Engineering and Technology Journal Vol. 39, Part A (2021), No. 02, Pages 206-213 Engineering and Technology Journal Journal homepage: engtechjournal.org 206 Publishing rights belongs to University of Technology’s Press, Baghdad, Iraq. Thermally Activated Bentonite As a Supplementary Cementitious Material – A Review Amer A. Al-Hammood a* , Qais J. Frayyeh b , Waleed A. Abbas c a Civil Engineering Dept., University of Technology, Baghdad, Iraq, 42402@student.uotechnology.edu.iq b Civil Engineering Dept., University of Technology, Baghdad, Iraq, 40012@uotechnology.edu.iq c Civil Engineering Dept., University of Technology, Baghdad, Iraq, 40017@uotechnology.edu.iq *Corresponding author. Submitted: 09/06/2020 Accepted: 07/10/2020 Published: 25/02/2021 KEYWORDS ABSTRACT Bentonite, natural pozzoplan, mineral admixtures, supplementary cementitious materials, calcined clay, durable concrete Bentonite is a mixture of clay and non-clay minerals. Montmorillonite clay mineral is a dominant mineral in bentonite. Silica and alumina bond in the crystal structure of montmorillonite. Therefore, they cannot contribute to the pozzolanic reaction. Heat treatment of bentonite leads to the destruction of the crystal structure of montmorillonite and converting silica and alumina to reactive phases. Thermally activated bentonite (TAB) is a relatively low reactive pozzolan when used as partial replacement of Portland cement modifies both fresh and hardened properties of cement paste, mortar, and concrete. The most desired effects of TAB are: improve segregation resistance, reduce the rate of strength gain, and enhance concrete durability against sulfates, chlorides, and acids, in addition to economic and ecological beneficiations. This paper provides information related to heat treatment of bentonite clays and montmorillonite minerals, and their effects on the paste, mortar, and concrete when used as a partial replacement of Portland cement. How to cite this article: A. A. Al-Hammood, Q. J. Frayyeh, and W. A. Abbas, “Thermally Activated Bentonite As a Supplementary Cementitious Material – A Review,” Engineering and Technology Journal, Vol. 39, Part A, No. 02, pp.206-213, 2021. DOI: https://doi.org/10.30684/etj.v39i2A.1733 1. INTRODUCTION The primary sources of supplementary cementitious materials (SCMs) are: naturally formed materials such as volcanic materials and diatomaceous earth, and by-products or wastes from some industries such as fly ash, silica fume, and blast furnace slag. Unfortunately, these sources are available in limited areas. Moreover, the increasing demand for SCMs necessitates investigation for