Contribution of Recycled Alumina Waste to Cement Strength and Microstructure Development

The role of alumina waste as a reactive pozzolan for the local Portland cement has been thoroughly investigated. The results showed that the initial and final setting times of the hardened blended pastes were reduced significantly by increasing the amount of the added alumina. In addition, the compressive strength and the hydraulic property measures of the hardened blends showed progressive improvement reaching approximately 42% and 23% after the early ages of hydration (1 and 3 days), respectively. According to such conditions, these cement blends could be applied in many concrete applications, such as high speed construction, rapid repair, frost prevention, tunneling, shoring, gas and oil well cementing, that require concrete to have rapid setting and strength development abilities.

The improvement of the physico-mechanical characteristics and the hydration kinetics of the hardened blended pastes with the recycled alumina were explained after the microstructure study included the examinations of hydration product morphology and type, the thermal gravimetric (TG), the differential scanning calometry (DSC) and the differential thermo-gravimetric (DTG) thermographs analyses. The scanning electron microscope (SEM) was used to examine the microstructure and morphology of hydration products.