Used for determining the passing ability (measured by the blocking step), the flow spread and t500 flow time of the self compacting concrete as the concrete flows through the J-Ring. The apparatus consists of a stainless steel crown with 16 bars 18 mm dia.

J-Ring Test Apparatus(ASTM C1621/C1621M)
1. Scope
This test method covers determination of the passing ability of self-consolidating concrete (SCC) by using the J-Ring in combination with a mold.
2. Apparatus
2.1 J-Ring—The apparatus shall consist of a steel (or equivalent nonabsorbent, rigid material) ring measuring 300mm [12 in.] in diameter at the center of the ring and 25 mm [1in.] in thickness, and sixteen 16 mm [ 5 ⁄ 8 in.] diameter smooth steel rods spaced evenly around the ring measuring 100 mm [4in.] in length (see Fig. 1).

2.2 Mold—The mold used in this test method shall conform to that described in Test Method C143/C143M, except that the foot pieces are removed when the test is performed with the mold in the upright position (Procedure A).
2.3 Base Plate—A nonabsorbent, smooth, rigid plate having a minimum diameter of 915 mm [36 in.].
N OTE 1—Field experience has shown that base plates made from sealed or laminated plywood, rigid plastic, or steel are suitable for performing
this test.
2.4 Strike-off Bar—As described in Test Method C173/C173M.
2.5 Measuring Device—A ruler, metal roll-up measuring tape, or similar rigid or semi-rigid measuring instrument marked in increments of 5 mm [ 1 ⁄ 4 in.] or less.
2.6 Sample Receptacle—A pan or wheelbarrow that is water-tight, has a nonabsorbent surface, and is large enough to allow both remixing of the entire sample and retain a volume of concrete sufficient to fill the mold.
2.7 Pouring Vessel for SCC—Awater-tight container having a volume such that concrete is not spilled during placement in the mold.
N OTE 2—A pouring vessel with a pouring lip is useful in reducing the probability of concrete spilling while filling the mold.
2.8 Other Tools—Items such as shovels and scoops capable of remixing the concrete in the sample receptacle, filling the pouring vessel, or both.
3. Procedure
3.1 Perform this test on a flat, level, nonabsorbent work surface such as a concrete floor or base plate. Use a base plate in conditions where a flat, level surface is not available, such as on a construction site. When the base plate is used, position and shim the base plate so that it is fully supported. Dampen the work surface, removing any standing water. Do not subject the work surface or mold to vibration or disturbance.
3.1.1 When performing the slump flow test for a given study or project, do not change the base plate type for the duration of the study or project.
3.1.2 Place the J-Ring on the work surface or at the center of the base plate.
3.2 Remixing of Sample. Remix the sample, obtained in accordance with 7.1, in the sample receptacle using a shovel or scoop so that the concrete is homogeneous.
3.3 Filling the Mold—Fill the mold by following either Procedure A or Procedure B.
3.3.1 Filling Procedure A (Upright Mold)—Dampen the interior of the mold and place it on the work surface or base plate with the larger opening facing down and concentric with the J-Ring. Hold the mold firmly in place during filling.
3.3.2 Filling Procedure B (Inverted Mold)—Dampen the interior of the mold and place it on the work surface or base plate with the smaller opening facing down and concentric with the J-Ring (see Note 3).
N OTE 3—As a precaution, when filling the mold in the inverted position, the mold may be supported to prevent accidental movement or tipping. Experienced users of this test method have found that it is not necessary to support the mold.

3.3.3 Fill Pouring Vessel—Immediately fill the pouring vessel with a portion ofSCC from the sample receptacle, either by passing the pouring vessel through the concrete or by scooping concrete into the vessel.
3.3.4 Filling Procedure—Immediately fill the mold with SCC by tilting the pouring vessel. Position the lowest point on the rim of the pouring vessel no more than 125 mm [5 in.]above the top of the mold. Ensure an even distribution of concrete, without rodding the concrete or tapping the sides of the mold, while filling the mold.
3.3.5 If necessary, repeat the procedures in 8.3.3 and 8.3.4 until the mold is filled slightly above its rim.
3.4 Strike off the surface of the concrete level with the top of the mold by a sawing motion of the strike-off bar. Remove concrete from the area surrounding the base of the mold to preclude interference with the movement of the flowing concrete. Remove the mold from the concrete by raising it vertically. Raise the mold a distance of 225 6 75 mm [9 6 3in.] in 3 6 1 s by a steady upward lift with no lateral or
torsional motion. Complete the entire test from the start of filling through removal ofthe mold without interruption within an elapsed time of 2 1 ⁄ 2min.
3.5 Wait for the concrete to stop flowing and then measure the largest diameter (j 1 ) of the resulting circular spread of concrete. When a halo is observed in the resulting circular spread of concrete, it shall be included as part of the diameter
of the concrete. Measure a second diameter (j 2 ) of the circular spread at an angle approximately perpendicular to the first measured diameter (j 1 ). Measure the diameters to the nearest 5mm [ 1 ⁄ 4 in.]. Determine the J-Ring flow in accordance with
Section 9.
3.6 If the measurement of the two diameters differs by more than 50 mm [2 in.], the test is invalid and shall be repeated.
3.7 Conduct a slump flow test without the J-Ring in accor-dance with Test Method C1611/C1611M. Use the same filling procedure as used with the J-Ring. Complete the tests with and without the J-Ring within 6 min.

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