Q. We are considering using self-consolidating concrete in bored cast-in-place piles up to 20-m deep. How can we check the level of compaction? Are there clear specifications for testing SCC and test specimens preparation? We cannot locate any ASTM or similar standards or material and workmanship specifications for SCC.

A. Great question. Yes, there are tests that can be used to assess the "level of consolidation" of these mixtures. These methods are being used in various places around the world (mainly Japan and Europe). In addition, ASTM is currently developing the required standards for quantifying SCC behavior, but at present there are no official ASTM standards. Both ACI and PCI also currently have task groups drafting documents for the use of SCC.

Another thing you may want to be aware of is a reference titled, The Effects of Free Fall Concrete in Drilled Shafts by STS Consultants, Northbrook, Ill., sponsored by the International Association of Foundation Drilling. They looked at varying slumps of concrete (maximum being 7 to 8 inches), with the concrete hitting rebar cages on the way down. They drilled an access shaft to actually examine the concrete at depth, and took full length surface cores. The report concluded that, "the free-fall placement method of concrete into properly constructed clean and dry shafts can be performed to depths of 120 feet or greater without meaningful loss of strength or segregation of the concrete aggregate."