Effects of Cement PSD on Porosity Percolation and Self-Desiccation.
Effects of Cement PSD on Porosity Percolation and
Self-Desiccation.
(616 K)
Bentz, D. P.
Self-Disiccation and Its Importance in Concrete
Technology, 2nd (Second) International Research Seminar.
Proceedings. June 18, 1999, Lund, Sweden, Persson, B.;
Fagerlund, G., Editor(s)(s), 127-134 pp, 1999.
Keywords:
cements; chemical shrinkage; hydration; interfacial
transition zone; microstructure; particle size
distribution; percolation; self-desiccation; simulation
Abstract:
The degree of self-desiccation in field concrete depends
on the availability of external water to replace that
consumed due to the chemical shrinkage that occurs
during cement hydration. As the cement hydrates, the
capillary porosity depercolates, drastically slowing
down this rate of external water ingress. In this
paper, computer simulations are used to investigate the
effects of cement particle size distribution (PSD) on
capillary porosity percolation and the empty porosity
created by chemical shrinkage. In addition, simulations
are conducted with a single aggregate in the mode1
microstructure to investigate the effects of cement PSD
on interfacial transition zone (ITZ) microstructure at
this aggregate interface. Because the largest pores
empty first during self-desiccation, the ITZ region in
systems containing aggregates is characterized by the
presence of a large volume fraction of empty porosity
relative to that found in the bulk paste. The cement
PSD influences both the volume and size distribution of
empty pores, which will in turn control the internal
relative humidity reduction and autogeneous shrinkage
for these materials. Thus, cement PSD is one material
parameter available for engineering the self-desiccation
and autogeneous shrinkage behavior of low
water-to-cement ratio concretes.
