Synthesis and Morphology of Slag-based Alkali-Activated Materials

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AbstractThe present study focuses on the optimization of alkali activation of ferronickel (FeNi) slag for the production of alkali-activated materials (AAMs). The effect of the main factors including molarity and SiO2/Na2O molar ratio in the activating solution, pre-curing and curing time, curing temperature, and aging period on the compressive strength and other properties of the final products is assessed. Emphasis is paid to the study of the effect of low curing temperature to decrease the overall footprint of alkali activation. Several analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM) are used for the identification of the mineralogy and the morphology of the precursor and the final products. The experimental results indicate that the produced AAMs achieve a maximum compressive strength of 99 MPa using NaOH molarity 8 mol/L (M), SiO2/Na2O molar ratio 1, curing temperature 80 °C, curing time 24 h, and aging period 7 days. SEM/EDS–energy dispersive X-ray spectroscopy analysis indicates that alkali activation results in a homogeneous binding phase, characteristic of the expected iron-rich matrix, while the microstructure of the AAMs is characterized by a glassy and smooth surface without the presence of any visible cracks or defects. The produced AAMs may be used as alternative binders for the replacement of cement in the production of concrete or as construction elements.