Alkali-activated red ceramic wastes-carbide lime blend: An alternative alkaline cement manufactured at room temperature

Abstract

Alkali-activated cements based on binary, ternary or admixture systems have allowed the inclusion of various wastes and/or low value-added by-products as an alternative for their production. In this work, the alkaline activation, by means of sodium hydroxide solutions, of the combination of low reactivity red ceramic wastes and carbide lime is studied. The performance of the blends was evaluated by uniaxial compressive strength and dynamic Young's modulus tests after curing at ambient temperatures and a short period of time (7 days). From an analysis of variance and a Tukey's post hoc test, it was determined that the treatment corresponding to the red ceramic waste-carbide lime mixture in proportions 70%–30% and an alkali concentration of 4%, was the dose that yielded the best mechanical results. This mixture was analyzed by X-ray diffraction, infrared spectroscopy, and scan electron microscopy. The results show the production of an alternative alkali-activated cement whose performances are associated with the formation of a C-A-S-H and (N,C)-A-S-H gel coexisting in the same cementitious matrix. In addition, increases in mechanical performance of up to 900% are reported in relation to red ceramic waste-based alkaline pastes (treatments without carbide lime) and red ceramic waste-carbide lime mixtures (control pastes - activated exclusively with water) under the same curing conditions, enhancing its viability to be used as a cementitious agent in in-situ construction works, i.e., construction processes where long curing times and the inclusion of thermal curing to consolidate the cementitious reaction products are unfeasible.