Comparison of 4-1/2- and 7-In. (6-In. Nominal) Maximum Size Aggregate Mixtures for New Lock and Dam No. 26, Mississippi River.

摘要

Three sets of concrete mixtures were proportioned with each of the three water-cement (W/C) ratios: 0.5, 0.7, and 0.8 by weight of cement plus pozzolan. Each set consisted of two mixtures, one containing 4-1/2-in. and the other one 7-in. (6-in. nominal) maximum size aggregate (MSA). The slump of each mixture was 1-1/2 plus or minus 1/2 in., and the air content was 5.0 plus or minus 1 percent on the minus 1-1/2-in. portion of the mixtures. Two batches of concrete were made for each mixture with a 0.7 and 0.8 W/C ratio, and one batch was made for each mixture with a 0.5 W/C ratio by weight. Six- by twelve-in. cylindrical specimens were cast and tested for strength at 28, 90, and 365 days age, and block specimens 3 by 3 by 1.5 ft were made to compare workability.