Formation of synthetic C-S-H in the presence of triethanolamine and/or polycarboxylate polymers

Abstract

Calcium silicate hydrate (C-S-H) was synthesized by simultaneous feeding Ca(NO3)2 and Na2SiO3 solutions into a bulk solution containing triethanolamine (TEA) or polycarboxylates (PCEs) in order to investigate their impacts on precipitation and structure of the synthetic C-S-H. Evolution of the [Ca] and [Si] in the bulk solution were tracked by ICP-OES and the obtained C-S-H precipitates were characterized by techniques of XRD, TG-DSC, 29Si-NMR, TEM and BET. Results show that the presence of TEA and the PCEs inhibits precipitation of C-S-H as indicated by the notable increases of the saturation index during C-S-H formation. A large amount of the PCEs is incorporated in the obtained C-S-H samples, consequently increasing of calcium to silicon ratio and silicate mean chain length of the C-S-H, reducing the water content of the synthetic C-S-H. Generally, PCE with higher charge density exhibits stronger effects s and TEA displays less influences than the PCEs.