Study on the hydration product of ettringite in cement paste with ethanol-diisopropanolamine

Ettringite (AFt) is a very important hydration product of hardened cement pastes in the early stage. The effect of ethanol-diisopropanolamine (EDIPA) on the formation and transform process of AFt in cement pastes was systematically investigated in this paper. The results indicate that the AFt content in hardened cement pastes notably decreases due to the inhibition effect of EDIPA on the dissolution of gypsum. In addition, EDIPA promotes the transformation of AFt into calcium monosulfoaluminate hydrate and considerably alters the morphology of AFt crystals from the acicular crystals to stubby rods crystals. The mechanism of the formation of EDIPA-Ca2+ complex by the interaction between Ca2+ in ettringite and the oxygen atoms in EDIPA molecule was proposed. EDIPA-Ca2+ complex can slow down or prevent the crystal growth process of AFt and lead to altering the morphology of AFt crystals.