Investigation into Ghanaian calcined clay as supplementary cementitious material

摘要

There is a growing interest on the use of calcined clays as suitable supplementary cementitious materials (SCMs) for construction in recent times. However, the origin of clay presents some form of variations that influences their use as SCM. This study seeks to analyze clay obtained from the Nyamebekyere area of Ghana. The Ghanaian clay was calcined at temperatures of 600, 700, 800, 900, and 1000°C (1112, 1292, 1472, 1652, and 1832°F) in a laboratory furnace. The properties of the raw and calcined clay were characterized using thermal gravimetric analysis (TGA), 27Al and 29Si solid-state magic angle spinning nuclear magnetic resonance (SS MAS NMR), and Fourier transformed infrared (FTIR) spectroscopic techniques. Pozzolanic strength activity indexes (PSAIs) were determined by replacing portland cement with 20% of the calcined materials. The results from the 27Al SS MAS NMR showed that the clay was a 1:1 kaolinitic clay type. The PSAI results were corroborated with the TGA, 27Al and 29Si SS MAS NMR, and the FTIR spectra results to achieve the optimum calcination temperature, which indicated that clay calcined at 800°C (1652°F) attained a more reactive pozzolanic phase that consequently positively influenced the strength activity index. The study recommends calcination temperature of 800°C (1652°F) as the most appropriate temperature for the Ghanaian clay.