Four-Dimensional X-Ray Microtomography Study of Water Movement During Internal Curing
Dale P. Bentz, P M. Halleck, A S. Grader, J W. Roberts
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 30 oC. A four-dimensional data set is created by obtaining three-dimensional 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 m, 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.
Proceedings of the RILEM Internal Curing Committee Conference
, Halleck, P.
, Grader, A.
and Roberts, J.
Four-Dimensional X-Ray Microtomography Study of Water Movement During Internal Curing, Proceedings of the RILEM Internal Curing Committee Conference, Denmark, SW, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860653
(Accessed June 10, 2023)