Premium
Hydration Kinetics and Phase Stability of Dicalcium Silicate Synthesized by the Pechini Process
Author(s) -
Hong SeongHyeon,
Young J. Francis
Publication year - 1999
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.1151-2916.1999.tb01986.x
Subject(s) - calcination , differential scanning calorimetry , thermogravimetry , kinetics , magic angle spinning , silicate , calcium silicate , amorphous solid , mineralogy , materials science , phase (matter) , calcium hydroxide , analytical chemistry (journal) , chemical engineering , calcium silicate hydrate , chemistry , nuclear magnetic resonance spectroscopy , crystallography , inorganic chemistry , cement , chromatography , stereochemistry , organic chemistry , metallurgy , composite material , physics , quantum mechanics , engineering , thermodynamics , catalysis
Reactive dicalcium silicate (Ca 2 SiO 4 ) has been synthesized by the Pechini process, and hydration kinetics studied. With increasing calcination temperature, the amorphous product first crystallizes to α' L ‐phase and subsequently to the ß‐ and γ‐phases. The specific surface area, ranging from 40 to 1 m 2 /g, strongly depends on the calcination temperature of 700°‐1200°C for 1 h. Samples with a high surface area have a high water demand; a water/cement ratio >2.0 is required to produce formable pastes in some instances. Hydration kinetics are determined by XRD, 29 Si magic‐angle spinning nuclear magnetic resonance (MAS NMR), and differential scanning calorimetry/thermogravimetry (DSG/TG). The hydration rate depends only on the surface area, not on the polymorph. Complete hydration occurs in as early as 7 d. Very little calcium hydroxide (Ca(OH) 2 ) is formed in the most reactive specimens (calcined at 700° and 800°C), which indicates the Ca/Si ratio in C‐S‐H gels is ∼2.0, but more Ca(OH) 2 forms from samples calcined at higher temperature. The silicate structure of the hydrated Ca 2 SiO 4 pastes is investigated using 29 Si MAS NMR spectroscopy and trimethylsilylation analysis.