Tropical residual soil stabilization: A powder form material for increasing soil strength

- Laterite soil stabilized using a calcium-based additive prepared from biomass silica.
- Stabilized laterite exhibited significant strength gain, even with short curing times.
- Strength gain attributed to formation of calcium aluminate hydrate cementing agents.
- Selected stabilizer appears effective for field treatment of tropical laterite soil.

Stabilization of problematic soils for earthwork applications can be performed using a variety of chemical additives, with lime, cement, or fly ash all being traditionally employed for this purpose. More recently, various new calcium-based additives have been actively marketed by a number of companies for soil stabilization applications. The stabilizing mechanisms of these commercially available products are not fully understood, and their proprietary chemical composition makes it difficult to predict their effectiveness. The current study examines the effectiveness of SH-85, a new calcium-based powder additive which is prepared from biomass silica, for stabilization of a tropical residual laterite soil. At the macro-level, changes in soil strength due to additive stabilization were assessed using a series of unconfined compression strength (UCS) tests. The underlying mechanisms that contributed to the stabilization process were explored using spectroscopic and microscopic techniques, including X-ray diffractometry (XRD), energy-dispersive X-ray spectrometry (EDAX), field emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR). The UCS test results indicated that the addition of SH-85 powder had a significant stabilizing effect on the laterite soil, with the UCS values increasing fivefold after a 7-day curing period. At the micro-level, addition of SH-85 had a weathering effect on the clay minerals, changing the peak intensities of the observed minerals in the XRD spectrums as the stabilized soil was cured. A significant change in the soil fabric was also observed with curing time in the FESEM tests, with additive stabilization yielding a less porous and denser soil fabric, and changes in the surface appearance of treated clay particles. This research study confirms the potential of SH-85 as an alternative to traditional stabilizers for construction involving tropical residual soils.