The Influence of some calcined clays from Nigeria as clinker substitute in cementitious systems

This paper examines the possibility of the use of some clays calcined from Nigeria as partial substitutes for clinker in the production of Limestone Calcined Clay Cement (LC3). The clays were calcined in the oven at a temperature of 800 degrees C and for one hour. Dehydroxylation of raw and calcined clays with TGA were carried out between 400 degrees C and 650 degrees C after which the materials were again characterized with XRD. The R-3 pozzolanic test was then carried out to evaluate the reactivity of calcined clays based on the heat release at 24 hours of a model system of portlandite, calcined clay and limestone with adjusted sulfate and alkali content. After the characterization, two clay samples were deemed fit for use as partial replacement of cement because they contain more than 30% kaolinite content. Concrete cubes prepared with the cementitious blends (PC, LC3-50A, LC3-50D and LC3-35D) were cast for mechanical and durability tests, while mercury intrusion porositometry (MIP) was used to determine the porosity of the cementitious blends. The results showed that LC3-50D with about 50% kaolinite content gave the best mechanical and durability results followed by LC3-50A and whereas, LC3-35D containing only 35% cement can still be used for good construction which is a demonstration of the advantage offered with the use of LC3 in cementitious systems. (C) 2020 Published by Elsevier Ltd.