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<p>Calcium aluminosilicate (CAS) glasses serve as ideal model systems for understanding the composition-structure relationships underpinning the performance of supplementary cementitious materials (SCMs) due to their simpler chemistry and reduced phase heterogeneity. Here, we investigate the structure of a broad compositional range of CAS glasses, including unprecedented high-CaO compositions, using X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy. With increasing CaO content, the XRD hump maxima shifts towards higher diffraction angles and causes downfield shifts in the <sup>29</sup>Si and <sup>27</sup>Al NMR isotropic shift maxima, indicating reduced interatomic distances and decreased electron density around Si and Al nuclei, respectively. These trends, consistent with a depolymerized structure that is more compact and contains a higher number of non-bridging oxygens, also correlate strongly with changes in Si–O-Si and Al–O–Al bond angles predicted by atomistic simulations. FTIR spectra reveals shifts in T-O-T' bond vibrations to lower wavenumbers with increasing CaO, signifying a transition to less polymerized Q<sup>n</sup> (Si, Al) species. Collectively, our results demonstrate the role of CaO in promoting network depolymerization, a crucial factor for SCM reactivity, and provide valuable insights into the structural evolution of CAS glasses as a function of composition.</p>

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Composition-structure relationships for calcium aluminosilicate glasses

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月25日

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  • Subhashree Panda,
  • Meili Liu,
  • Rudra N. Purusottam,
  • Jamie D. Walls,
  • Luis Ruiz Pestana,
  • Prannoy Suraneni

摘要

Calcium aluminosilicate (CAS) glasses serve as ideal model systems for understanding the composition-structure relationships underpinning the performance of supplementary cementitious materials (SCMs) due to their simpler chemistry and reduced phase heterogeneity. Here, we investigate the structure of a broad compositional range of CAS glasses, including unprecedented high-CaO compositions, using X-ray diffraction (XRD), solid-state nuclear magnetic resonance (NMR), and Fourier transform infrared (FTIR) spectroscopy. With increasing CaO content, the XRD hump maxima shifts towards higher diffraction angles and causes downfield shifts in the 29Si and 27Al NMR isotropic shift maxima, indicating reduced interatomic distances and decreased electron density around Si and Al nuclei, respectively. These trends, consistent with a depolymerized structure that is more compact and contains a higher number of non-bridging oxygens, also correlate strongly with changes in Si–O-Si and Al–O–Al bond angles predicted by atomistic simulations. FTIR spectra reveals shifts in T-O-T' bond vibrations to lower wavenumbers with increasing CaO, signifying a transition to less polymerized Qn (Si, Al) species. Collectively, our results demonstrate the role of CaO in promoting network depolymerization, a crucial factor for SCM reactivity, and provide valuable insights into the structural evolution of CAS glasses as a function of composition.