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Material Testing

J-Ring Test for Self-Compacting Concrete

Run the J-Ring flow alongside a plain slump flow; a difference under 25 mm means good passing ability, over 50 mm means poor.

Constropedia Editorial First published October 2021 · Updated September 2026 · 3 min read

J-Ring Test

It denotes passing ability of the self compacting concrete. This test method covers determination of the passing ability of self-consolidating concrete by using the J-Ring in combination with a slump cone mold. The test method is limited to concrete with maximum size of aggregate of 25 mm. This test method provides a procedure to determine the passing ability of self consolidating concrete mixtures. The difference between the slump flow and J-Ring flow is an indication of the passing ability of the concrete. A difference less than 1 in (25 mm) indicates good passing ability and a difference greater than 2 in (50 mm) indicates poor passing ability. The orientation of the slump cone for the J-Ring test and for the slump flow test without the J-Ring shall be the same.

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Apparatus

J-Ring – The apparatus shall consist of a steel ring measuring 12 in (300 mm) in diameter at the center of the ring and 1 in (25 mm) in thickness, and sixteen ⅝ in (16 mm) diameter smooth steel rods spaced evenly around the ring measuring 4 in (100 mm) in length.

Mold – The mold (slump cone) used in this test method.

Base Plate – A nonabsorbent, rigid plate having a diameter of at least 36 in (915 mm).

Galvanised slump cone standing upright inside a red J-Ring with numbered steel rods, on a board

Strike Off Bar

Measuring Device – A ruler, metal roll-up measuring tape, or similar rigid or semi-rigid length measuring instrument marked in increments of ¼ in (5 mm) or less.

White slump flow base plate marked with concentric circles and a handle slot

Procedure

  1. Perform the test on a flat, level, and nonabsorbent base plate. Position and shim the base plate so that it is fully supported and level. Pre-moisten the base plate with a damp towel, rag, or sponge. Rest the J-Ring at the center of the base plate.
  2. Filling Procedure B (Inverted Mold) – Dampen the mold, and place it on the base plate with the smaller opening facing down and concentric with the J-Ring. Support the mold and fill the mold in one lift. Heap the concrete above the top of the mold.
  3. 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 mold to preclude interference with the movement of the flowing concrete. Raise the mold a distance of 9 ± 3 in (230 ± 75 mm) in 3 ± 1 s by a steady vertical lift with no lateral or torsional motion. Complete the entire procedure from start of the filling through removal of the mold without interruption within an elapsed time of 2½ min.
  4. Wait for the concrete to stop flowing and then measure the largest diameter (d1) of the resulting circular flow of concrete. When a halo is observed in the resulting circular flow of concrete, it shall be included as part of the diameter of the concrete. Measure a second diameter (d2) of the circular flow at approximately perpendicular to the first measured diameter (d1). Measure the diameters to the nearest ¼ in (5 mm).
  5. Conduct a slump flow test without the J-Ring. Use the same filling procedure as used with the J-Ring. Complete the tests with and without the J-Ring within 6 min.

Calculations

  • Calculate J-Ring flow according to the following equation:
    J-Ring flow = (d1 +d2)/2
  • Calculate the slump flow according to the following equation:
    Slump flow = (d1 +d2)/2
  • Calculate the difference between slump flow and J-Ring flow to the nearest ½ in (10 mm). This number represents the passing ability of the concrete.

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