ASTM C234-91a pdf free download.Standard Test Method for Comparing Concretes on the Basis of the Bond Developed with Reinforcing Steel.
ASTM C234-91a covers comparison of concretes on the basis of the bond developed with reinforcing steel.
5. Test Specimens
5.1 The test specimens shall be of two types: one contain ing one reinforcing bar embedded vertically, and the other containing two bars embedded horizontally. Three sped mens of each type shall constitute a set of test specimens.
5.2 Specimens for Vertically Embedded Bar—These specimens shall consist of concrete cubes, 6 in. or 150 mm on each edge with a single reinforcing bar embedded vertically along a central axis in each specimen. The bar shall project downward from the bottom face of the cube as cast a distance of about ¼ in. (10 mm), and shall project upward from the top face whatever distance is necessary to provide sufficient length of bar to extend through the bearing blocks ahd the support of the testing machine and to provide an adequate length to be gripped for application of load (Fig.1).
7. Casting Specimens
7.1 Prior to casting the test specimens, coat the inside surfaces of the molds with a thin film of mineral oil, petroleum jelly, or stearic acid paste. Clean the reinforcing bars of loose rust or scale with a wire brush, and clean ofT oil or grease by washing with a suitable solvent.
7.2 The manner of placing the concrete in the moLds may in some cases be a variable in tests of bond. When this is not the case, use the following procedures for the respective types of specimens (Note 4).
7.2.1 For the 6-in, or 150-mm cubes, place the concrete in two layers of approximately equal thickness and rod each layer 25 times with the 5/ in. (16 mm) diameter tamping rod.
7.2.2 For the 6 by 6 by 12-in, or 150 by 150 by 300-mm prisms, place the concrete in four layers of approximately equal thickness and rod each layer 25 times with the tamping rod (Note 5).

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