  Here, an approach to quantify the amorphous-to-disordered/crystalline
transformation occurring in NaOH-activated ground granulated blast-furnace slag
(GGBS) is outlined that combines atomistic modeling with in situ pair
distribution function (PDF) analysis. Firstly, by using force-field molecular
dynamics (MD) simulations, a detailed structural representation is generated
for the amorphous GGBS that is in agreement with experimental X-ray scattering
data. Use of this structural representation along with literature-derived
structures for the reaction products allows for real space X-ray PDF refinement
of the alkaline activation of GGBS, resulting in the quantification of all
phases and the degree of reaction (DOR) as a function of reaction time. All
phases and the DOR are seen to approximately follow a logarithmic-type
time-dependent behavior up to 5 months, while at early age (up to 11 hours) the
DOR is accurately captured by a modified pseudo-single step first-order
reaction model. Lastly, the evolution of DOR is found to agree with several
other complementary in situ data containing quantitative reaction information,
including isothermal conduction calorimetry, Fourier transform infrared
spectroscopy, and quasi-elastic neutron scattering.
