29Si and 27Al MAS NMR spectroscopic studies of activated metakaolin-slag mixtures

Blending metakaolin with slag in alkali-activated materials represents a promising way to achieve both acceptable engineering properties and durability. Nuclear Magnetic Resonance (NMR) spectroscopy has appeared as a key technique to investigate the structure of alkali-activation products. However, there is not a consensus on the analysis of NMR spectra to identify the phases formed in binary slag-metakaolin mixtures. This paper characterizes the phase composition and the reaction degree of alkali-activated metakaolin-slag blends, with special emphasis on the effect of H2O/Na2O ratio. Different approaches based on the literature are presented and implemented to analyze NMR data. The results suggest the formation of a heterogeneous phase involved in the transformation of 3D network to C-A-S-H. The evaluation of the reaction degree showed that the incorporation of slag in activated metakaolin mixtures resulted in higher reactivity of metakaolin and higher compressive strength.

Automated summary

Blending metakaolin with slag in alkali-activated materials can achieve both acceptable engineering properties and durability. NMR spectroscopy is used to investigate the structure of alkali-activation products, but there is no consensus on the analysis of NMR spectra for identifying the phases formed in binary slag-metakaolin mixtures. This study characterizes the phase composition and reaction degree of alkali-activated metakaolin-slag blends, and shows that the incorporation of slag results in higher reactivity and compressive strength of metakaolin.