Abstracts Book - IMRC 2018

• SD6-O007 Invited Talk
CEMENT HYDRATION PRODUCTS CHARACTERIZED BY COMBINED
PDF AND RIETVELD ANALYSES
Miguel A. G. Aranda 1 , Ana Cuesta 2 , Angeles G. de la Torre 3 , Isabel Santacruz 3 , Monica Dapiaggi 4
1 ALBA synchrotron, Experiments Division, Spain. 2 Universidad de Málaga, Qumica Inorganica,
Spain. 3 Universidad de Málaga, Departamento de Quimica Inorganica, Spain. 4 University of
Milan, Department of Earth Sciences Ardito Desio, Italy.
There are many commercially important multiphase materials which contain
nanocrystalline/amorphous phases, such as cement pastes, porcelains, glassceramics
or pharmaceutical compounds. The analysis of the atomic ordering in
a nanocrystalline phase with small particle size, below ~5 nm, is intrinsically
complicated because of the lack of long range order. Furthermore, the presence
of additional crystalline phase(s) exacerbates the problem as it is the case for
binders in the construction materials field.
In this communication we will summarize our results for cements pastes based
on using high-resolution synchrotron total scattering data quantitatively
analyzed by Pair Distribution Function (PDF) minimization and Rietveld
methodology to determine phase contents including amorphous and
nanocrystalline fractions. For the PDF data analysis, we have used a multi r-
range analysis approach, where the ~4-7 nm r-range allows determining the
crystalline phase contents; the ~1-2.5 nm r-range is used to characterize the
atomic ordering in the nanocrystalline component; and the ~0.2-1.0 nm r-range
give insights about (possible) additional amorphous components. Specifically,
we have hydrated reference compounds as models for different types of
cements. Hence, monocalcium aluminate, CaAl 2 O 4 , and yeelimite, Ca 4 (AlO 2 ) 6 SO 4 ,
were hydrated as models for calcium aluminate and calcium sulfoaluminate
cements, respectively. Tricalcium silicate, Ca 3 SiO 5 , was hydrated as model for
Portland cement.
The hydration of CaAl 2 O 4 and Ca 4 (AlO 2 ) 6 SO 4 pastes yield aluminium hydroxide
gels. PDF analyses showed that these gels are constituted of nanocrystalline
gibbsite with variable particle sizes that can be as small as 2.5 nm. CaAl 2 O 4
hydrated at 50°C gave crystalline hydrogarnet, Ca 3 Al 2 (OH) 12 , (43 wt%) and
nanogibbsite gel, Al(OH) 3·0.1H 2 O (50 wt%) with a larger average particle size ~5
nm. The hydration of Ca 3 SiO 5 under different conditions, to be described at the
meeting, yielded crystalline portlandite, Ca(OH) 2 and calcium silicate hydrated