Evaluation of the pozzolanic reactivity of two clays from Côte d'Ivoire for substitution of clinker in cement

Abstract

Developing new building materials with low environmental impact is a challenge in the current situation linked to global warming. This study, therefore, contributes to the valorization of local clays as natural pozzolans for the substitution of clinker in cement. Two clays, ME1 and ME2, from the city of Man in the western region of Côte d'Ivoire, which were calcined at 710°C, were used to conduct this study. The chemical analysis of the raw samples by ICP_AES revealed that they mainly comprise three oxides, namely, silica, alumina, and iron, with contents more significant than 70 wt.% of the sum of these three elements. The crystalline phases highlighted by X-ray diffraction showed the presence of quartz, kaolinite, and iron compounds (goethite and hematite) in the raw samples and only quartz and hematite in the calcined samples ME1_710°C and ME2_710°C following the dehydroxylation of kaolinite and goethite. Laser particle size testing highlighted a spread distribution of 3 populations centered at approximately 2, 10, and 39 µm for the raw samples and a single population centered at 39.23 and 133 µm for ME1_710°C and ME2_710°C, respectively. The results of the pozzolanic activity carried out by the saturated lime test showed a significant reactivity for the calcined samples with a Ca(OH)₂ consumption capacity of more than 80 wt.% after 7 days compared to approximately 48 wt.% for the raw samples. The evaluation of the quantities of remaining Ca²⁺ and OH^- ions showed that the concentrations of these two elements were below the solubility curve, indicating good pozzolanic reactivity of the calcined samples.