Aluminum hydroxide gel characterization within a calcium acuminate cement paste by combined Pair Distribution Function and Rietveld analyses

There are many commercially important multiphase materials which contain amorphous phases, such as cement pastes, porcelains, glass-ceramics or pharmaceutical compounds. However, the analysis of amorphous phase(s) within cement matrices that contain high amounts of crystalline phase(s) is a challenge. Here, we report measurements of total scattering data quantitatively analyzed by Pair Distribution Function (PDF) minimization and Rietveld methodology to determine phase compositions including both amorphous and nanocrystalline phase contents in cement-related samples. Furthermore, laboratory techniques were used to complement the sample characterization. In addition to five reference materials, the main phase of calcium aluminate cements, CaA(12)O(4) hydrated at 50 degrees C to yield crystalline hydrogarnet, Ca3Al2(OH)(12), (43 wt%) and nanocrystalline aluminum hydroxide gel, Al(OH)(3)center dot 0.1H(2)O (50 wt%) was also investigated. The PDF analyses revealed that the hydroxide gel has a gibbsite local structure with an average particle size close to 5 nm. PDF and Rietveld quantitative phase analysis results fully agree. (C) 2017 Elsevier Ltd. All rights reserved.