Four-Dimensional X-Ray Microtomography Study of Water Movement During Internal Curing.
Four-Dimensional X-Ray Microtomography Study of Water
Movement During Internal Curing.
Bentz, D. P.; Halleck, P. M.; Grader, A. S.; Roberts, J.
Volume Changes of Hardening Concrete: Testing and
Mitigation, Internaitonal RILEM Conference.
Proceedings. August 20-23, 2006, Bagneux, France,
Jensen, O. M.; Lura, P.; Kovler, K., Editor(s)(s), 11-20
water movement; curing agents; x ray microtomography;
effectiveness; cement pastes; cements; hydration; water
supply; oxygen index; shrinkage; calorimetry; x ray
While the effectiveness of internal curing has been
verified via a variety of experimental measurements,
including internal relative humidity, autogenous
shrinkage, restrained shrinkage, strength development,
and degree of hydration, a direct observation of water
movement during internal curing in four dimensions
(three spatial dimensions and time) has been lacking.
X-ray microtomography offers the possibility to
dynamically monitor density changes in a material,
during its curing process, for example. In this paper,
this technique is applied to monitoring water movement
from saturated lightweight aggregate particles to the
surrounding hydrating cement paste in a high performance
mortar mixture over the course of the first 2 d of
hydration at 30DGC. A four-dimensional data set is
created by obtaining threedimensional image sets on a
single specimen after various hydration times, from just
after mixing to after 47 h of hydration, with a voxel
dimension of less than 20 mm, allowing a clear
delineation of individual lightweight aggregate
particles and much of their internal porosity. Many of
the changes in local density, corresponding to water
movement, occur during the first 24 h of hydration,
during the acceleratory period of the cement hydration
reactions. The four-dimensional data set is processed
and analyzed to quantitatively estimate the volume of
internal curing water that is supplied as a function of
hydration time. These microtomography-based observations
of water movement are supported by more conventional
measurements of hydration including non-evaporable water
content via loss-on-ignition, chemical shrinkage, and
heat of hydration via isothermal calorimetry.