Mitigating Metastability of Calcareous Soil Using a Sodium Silicate Solution

Metastable soils have continued to be a bane to civil engineering, causinginfrastructural damages hosted on them and resulting in both economic andlives losses. To mitigate metastability or collapsibility of a calcareous clayeysoil, a suitable sodium silicate solution was formulated under a rigorousprocess in a preliminary investigation to ascertain an optimal solution byaltering silica/sodium ratios and concentrations. However, treatment wasunsuccessful for samples containing greater than 12 % calcite content. Theoptimal solution was then applied in the main study, to treat samples byimpregnation of pre-formed oedometer specimens. Impregnation (a nondestructive means of treatment) was preferred to benefit from the inherentstructural bonding of samples. Oedometer specimens treated were basicallyheat-cured (45 to 50 0C) for twenty-four hours as informed by the preliminarystudy. Collapse potential was estimated by the percentage reduction in heightof a specimen due to wetting at 300 kPa overburden stress. A 5% acidicsolution and distilled water were used as wetting fluids to examine the effectof pore fluid pH on metastability. It was found that at 300 kPa wettingpressure, silicatization (silicate treatment) and heat-curing reduced collapsepotential of samples by 70 % to 78 % under acidic solution wetting and 59%to 73% under distilled water wetting. Therefore, it is concluded that a wellformulated and optimised sodium silicate solution can mitigate metastablecalcareous soils without additives. However, setting of treated samples occursonly after heat-curing.