Curing, Hydration, and Microstructure of Cement Paste.
Curing, Hydration, and Microstructure of Cement Paste.
(2048 K)
Bentz, D. P.; Stutzman, P. E.
ACI Materials Journal, Vol. 103, No. 5, 348-356,
September/October 2006.
Keywords:
cement paste; curing; hydration; microstructure;
porosity; water; cements; low tempeature; calorimetry
Abstract:
This paper compares hydration characteristics and
microstructures of cement pastes with water-cement
ratios (w/c) of 0.35 and 0.435, cured under saturated
and sealed conditions. Degree of hydration is quantified
by loss on ignition (LOI) measurements. The
microstructures, and specifically the pore structures,
of the hydrated pastes are evaluated using scanning
electron microscopy and low temperature calorimetry. The
w/c specimens (equal to 0.35) cured under sealed
conditions first form a depercolated (disconnected)
capillary pore system that later reconnects due to
self-desiccation and autogenous shrinkage. Conversely,
in the w/c specimens (equal to 0.435), there is some
indication that sealed curing actually leads to an
earlier depercolation of the remaining capillary pores
than saturated curing, but without a subsequent
repercolation. The results indicate the criticality of
proper curing for both w/c specimens suggest that curing
for strength and curing for durability may require
different practices and may provide the impetus for
innovative curing strategies to produce concretes with
optimum properties.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899