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Title: Role of interatomic bonding in the mechanical anisotropy and interlayer cohesion of CSH crystals

Atomic scale properties of calcium silicate hydrate (CSH), the main binding phase of hardened Portland cement, are not well understood. Over a century of intense research has identified almost 50 different crystalline CSH minerals which are mainly categorized by their Ca/Si ratio. The electronic structure and interatomic bonding in four major CSH crystalline phases with structures close to those found in hardened cement are investigated via ab initio methods. Our result reveals the critical role of hydrogen bonding and importance of specifying precise locations for water molecules. Quantitative analysis of contributions from different bond types to the overall cohesion shows that while the Si-O covalent bonds dominate, the hydrogen bonding and Ca-O bonding are also very significant. Calculated results reveal the correlation between bond topology and interlayer cohesion. The overall bond order density (BOD) is found to be a more critical measure than the Ca/Si ratio in classifying different CSH crystals.
Authors:
 [1] ;  [2] ; ;  [1] ;  [1]
  1. Department of Physics and Astronomy, University of Missouri—Kansas City, Kansas City, MO 64110 (United States)
  2. Department of Civil, Environmental, and Architectural Engineering, University of Kansas, Lawrence, KS 66045 (United States)
Publication Date:
OSTI Identifier:
22220814
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 52; Other Information: Copyright (c) 2013 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; ANISOTROPY; BONDING; CALCIUM SILICATES; CHEMICAL BONDS; CRYSTALS; DENSITY; ELECTRONIC STRUCTURE; HYDRATES; HYDROGEN; MECHANICAL PROPERTIES; PORTLAND CEMENT