Effect of aluminate and carbonate in magnesia silicate cement

The effect of alumina and carbonates on magnesium silicate hydrate (M-S-H) cements was investigated at high Mg/Si ratios (1.5–2.5), constant Na2CO3 concentration (17 g/L) Al/Si ratio either 0, 1 or 3.2. Either MgO MgO/hydromagnesite (50/50 wt %) used, as well silica fume, metakaolin amorphous Al2O3. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), 29Si 27Al MAS NMR data showed that M-(A-)S–H phases formed in all cases hydrotalcite presence aluminum. Little hydromagnesite had reacted the 23Na only little sodium sorbed; thermogravimetric coupled with infrared exhaust gas 13 C were incorporated traces carbonate sorbed. Thermodynamic modelling carried out an updated Mg-phases database relatively good agreement phase assemblage observed if reactivity starting materials considered.