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Title: Amorphous silica in ultra-high performance concrete: First hour of hydration

Amorphous silica in the sub-micrometer size range is widely used to accelerate cement hydration. Investigations including properties of silica which differ from the specific surface area are rare. In this study, the reactivity of varying types of silica was evaluated based on their specific surface area, surface silanol group density, content of silanol groups and solubility in an alkaline suspension. Pyrogenic silica, silica fume and silica synthesized by hydrolysis and condensation of alkoxy silanes, so-called Stoeber particles, were employed. Influences of the silica within the first hour were further examined in pastes with water/cement ratios of 0.23 using in-situ X-ray diffraction, cryo scanning electron microscopy and pore solution analysis. It was shown that Stoeber particles change the composition of the pore solution. Na{sup +}, K{sup +}, Ca{sup 2+} and silicate ions seem to react to oligomers. The extent of this reaction might be highest for Stoeber particles due to their high reactivity.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [2]
  1. Fraunhofer-Institute for Silicate Research ISC, Neunerplatz 2, 97082 Würzburg (Germany)
  2. (Germany)
  3. Chair for Crystallography and X-ray Methods, Technische Hochschule Nürnberg Georg Simon Ohm, Wassertorstraße 10, 90489 Nürnberg (Germany)
Publication Date:
OSTI Identifier:
22331192
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 58; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCIUM IONS; CEMENTS; CONCRETES; DENSITY; HYDRATION; HYDROLYSIS; PARTICLES; POTASSIUM IONS; SCANNING ELECTRON MICROSCOPY; SILANES; SILICA; SILICATES; SODIUM IONS; SOLUBILITY; SPECIFIC SURFACE AREA; X-RAY DIFFRACTION