Research Project C-18 was designed for the purpose of making comparisons of the bond characteristics of commercial and prepared bars of reinforcing steel for horizontal and vertical positions of casting. The data includes tests made for bars cast in concretes of bot low and high slumps. The project was started March 26, 1945, but is not complete to the extent as was originally planned, since only two of the five types of bars employed have been cast in high slump concrete.

The data presented in this report includes test results for eight sets of specimens designated as Series A through Series G, inclusive. Each series consisted of six bars of the same type of deformation, thirty-six inches in length and seven-eighths inches in diameter. The bars were cast in three positions; all embedded in the concrete to depth of 10-1/2 inches (12 diameters), with approximately one-half inch protruding for the purpose of measure the slip at the free end. Of the six bars in each set two were cast in the vertical position in a 6 x 10-1/2 inch cylinder, the bars extending upward, and the remaining four were cast in horizontal positions - two in each of two blocks 6 x 10-1/2 x 18 inches high (See Plate I for a sketch showing the method of casting).

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No. 9

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