Four-dimensional X-ray microtomography study of water movement during internal curing

Title: Four-dimensional X-ray microtomography study of water movement during internal curing
Author(s): Dale P. Bentz, Phillip M. Halleck, Abraham S. Grader, John W. Roberts
Paper category : conference
Book title: International RILEM Conference on Volume Changes of Hardening Concrete: Testing and Mitigation
Editor(s): O. M. Jensen, P. Lura, K. Kovler
Print-ISBN: 2-35158-004-4
e-ISBN: 2351580052
Publisher: RILEM Publications SARL
Publication year: 2006
Pages: 11 - 20
Total Pages: 10
Nb references: 17
Language: English

Abstract: 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°C. 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 µm, 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.

Online publication: 2006-07-30
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580052.002