Ten Observations From Experiments to Quantify Water Movement and Porosity Percolation in Hydrating Cement Pastes.
Ten Observations From Experiments to Quantify Water
Movement and Porosity Percolation in Hydrating Cement
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.
cement pastes; experiments; water movement; porosity;
hydration; transport properties; concretes; structures;
x-ray absorption; curing agents; low temperature;
calorimetry; drying; percolation
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.