The structure of alkali silicate gel by total scattering methods

Type
Article

Authors
Benmore, C.J.
Monteiro, Paulo J. M.

KAUST Grant Number
KUS-l1-004021

Date
2010-06

Abstract
The structure of the alkali silicate gel (ASR) collected from the galleries of Furnas Dam in Brazil was determined by a pair distribution function (PDF) analysis of high energy X-ray diffraction data. Since this method is relatively new to concrete structure analysis a detailed introduction on the PDF method is given for glassy SiO2. The bulk amorphous structure of the dam material is confirmed as no Bragg peaks are observed in the scattered intensity. The real space results show that the local structure of the amorphous material is similar to kanemite (KHSi2O5:3H2O) however the long range layer structure of the crystal is broken up in the amorphous state, so that ordering only persists of the length scale of a few polyhedra. The silicate layer structure is a much more disordered than predicted by molecular dynamics models. The X-ray results are consistent with the molecular dynamics model of Kirkpatrick et al. (2005) [1] which predicts that most of the water resides in pores within the amorphous network rather than in layers. The total scattering data provide a rigorous basis against which other models may also be tested. © 2010.

Citation
Benmore CJ, Monteiro PJM (2010) The structure of alkali silicate gel by total scattering methods. Cement and Concrete Research 40: 892–897. Available: http://dx.doi.org/10.1016/j.cemconres.2010.02.006.

Acknowledgements
This work was supported by the U.S. DOE, Argonne National Laboratory under contract number DE-AC02-06CH11357. This publication was based on work supported in part by Award No. KUS-l1-004021, made by King Abdullah University of Science and Technology (KAUST) and by the National Science Foundation grant 062464. R.J. Kirkpatrick is thanked for providing the molecular dynamics simulation data.

Publisher
Elsevier BV

Journal
Cement and Concrete Research

DOI
10.1016/j.cemconres.2010.02.006

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