Characterization of Spent Bleaching Earth Ash (SBEA) and Assessing Its Use as Partial Cement Replacement in Cement Mortar

Spent bleaching earth ash (SBEA) originates from spent bleaching earth (SBE), which has been shown to possess pozzolanic properties and has been considered for use as cement replacement in various applications such as concrete and masonry. With large amounts of SBEA being produced annually and often treated as hazardous waste, it would be more sustainable to re-use it an application that could reduce the demand on our environment, such as the cement industry investigated in this paper. This paper characterized SBEA in its untreated form and found that it can be classified as a Class N natural pozzolan as defined by ASTM C618 in terms of chemical composition, fineness and water requirement. At the same time, its 7- and 28-day strength activity index both exceeded 75%, further demonstrating its good pozzolanic reactivity. Finally, an assessment of its early (3- and 7-day) and late (28- and 56-day) compressive strengths as well as its flexural strength further reinforces the theory that SBEA could be effectively used as partial replacement of cement in cement mortar applications.