A Study of Alkali-Aggregate Reactivity by Means of Mortar Bar Expansion


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Title: A Study of Alkali-Aggregate Reactivity by Means of Mortar Bar Expansion

Author(s): T. M. Kelley, L. Schuman, and F. B. Hornibrook

Publication: Journal Proceedings

Volume: 45

Issue: 9

Appears on pages(s): 57-80

Keywords: no keywords

Date: 9/1/1948

Many types of aggregate were combined in varying amounts and sizes with high- and low-alkali cements and formed in to 1 x 1 x 10-in. mortar bars. The bars were stored either at 70 F or at 100 F and their expansions measured at ages raging from 1 month to 4 years. In combination with high-alkali cements, opal, opaline chert and a siliceous dolomitic limestone were found to cause greatest expansion. Certain aggregates containing volcanic glasses and some natural sands and gravel also caused excessive expansion; with one exception, these sands contained small amounts of opal. Greatly delayed expansion resulted with the very fine sizes of opal, particularly in combination with high-soda cement. Similar behavior resulted with No. 81 size opal and low-alkali cement with either Na2SO4 or K2SO4 additions. Materials such as dehydrated kaolin, soda feldspar, magensium flusilicate, acetic acid and calcium hydroxide added in small amounts as correctives were ineffective. However, diatomaceous earth in sufficient quantity as a cement rplacement eliminated expansion.