Effect of alkalis on fresh C-S-H gels. FTIR analysis

The present study addresses the effect of different concentrations of Na2O on the structure of a composition of fresh C-S-H gels. The gels were synthesized from laboratory reagents, using calcium nitrate as the source of calcium and a sodium silicate solution for the silicon. A 10-M solution of NaOH was used to maintain a pH of over 13 throughout. The synthesized gels were exposed to different amounts of 8-M NaOH to determine their chemical stability and subsequently characterized with Fourier transform IR spectroscopy. The results showed that the addition of different concentrations of sodium leads to C-S-H gel modification even in the very short term. (C) 2009 Elsevier Ltd. All rights reserved.