Internal Curing and Microstructure of High-Performance Mortars

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Title: Internal Curing and Microstructure of High-Performance Mortars

Author(s): D.P. Bentz and P.E. Stutzman

Publication: Special Publication

Volume: 256

Issue:

Appears on pages(s): 81-90

Keywords: blended cement; hydration; internal curing; microstructure; porosity; scanning electron microscopy

Date: 10/1/2008

Abstract:
While typically used to reduce early-age autogenous shrinkage and cracking, internal curing will also strongly influence the microstructure that is produced in cement-based materials. In this paper, the microstructure of a set of three different blended cement high-performance mortars produced with and without internal curing will be compared. For these mortars with a watercementitious material ratio of 0.3 by mass, internal curing has been provided by the addition of pre-wetted lightweight fine aggregates. Their microstructures have been examined after 120 days of sealed curing using scanning electron microscopy of polished surfaces in the back-scattered electron imaging mode. Clear distinctions between the microstructures produced with and without internal curing are noted, including differences in the unreacted cementitious content, the porosity, and the microstructure of the interfacial transition zones between sand grains (normal and lightweight) and the hydrated cement paste. These microstructural observations will be related to previously measured performance attributes such as autogenous deformation and compressive strength development.