Mechanically activated kaolin replacing metakaolin in alkali-activated cement formulation

Abstract

This work provides in-depth research on alkali-activated binder formulations, employing mechanically activatedkaolin (K-MA) as a substitute precursor for metakaolin (MK). The potential of K-MA to replace MK was evaluated byconducting an extensive characterization of the alkali-activated cements (AACs). The structural analysis performedthrough Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA),²⁷Aluminum magic angle spinning nuclear magnetic resonance (²⁷Al MAS NMR), and scanning electron microscopy(SEM) revealed that K-MA enhances the amorphous nature and microstructural homogeneity of cements. The resultsdemonstrated that K-MA-based cements exhibit superior compressive strength than MK-based cements, especiallywhen sodium silicate (waterglass) was added, achieving values up to 42 MPa at 28 days. These findings suggest thatK-MA is a highly effective precursor for AACs formulation, as well as an alternative to replace MK. While thermalactivation (TA) processes for dehydroxylation are associated with significant CO₂ emissions, mechanical activation(MA) offers a more sustainable alternative by utilizing electrical energy, which can be derived from less pollutingrenewable sources.