- Author
- Bentz, D. P. | Halleck, P. M. | Grader, A. S. | Roberts, J. W.
- Title
- Four-Dimensional X-Ray Microtomography Study of Water Movement During Internal Curing.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD Pennsylvania State Univ., University Park Northeast Solite Corp., Richmond, VA
- Book or Conf
- Volume Changes of Hardening Concrete: Testing and Mitigation, International RILEM Conference. Proceedings. August 20-23, 2006, Bagneux, France, Jensen, O. M.; Lura, P.; Kovler, K., Editors, 11-20 p., 2006
- Keywords
- water movement | curing agents | x ray microtomography | effectiveness | cement pastes | cements | hydration | water supply | oxygen index | shrinkage | calorimetry | x ray absorption
- Identifiers
- lightweight aggregates (LWA); superabsorbent polymers (SAP)
- 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.