Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement

• Published in: Applied sciences Vol. 12; no. 21; p. 10751
• Main Authors: Babafemi, Adewumi John, Knobel, Hendrick, Kolawole, John Temitope, Oyebanjo, Olaonipekun Moses, Bukalo, Nenita Ntumba, Paul, Suvash Chandra, Miah, Md Jihad
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-11-2022
• Subjects: Aluminum oxide; Cement; Clay; Clay minerals; Clinker; Compressive strength; Fruits; Geology; Gypsum; Hydration; Investigations; Kaolinite; Limestone; limestone calcined clay cement; Microstructure; Mineralogy; morphology; Porosity; Portland cement; Portland cements; Roasting; Silicon dioxide; Sustainability; South Africa
• ISSN: 2076-3417; 2076-3417
• DOI: 10.3390/app122110751

Limestone calcined clay cement (LC3) has considerable potential for large-scale implementation. We investigated three selected kaolinitic clays at different locations in South Africa. LC3 mortars were compared to Portland cement mortar as control, particularly the hydration phase mineralogy/content, microstructure, compressive strength, and 3D void structure. The investigation indicated that similar pozzolanic oxide (SiO2 + Al2O3) could be obtained from calcined clay of varied kaolinite content. While kaolinite content improves the pozzolanic activity, consistency, and compressive strength of the mortar, the void refinement at the microscale depends on the degree of limestone filling/hydration. The hydration phase contents, microstructure, mineralogy, and porosity of the processed kaolinitic clays were determined to be adequate. However, it is noted that the intrinsic content of limestone (and gypsum) in commercially available Portland cement should be considered for equivalent clinker, limestone, and gypsum contents of 50%, 15%, and 5%, respectively.