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Sixteen replacement materials, including representatives of six classes—blast-furnace slag, natural cement, fly ash, volcanic glass, calcined opaline shale, and uncalcined diatomite—were investigated together with five portland cements: two type I cements, of low- and high-alkali content, a type II, a type III, and a type IV. A total of 123 concrete mixtures containing crushed limestone aggregates up to 3/4 in. in size, 6 ± 1/2 per cent air, and having a slump of approximately 21/2 in. were proportioned. About half the mixtures had a water-cement ratio of 0.5 by weight, to represent structural concrete, the remainder, 0.8, to represent mass concrete. The 16 materials were used as partial replacements of the portland cement in various percentages by solid volume from 8 to 70. The performance of the replacement materials in concrete was rated against selected values for certain properties regarded as critical for the two classes of concrete studied. Structural concrete (0.5 water-cement ratio) was regarded as adequate if its bleeding did not exceed 5 per cent, its permeability, Kc, did not exceed 25, its resistance to laboratory freezing-and-thawing (DFE) was at least 60, its shrinkage did not exceed 0.070 per cent at 180 days, and its compressive strength at 28 and 90 days was at least 3000 and 4000 psi, respectively. Mass concrete (0.8 water-cement ratio) was rated against the following factors: bleeding not exceeding 7 per cent, permeability Kc, not exceeding 10, compressive strength at 3 and 90 days at least 500 and 2000 psi, respectively; in addition, credit was given for the degree to which the heat of hydration was reduced by the use of the replacement materials. Structural concrete (0.5 water-cement ratio) made with type II portland cement and having as high a rating as that containing no replacement material was obtained when part of the portland cement was replaced by the following materials in the indicated amounts: 50 per cent slags I and II or natural cement I; 35 per cent natural cements I and II; 30 per cent fly ash I; 25 per cent pumicite I; 20 per cent natural cement I, or calcined shale I; or 8, 12, or 16 per cent uncalcined diatomite. Mass concrete (0.8 water-cement ratio) made with type II portland cement and having a rating as high or higher than that containing no replacement material was obtained when part of the portland cement was replaced by the following materials in the indicated amounts: 50 per cent natural cement I; 40 per cent calcined shale I; 35 per cent natural cement I, pumicite II, or tuff; 30 per cent slag I, calcined shales I and II, or calcined diatomite; 25 per cent pumicite I; 20 per cent natural I, or calcined shale I; and 8, 12, or 16 per cent uncalcined diatomite.
Civil Engineer (Concrete Research), Waterways Experiment Station, Corps of Engineers, U. S. Army, Jackson, Miss.