Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1456743 | Cement and Concrete Research | 2011 | 10 Pages |
The hydration of two slags with different Al2O3 contents activated with sodium hydroxide and hydrous sodium metasilicate (commonly named water glass) is studied using a multi-method approach. In all systems, C-S-H incorporating aluminium and a hydrotalcite-like phase with Mg/Al ratio ~ 2 are the main hydration products. The C-S-H gels present in NaOH activated pastes are more crystalline and contain less water; a calcium silicate hydrate (C-S-H) and a sodium rich C-N-S-H with a similar Ca content are observed at longer hydration times. The activation using NaOH results in high early strength, but strength at 7 days and longer is lower than for the sodium metasilicate systems. The drastic difference in C-S-H structure leads to a coarser capillary porosity and to lower compressive strength for the NaOH activated than for the sodium metasilicate activated slags at the same degree of slag reaction.