Mechanical Properties of Alkali-Activated Ground Waste Glass–Carbide Lime Blends for Geotechnical Uses

Abstract

The present research aims to evaluate the potential of combining two wastes, finely ground waste glass (GWG) and carbide lime (CL), together with a sodium hydroxide solution (SHS) to form a new material which, when compacted, can develop cementitious properties over time. Such blends have potential application in the construction of stabilized rammed walls, as well as in earthworks such as beds of pipelines, spread footings, fill materials, and generally, as a new material for replacement of geomaterials of inadequate specifications in localized geotechnical works. Blends compacted exclusively with water were also produced in order to understand and differentiate, in a comparative manner, the effects of the addition of SHS on the mechanical, mineralogical, and microstructural properties resulting from alkaline reactions. The effects of the CL content, degree of compaction, and inclusion of a SHS on the evolution of strength and stiffness at 7 and 28 days under controlled curing conditions ($23°\mathrm{C}\pm 2°\mathrm{C}$ and 95% relative humidity) were determined. An original parameter, called the porosity/lime index ($\eta /L_{iv}$ ), was used to normalize the behavior of unconfined compressive strength ($q_u$ ) and shear modulus in small strains ($G_0$ ) of the blends. The results have shown that the GWG-CL blends (compacted with water and SHS) developed an evolution of the mechanical properties over time with increasing CL content and degree of compaction. This results from the reaction between the dissolved aluminosilicates present in the GWG and the calcium (${\mathrm{Ca}}^{2+}$ ) in CL, as a product of the pozzolanic and geopolymerization reactions in a high-alkalinity medium by the addition of CL and SHS, respectively. The formation of stable compounds, hydrated calcium silicate (C─ S─ H) type, analogous to those produced in the hydration processes of portland cement after 28 days of curing in alkali-activated blends with SHS, has been verified. Additionally, correlation equations were established between the mechanical response of the blends and the $\eta /L_{iv}$ index, as a function of the curing time and the type of activating solution, which can be considered as dosage curves for the prediction of a required mechanical response.