INFLUENCE OF ALKALI CONTENT OF FLY ASH ON EFFECTIVENESS IN PREVENTING EXPANSION OF CONCRETE.
ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MISS
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Eight mixtures containing various ratios of high- or low-alkali fly ash and cement, and two control mixtures were made to determine the influence of the alkali content of fly ash on its effectiveness in preventing expansion of mortar bars made from the mixtures. Mortar bars were cast and their lengths measured at 2, 14, and 28 days, 6 months, and 1 year. Data from this and a previous investigation using a medium-alkali fly ash indicated that the approximate minimum percentage replacements of portland cement needed to reduce expansion of mortars made with high-alkali cement and very reactive aggregate by 75 at 14 days for the low-, medium-, and high-alkali fly ash are 33, 46, and 47, respectively. The mortar-bar expansion test data were highly variable both within and between batches. Author
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