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Hydration Study of the System Ca 3 Al 2 O 6 –CaSO 4 · 2H 2 O–Ca(OH) 2 –H 2 O with and without Citric Acid
Author(s) -
Singh Nakshatra B.,
Singh Awadhesh K.,
Singh Shashi Prabha
Publication year - 1990
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1990.tb06717.x
Subject(s) - chemistry , ettringite , citric acid , gypsum , diffusion , analytical chemistry (journal) , inorganic chemistry , mineralogy , chemical reaction , cement , materials science , portland cement , thermodynamics , metallurgy , physics , organic chemistry , biochemistry , chromatography
Hydration occurring in the system Ca 3 Al 2 O 6 –CaSO 4 · 2H 2 O–Ca(OH) 2 –H 2 O has been studied at different temperatures and it was found that the reactions are diffusion controlled. The kinetic data obeyed Jander's equation and the rate of reaction increased with increasing temperature. X‐ray diffraction studies and calorimetric measurements show that when gypsum is consumed, ettringite is converted into monosulfate. The rate of this conversion also increased with the increasing temperature and decreased in the presence of citric acid. Spectroscopic studies showed that there was some interaction between citric acid and the cement and that the product of hydration is of colloidal nature. Zeta potential measurements show that retardation of Ca 3 Al 2 O 6 hydration in the presence of gypsum and Ca(OH) 2 is not due to SO 2− 4 adsorption. Electrical conductivity and thermoelectric potential measurements of solid Ca 3 Al 2 O 6 show that Ca 3 Al 2 O 6 is an n ‐type semiconductor and contains defects. The retardation of Ca 3 Al 2 O 6 may be due to poisoning of reaction sites by gypsum and Ca(OH) 2.