OLC) and less than ICL (LICL) were adopted for stabilizing the soil. The study investigated the stress-strain characteristics of soil composites stabilized with these three lime contents modified with optimum dosages of PG. Mineralogical studies were performed on the spent samples used for a series of determinations of unconfined compression strength tests with various combinations of lime and optimum PG content. The addition of an optimum dosage of PG resulted in an early strength gain of 8.8%, 14.1% and 13.9% and a delayed strength gain of 9.9%, 19% and 19.7% for 3%, 5.5% and 7% for the lime-stabilized soil, respectively. It was found that the addition of PG to the lime resulted in enhanced stiffness, residual strength and reduced brittleness due to the PG amendment of the stabilization reactions. However, in terms of the overall improvement of soil properties, the most favorable benefit was obtained by optimal PG modification of ICL rather than OLC. Microanalysis of the X-ray diffraction scatter also supported the results revealed through stress-strain characteristics. ICL with its optimal PG dosage showed a better progression of pozzolanic reactions when compared to the other two in terms of reduction of peaks of soil minerals and increase in peaks of CSH.

Reusing Dredged Material through Stabilization with So-Called Bio-Enzyme Products

“…These have sometimes been used to enhance the strength of soils because of their cost effectiveness and wide potential applicability; however, the potential of these additives as soil stabilizers remains unclear [30]. While numerous studies have been carried out on the stabilization of different fine-grained soils and sludges using more traditional reagents such as lime, cement, marble powder and other natural and artificial pozzolanic materials [15,16,18,19,[31][32][33][34][35][36], studies on the stabilizer effect of the relatively new bio-enzyme products on soils are much fewer. Research has been conducted on the effectiveness of a fabricated enzymatic delivery system suitable for bio-cementation of soil [37] and efforts have been made to introduce bio-enzyme-based soil stabilization techniques [31].…”