Early age strength of ambient-cured geopolymer mortars from waste concrete and bricks with different alkaline activators.

Abstract

Background: The dataset in this work emanates from preliminary studies comparing early-age compressive strengths of geopolymer mortars produced from construction and demolition wastes (CDW) commonly found in Qatar using different alkaline activators.  Methods: Waste concrete, waste bricks and steel slag - an industrial waste produced in large quantities in the country - were used as aluminosilicate sources. Waste concrete was used as fine aggregate (75 μm to 4 mm), while solid or hollow red clay bricks were used together with steel slag as aluminosilicate powders. Solid red clay brick (75 μm to 1.4 mm) was also used as fine aggregate in some mixes. Different alkaline activators including solid powder or ground pellet forms of Ca(OH)2, CaO, and Ca(OH)2-NaOH, NaOH-CaCO3 and Na2SiO3-Na2CO3-Ca(OH)2 mixtures were employed by just adding water. A few mixes included both solid powder Ca(OH)2 and viscous solutions of NaOH and NaOH-Na2SiO3 as alkaline activators. The geopolymer mortars also included small amounts of some other additives such as gypsum, microsilica and aluminium sulfate to enhance the geopolymerization and hydration process. Random proportions of the materials were considered in the range-finding experiments, and the mortars produced were tested for compressive strength. Results: The data show the 7-day compressive strengths and densities of the 40 mixtures considered with mostly ambient temperature (20°C) curing. It also shows such data for mixtures in which variables such as curing at 40°C, mixing with hot water at 50 - 60°C temperature, grading of waste concrete aggregates, and collective grinding of the powdered materials were considered. Conclusions: The dataset shows possible early-age compressive strengths of different geopolymer mortar mixture designs and the materials and mixture design methods that can be used to achieve desired early-age strengths from waste concrete and bricks.