Synthesis and characterisation of magnesium silicate hydrate gels

Magnesium silicate hydrate gels (M-S-H) have been prepared by precipitation. The range of gel compositions lie between Mg/Si molar ratios 0.67-1.0. The gels were subject to short cure, approximately 24 h at approximately 22 °C and longer cure, 180 days at 85 °C, following which they were characterised by XRD, FT-IR and solid-state 29Si NMR. Ageing at longer times and higher temperatures somewhat improves the local ordering. The nature of the partially ordered structures is related to those of M-S-H mineral phases. The structures and compositions of M-S-H gels differ from those of C-S-H gels and partly on that account, C-S-H gels contain little magnesium while M-S-H gels in blended cements coexist with C-S-H but contain little calcium.