Studies of Hydration and Drying in Cement Pastes by Scanning X-Ray Absorptiometry.
Studies of Hydration and Drying in Cement Pastes by
Scanning X-Ray Absorptiometry.
(686 K)
Bentz, D. P.; Hansen, K. K.
Water in Cement Paste and Concrete Hydration and Pore
Struture Workshop. Proceedings. Nordic Concrete
Federation. October 7-8, 1999, Skagen, Denmark, 107-114
pp, 1999.
Keywords:
cement paste; drying; x ray absorptiometry; hydration
Abstract:
Hydration and drying in cement pastes are studied using
the X-ray environmental chamber at DTU. By using the
X-ray detector to detect changes in internal density
(indicative of drying), the influence of w/c ratio on
drying during hydration is quantitatively examined. The
proper curing of field concrete is critical to obtaining
optimum performance. This is particularly true from a
durability standpoint since it is the top layer of the
concrete that provides the first protective barrier
against the ingress of deleterious substances. In
current standards, recommended curing practices are
given that depend on the external environment but
generally do not consider the differences in concrete
mixture proportions. Many years ago, Powers suggested
that concrete need only be cured until the capillary
pore system de-percolates. The lower the w/c ratio, the
sooner this de-percolation will occur in the hydration
process. The capillary pore structure in a low w/c ratio
high performance concrete is different from that in a
conventional 0.5 w/c ratio concrete. Hydration and
drying in cement pastes are studied using the X-ray
environmental chamber at the Technical University of
Denmark (DTU). By using the X-ray detector to detect
changes in internal density (indicative of drying), the
influence of the w/c ratio on drying during hydration
can be quantitatively examined.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899