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A high-pressure X-ray diffraction study of the crystalline phases in calcium aluminate cement paste

  • Author(s): Geng, Guoqing
  • Li, Jiaqi
  • Zhou, Yang
  • Liu, Lin
  • Yan, Jinyuan
  • Kunz, Martin
  • Monteiro, Paulo JM
  • et al.
Abstract

© 2018 Elsevier Ltd Calcium aluminate cement (CAC) has wide application in civil engineering and castable refractory materials. The main binding phases of hardened CAC paste, CaO·Al 2 O 3 ·10H 2 O (CAH 10 ), inevitably converts to 2CaO·Al 2 O 3 ·8H 2 O (C 2 AH 8 ), 3CaO·Al 2 O 3 ·6H 2 O (C 3 AH 6 ) and Al(OH) 3 (AH 3 ), leading to a significant change in the mechanical properties of the CAC matrix. This work investigates the mechanical properties of the main crystalline components in hydrated and/or converted CAC systems, using synchrotron-radiation-based high-pressure X-ray diffraction. The anisotropic deformations of CaAl 2 O 4 (CA), CAH 10 and C 3 AH 6 along each crystallographic direction are investigated, along with their bulk moduli. The density-driven stiffening hypothesis is validated for the studied phases and other cement-based minerals. An atom-scale topological analysis is proposed to explain the unusually high stiffness of CAH 10 . The results provide fundamental information to understand the mechanical properties of single cement-based phases at molecular level, and enable predicting the changing mechanical properties of converted CAC matrix using homogenization models.

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