Concerning the article “Specifying Concrete for Performance” in the January issue of Concrete Construction:

This is a somewhat disjointed article that tries to tie several themes together. I want to comment on one section of the article in particular— the reference to the work of Abrams. The statement “Despite the passage of time, these two principles remain unchanged” is simply not technically correct in today's concrete industry. First, because of the use of multiple cementitious materials in the same concrete along with several chemical admixtures, the water-cement ratio is no longer the absolute predictor of concrete performance that it was in Abrams' day. While the w/cm may-give a rough indication of concrete performance, nothing definitive can be said unless the actual components of the concrete are known. Different concretes at the same w/cm may have significantly different properties. Second, the idea that aggregate grading defines water requirements is also outdated. Abrams did not have the vast range of chemical admixtures that are available today. There is no requirement to develop mixture proportions based solely upon the water demands of the aggregates. Water-reducing admixtures are being used to allow work with concretes that have reasonable cementitious materials contents and no slump at all until the chemicals are added.

Finally, encouraging a contractor to use Shilstone's program to tell a producer how to select aggregates would seem to be at the wrong end of the performance versus prescription scale.

— Terry Holland, Concrete Consultant