Rheological properties and hydration behavior of portland cement mortars containing calcined red mud

Abstract

Red mud (RM) is a solid waste derived from processing bauxite ore to produce alumina and is considered a hazardous waste due to its high pH. This paper describes the use of untreated mud and after calcination at distinct temperatures (450, 650, and 1000 °C) to attempt to improve its reactivity in cement mortars. In the formulations, portland cement was replaced with up to 30 wt% red mud, and the addition of the red mud changed the hydration process, setting time, and workability. The temperature of hydration increased as more RM was added, particularly when calcined in the interval of 450–650 °C. In these conditions, the hydration process was accelerated, and the workability decreased. These findings indicate that the presence of red mud significantly altered important properties of portland cement.