Effect of coarse aggregate size on strength and workability of concrete
ABSTRACT The properties of concrete were studied when the proportions of 37.5 and 19.5 mm stone in the coarse aggregate were varied. With the cement content of 160 kg/m3 and the ratio of water/cement (w/c) greater than 0.9, the compressive strength is maximum at 25 percent by weight (w/o) of 37.5 mm stone. Conversely, for the cement content of 350 kg/m3 and w/c ratios of less than 0.50, maximum compressive strength is substantively reduced. For both 160 kg/m3 and 350 kg/m3 cement contents, workability improves slightly as the proportion of the 37.5 mm stone is increased. For 100 mm fixed slumps and cement content of less than 160 kg/m3, there was little change in compressive strength as the proportion of 37.5 mm stone increased. However, when cement content was increased from 190 to 350 kg/m3, maximum compressive strength was observed, which shifted downward from 50 w/o to 25 w/o of 37.5 mm stone. In general, to maintain a 100 mm slump, water demand decreased as the proportion of 37.5 mm stone in the coarse aggregate fraction increased.Key words: concrete, compressive strength, workability, slump, aggregate, size, cement.
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ABSTRACT: To meet the requirement of nonlinear analysis and design for mass concrete structures, the mechanical characteristics of mass concrete specimens 25×25×40cm with three-graded aggregate 5–80mm under biaxial compression-tension and triaxial compression-compression-tension was studied experimentally with the multiaxial concrete apparatus. In comparison with the corresponding wet-screened concrete specimens 15×15×30cm with two-graded aggregate 5–40mm, it was found that the wet-screened effect and size effect under complex stress states were obvious, as under uniaxial stress state. By regression of the tests results, respective failure criteria for mass concrete in principal stress space and octahedronal stress space were proposed.Materials and Structures 01/2009; 42(2):241-249. · 1.18 Impact Factor