Abstracts
Expansion of Mortars Cured at Normal and Elevated
By Tennis , Paul D.
Portland Cement Associations
5420 Old Orchard Road
Skokie , IL 60077-1083
PH: 847-966-6200
FAX: 847-966-8389
E-Mail: paul_tennis@portcement.org
Problem Statement
The phenomenon of DEF has received much attention recently and is being cited as a potential cause of deterioration in certain concretes. However, although the levels of alkali, sulfates, aluminates, and other cement characteristics have been correlated with the occurrence of deleterious expansion, there are no quantitative conclusions. For example, high alkali levels and high sulfate levels can lead to high expansions (under certain high temperature curing conditions), but not in all cases. Limits on cement chemistry may incorrectly restrict use of some cements or exclude portland cement concrete from being considered on certain projects. This study is intended to provide data that may be used to determine trends in what combinations of alkali, sulfate, pre-curing time and curing temperature lead to deleterious expansion. Guidance from this work will give users confidence in continuing to use concrete in structures subjected to outdoor exposure conditions.
Research Objectives
The goal of this work is to provide additional data on cement and processing characteristics that may influence DEF. Specifically, the role of sulfates, alkalis, length of pre-curing time, and curing temperature in the expansion of mortars will be examined. Other variables to be examined include: C3A content, cement fineness, type of sand, and storage conditions, including wetting and drying cycles.
Research Method
Mortar prisms fabricated from commercially manufactured cements with a range of chemical and physical properties have been cured at temperatures of 23, 70, 80, and 90 ºC. Sets of these bars have been stored under lime-saturated water at 23 ºC. Selected sets of mortars were also stored under a variety of other conditions. Length changes in the specimens will be monitored for at least three years. Samples undergoing significant length changes will be examined petrographically and by thermal analysis. In addition, mortars prepared using the European EN 196 standard are also being studied.
Product
A technical report will be prepared containing the results of this work. Interim results were presented at the ASTM Symposium on Internal Sulfate Attack, held Dec 1997.
Completion Date: Dec 31, 2001
Category: Materials
Keywords: DEF, expansion, high temperature, mortar,
Date Posted: May 18, 1998
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