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Studies of Hydration and Drying in Cement Pastes by Scanning X-Ray Absorptiometry.


pdf icon 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.