Cement Hydration: Building Bridges and Dams at the Microstructure Level.
Cement Hydration: Building Bridges and Dams at the
Microstructure Level.
(437 K)
Bentz, D. P.
Advanced Cement-Based Materials: Research and Teaching.
Knud Hojgaard Conference. Proceedings. June 12-15,
2005, Lyngby, Denmark, Jensen, O. M.; Geiker, M.; Stang,
H., Editor(s)(s), 135-146 pp, 2005.
Keywords:
cements; hydration; bridges; dams; construction;
computer models; cement pastes; computer programs;
solids; curing agents
Abstract:
The concurrent goals of cement hydration are to
percolate (bridge) the original cement particles into a
load-bearing network and to depercolate (dam) the
original water-filled capillary porosity. The initial
volume, particle size distribution, and
flocculation/dispersion state of the cement particles
have a large influence on both hydration rates and
microstructure development. Likewise, the capillary
porosity as characterized by its pore size distribution,
percolation state, and saturation state also influences
both hydration kinetics and microstructure. In this
paper, experimental techniques and computer modeling are
applied to further understanding several of the critical
connections between these physical parameters and
performance properties. First, the setting or bridging
process is explored via a combination of needle
penetration and rheological measurements, in concert
with three-dimensional microstructural modeling. Second,
low temperature calorimetry is shown to be a valuable
indicator of the percolation state or damming of the
water-filled pores with various size entryways in the
three-dimensional microstructure. Porosity percolation
(or depercolation) is shown to be strongly influenced by
both curing conditions and the alkali content of the
cement pastes. Finally, it is proposed that future
efforts in this field be directed towards a greater
understanding of the (nano)structures of cement
hydration products, particularly the calcium silicate
hydrate gel, and their influence on performance
properties.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899