Study of the Pozzolanic Reactivity of Amazonian Metakaolin for Use as a Supplementary Cementitious Material

The application of supplementary cementitious materials (SCMs) as a partial replacement for Portland cement (PC) can significantly reduce carbon dioxide emissions, making the mortar or concrete more sustainable and environmentally friendly. Among the supplementary materials, metakaolin (MK) has received considerable attention, as it provides improvements in mechanical properties and increased durability of the material. The Amazon region presents large deposits of kaolin and therefore this study investigated its use as SCMs. In the study, three metakaolin were produced and characterized using X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XFR), differential thermal analysis (DTA), and laser diffraction techniques. The pozzolanic reactivity study was evaluated by the indirect electrical conductivity method, known as the Luxan Method. In addition, cement pastes were produced, where PC was replaced in the fractions of 40 and 50%, the samples were evaluated by thermogravimetric analysis (TGA) at 28 days of curing. This procedure was adopted to confirm the pozzolanic of MK, by monitoring the reduction of calcium hydroxide. The results show that the wet processing method of kaolin and its calcination at 750 degrees C for 4 h showed satisfactory results, being sufficiently able to eliminate all the calcium hydroxide at 28 days, confirming the pozzolanic test by the Luxan method.