Curing and Hydration in Cement - Aluminum Dross Concrete Mortar

Abstract

Cementitious-paste matrix-bond, curing method, and curing period are important factors affecting concrete compressive strength, hence this study focused on the evaluation of the concrete phase transition from the fresh to hardened stage and the characteristics of bond strength of solid objects when aluminum dross (AlDr) is used as partial replacement in cement concrete. Setting times period of AlDr-Cement were examined, and the hydration process commences with adding water to cement to form cement paste until the paste is set and plastic or viscoelastic, in preparation for the curing and hardening process. Similarly, AlDr-Cement mortar (75x75x75mm) cubes were produced and exposed to air, laboratory water, and lagoon water curing for 28 days. Compressive strength tests at 7 days, 14 days, 21 days, and 28 days were performed. Observations indicated that setting time at 10 wt.% gave a better result than the rest with good adhesive binding properties and a setting period of 100 mins between the initial and final setting time of 180 mins. This defines the period for curing and hardening cementitious paste (or solidifying). The paste became set through a chemical reaction of cement with moisture known as the hydration process. The mechanism entails the formation of Calcium Silicates hydrates and Tricalcium Aluminate hydrate as product and with time produces a solid and hard mass that binds aggregates in concrete. Compressive strengths were 8N/mm2 max (0 wt.% AlDr) at 28 days air curing, 9.78N/mm2 max. (10 wt.% AlDr) at 28 days of water curing and 6.67N/mm2 max. (15 wt.% AlDr) at 21 days lagoon water cured. It was also identified that partial addition of AlDr replacement of cement is pozzolanic, with the conclusion that 10 wt.% AlDrCement is adequate for concrete mortar applications.