Peculiarities of hydration of cement paste with addition of hydrosodalite

A synthetic zeolite – hydrosodalite was used as a hydraulic additive for hardened cement paste, and the influence of this additive on the hydration and other properties of the system was determined. Hydraulic activity of zeolite has been examined, X-ray diffraction, DTA and IR analysis of the hardened cement paste with zeolite additive have been carried out. The results have shown that the additive has a high hydraulic activity (the content of bound CaO – 370 mg/g). The addition of hydrosodalite reduces the content of Ca(OH)2 in hardened cement paste which transforms into calcium zeolite – gismundite. The density of the hardened cement paste with the addition of hydrosodalite after 3, 7 and 28 days of curing decreases by about 11%. This predetermines a decrease in the compressive strength of the hardened cement paste. The compressive strength after 3 days of curing decreases by about 70%, after 7 days of curing – by 66%, and after 28 days of curing – by about 65%.