Some literature reported that J-ring test for passing ability of self-compacting concrete is the difference between slump flow and J-ring flow diameter, which should normally be within 2 inches (50mm), while,
some literature shows that J-ring test is used to measure the acceptance criteria for the passing ability of cement paste in terms of flow reduction (i.e. difference between slump flow and J-ring flow) and height difference between slump inside and outside J-ring (h2-h1).
Which one is correct? How can one support the results with these?
Thanks.
The real aim of J-ring test is to evaluate if the viscosity of the paste (Water, cement, cementitious material, filler and air) is capable to carry the aggregate particles in the presence of obstacles represented by steel bars.
Taking into account this assumption the most important observation when the concrete has finished to flow is the presence of a peripheral zone without coarse aggregate, if any. If this zone is present, this means the viscosity of the paste is too low to carry properly the coarser sand particles and the coarse aggregates. In other words the past flows faster than the aggregates due to the obstacles represented by the steel bar. As a consequence of this you have both the following situations:
- very high difference between J-ring and slump flow diameters
and at the same time
- difference in height of concrete inside and outside the J-ring.
If the peripheral zone without coarse aggregate is also present in the slump test, resistance to segregation is very poor and consequently even the passing ability.
On the country if the puerperal zone is present only in J-ring test concrete possesses good segregation resistance but poor passing ability.
regards
luigi coppola
The absence of this at the end of the mixture fo the test is
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