(Received 13 February 2002; accepted 16 June 2003)
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Two cements, with a demonstrated tendency in mortars to suffer expansion related to delayed ettringite formation when cured at high temperatures ≥75°C, were tested after substitution of 5, 17.5, and 30 % with a ASTM C 989 Grade 100 ground granulated blast furnace slag. The two cements are here characterized as a “highly expansive” and a “moderately expansive” portland cement, according to the tendency of each to expand when stored in limewater after curing at elevated temperatures >75°C. Expansion was reduced or delayed, but not eliminated, with 5 % slag substitution, but completely absent when 17.5 % slag substitution was used. Compressive strengths were measured on cubes cured at ambient temperatures and at 90°C. Test results indicated that no strength penalty was experienced in mortars with high slag substitution, cured at 90°C; in fact, the compressive strengths were superior for the 30 % slag mixes, at all ages tested (from 1–28 days of hydration). The conclusion is tentatively reached that the use of blast furnace slag to reduce proclivity to DEF is effective, and does not involve any sacrifice in mortar compressive strength, at least to 28 days of hydration.
Construction Technology Laboratories,
Manager, Quality Assurance, Research and Development, Holcim, Inc., Dundee, Michigan
Stock #: CCA10441J