What is the J-ring test?
The J-ring test is a test on fresh self-compacting concrete (SCC) that measures how well the concrete can flow between reinforcement bars without the coarser material getting stuck. The ring owes its name to its shape: a round steel ring with vertical bars set at regular spacing that imitate the reinforcement.
How does the test work?
The J-ring test is often combined with the slump-flow test:
- The concrete is filled into a cone standing inside the J-ring.
- The cone is lifted, after which the concrete flows out and has to pass through the bars of the ring.
- The diameter of the concrete disc and the height difference of the concrete inside and outside the ring are measured.
A small height difference means the concrete runs well between the bars (good “passing ability”). A large difference shows that the coarse aggregate hangs up at the bars, leading to segregation and voids around the reinforcement.
Why this test?
Self-compacting concrete must de-air and fill completely on its own, without vibration, even in densely reinforced parts. If the concrete blocks at the reinforcement, honeycombing and weak spots form. The J-ring test checks this passing ability and is one of the standard tests for the consistency and workability of SCC, alongside slump flow and the V-funnel. The test is standardised (in the European standard series EN 12350 for testing fresh concrete).
Related terms
- Ready-mix concrete
- Fresh concrete
- Consistency class
- Consistency range
- Compressive strength
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