Editor's note: Two readers responded to recent articles on self-consolidating concrete (SCC).

The article ("The SCC Test: Inverted or Upright?" July 2003, p. 34) is interesting, but it misses two much more important points--what does this test purport to tell the user and how do the results relate to the flow of concrete in an actual placement?

My experience is that concrete from the same producer with very similar flow values (+/- 1 inch) can behave very differently in place, ranging from being truly self-compacting to non-moving. Concrete from different producers using different materials and chemical admixtures can have the same flow values and yet behave dramatically differently in place. Do we need another test to allow rejection of concrete when the test doesn’t tell us much about the material?

Our industry likes a test like slump flow (however the cone is oriented) because it is easy to perform and gives a readily measurable result. What we really need is a test for acceptance of concrete that gives a meaningful result and is easy to perform in the field. Development of such a test will help SCC achieve its real potential in the ready-mixed concrete market.

T. C. Holland
Consulting Engineer
Mantua, Ohio