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Ten Observations From Experiments to Quantify Water Movement and Porosity Percolation in Hydrating Cement Pastes.


pdf icon Ten Observations From Experiments to Quantify Water Movement and Porosity Percolation in Hydrating Cement Pastes. (2487 K)
Bentz, D. P.

Transport Properties and Concrete Quality Workshop. Materials Science of Concrete Special Volume. Proceedings. October 10-12, 2005, Tempe, AZ, John Wiley and Sons, Inc., NY, Mobasher, B.; Skalny, J., Editor(s)(s), 3-18 pp, 2005.

Keywords:

cement pastes; experiments; water movement; porosity; hydration; transport properties; concretes; structures; x-ray absorption; curing agents; low temperature; calorimetry; drying; percolation

Abstract:

The transport properties and durability performance of concrete structures are both strongly influenced by the three-dimensional microstructure that is established during early age placement and curing. This paper will present observations from two experimental techniques that have been applied to examining this early age microstructure development. First, x-ray absorption measurements are applied to study water (and cement particle) movement during settlement, drying, and curing. Five observations from a series of experiments conducted on single layer and bilayer composite specimens are presented and supported by experimental data. The influences of curing conditions, water-to-cement mass ratio (w/c), cement particle size distribution, shrinkage-reducing admixtures (SRAs), and internal curing via the addition of saturated lightweight aggregates (LWAs) are highlighted. Second, low temperature calorimetry (LTC) is utilized to examine the depercolation/repercolation of the capillary pores in a hydrating cement paste as a function of w/c, curing temperature, and the addition of various alkali ions or an SRA. Once again, five observations from this second type of experiment are presented and substantiated with experimental data. The ten observations have numerous implications for concrete curing practices, possible new applications for existing admixtures, and durability performance of field concrete.