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Preparation and characterization of high and low CaO/SiO2 ratio “pure” C–S–H for chemically bonded ceramics

Published online by Cambridge University Press:  31 January 2011

Shiqun Li
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802
Delia M. Roy*
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802
*
a)Also, Department of Materials Science and Engineering.
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Abstract

A type of solidified “pure” C–S–H (calcium silicate hydrate) has been prepared by hydrating mixtures of synthesized Ca3SiO5(C3S) and silica fume at very low water/solid (w/s) ratios (< 0.15). The mechanical properties (splitting tensile strength), stoichiometry, and microstructure of hydration products have been investigated. Results are reported here in which 12.03%−41.56% (by weight) silica fume was added to C3S. It has been found that the strength of the materials with CaO/SiO2(C/S) molar ratio of 1.5 is comparatively higher than that of the others, after curing from 1 day to 28 days. The homogeneity and rheology are of direct importance to the formation of the calcium silicate bonding, which influences greatly the mechanical properties. The hydrates are primarily C–S–H with only small amounts of Ca(OH)2. The compositions of the solidified C–S–H are (1.33–1.37) CaO·SiO2. (1.02–1.21) H2O and (1.40–1.19)CaO·SiO2.(0.68–0.91)H2O for mixtures of C/S = 1.5 and 0.83, respectively. The characterization of the chemically bonded materials by Wn (nonevaporable water), density, x-ray diffraction, and scanning electron microscopy (SEM) studies has been carried out. The relationships between these characteristics and the strength are discussed.

Type
Articles
Copyright
Copyright © Materials Research Society 1988

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