Three-Dimensional Cement Hydration and Microstructure Program. I. Hydration Rate, Heat of Hydration, and Chemical Shrinkage.
Three-Dimensional Cement Hydration and Microstructure
Program. I. Hydration Rate, Heat of Hydration, and
Bentz, D. P.
NISTIR 5756; 54 p. November 1995.
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
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building technology; cement hydration; chemical
shrinkage; compressive strength; computer models; heat
of hydration; microstructure; non-evaporable water;
A computer program that implements a three-dimensional
model for the microstructural development occuring
during the hydration of portland cement has been
developed. The model includes reactions for the four
major cement phases: tricalcium silicate, dicalcium
silicate, tricalcium aluminate, and tetracalcium
aluminoferrite, and the gypsum which is added to avoid
flash setting. The basis for the computer model is a
set of cellular automata-like rules for dissolution,
diffusion, and reaction. The model operates on
three-dimensional images of multi-phase cement particles
generated to match specific characteristics of
two-dimensional images of real cements. To calibrate
the kinetics of the model, experimental studies have
been conducted at room temperature on two cements issued
by the Cement and Concrete Reference Laboratory at NIST.
Measurements of non-evaporable water content, heat of
hydration, and chemical shrinkage over periods of up to
90 days have been performed for comparison with model
predictions. The measurement of chemical shrinkage is
particularly critical, as it allows an estimation of the
density of the calcium silicate hydrate gel formed
during the hydration to be made. The dispersion models
of Knudsen have been applied in fitting both the model
and experimental data. For the two cements
investigated, it appears that a single function can be
used to convert between model cycles and experimental
time for the three water-to-cement ratios investigated
in this study. This suggests that accurately capturing
the particle size distribution, phase fractions, and
phase distributions of a given cement allows for an
accurate estimation of its hydration characteristics.
Finally, the calibrated kinetic models for the two
cements have been used to successfully predict 7 and
28-day compressive strengths of ASTM C109 50 mm mortar
cubes from 3-day compressive strength data, illustrating
one engineering application for such a three-dimensional
cement hydration and microstructure model.