Influence of slag based pre-geopolymer powders obtained by mechanosynthesis on structure, microstructure and mechanical performance of geopolymer pastes

This work consists of producing a pre-geopolymer powder (PGP) precursor by mechanosynthesis process. Blast furnace slag (BFS) was chosen as an aluminosilicate source and was dry-mixed with sodium silicate and sodium hydroxide microbeads, with different Na2SiO3/NaOH ratios. The mix was subjected to high ball milling, with different milling times and speeds. Several characterization techniques were conducted, including particle size distribution analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mechanical tests. In situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to track the kinetics of the geopolymerization reaction. The results underlined that the elaborated geopolymer pastes structures are mainly amorphous, with the appearance of new structures such as calcium silicate hydrate (CSH), which is formed in parallel with the products of the geopolymerization reaction (N-ASH network). The compressive strength reached 42 MPa after 7 curing days.