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In this paper, two popular measures of workability, namely, slump and V-B time, are compared for plain and steel (hooked) fiber-reinforced concrete. The results are based on experiments made on both types of concrete with and without high-range, water-reducing admixture. The fibers were 50 mm (2 in.) long with deformed ends glued together side by side into bundles (collated) with a water-soluble glue. The W-C ratio varied from 0.3 to 0.62. The air content ranged from 2 to 12%. In terms of workability, the whole spectrum ranging from no slump concrete to flowing concrete was covered.
Based on the results of this investigation, the following general equation can be written relating V-B time and slump
The addition of high-range water reducer and fibers influences the relationship and hence the constants a and b. The slope of the line, b, is highest for plain concrete without high-range, water-reducing admixture and lowest for fiber-reinforced concrete. In the case of plain concrete, the addition of high-range water reducer seems to result in a more cohesive mixture. As a result, V-B times can be recorded for slumps as high as 163 mm (6.4 in.). Without the addition of the admixture, concrete seems to collapse around a slump of 89 mm (3.5 in.). The addition of fibers increases the cohesiveness of the mixture considerably. For fiber-reinforced concrete made using high-range water reducer, V-B time could be measured for slumps as high as 221 mm (8.7 in.). Generally for a given slump, fiber-reinforced concrete has a higher V-B time than plain concretes.
Associate professor, Rutgers University, New Brunswick, NJ
Professor of civil engineering, South Dakota School of Mines and Technology, Rapid City, SD
Stock #: CCA10400J