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.