Q: Does fly ash affect concrete bleeding?

A: A study by the Portland Cement Association compared the bleeding of concretes containing 10 different fly ashes with two control concretes containing no fly ash. In the study, Class C ashes reduced bleeding much more than Class F ashes. The ability to reduce bleeding, for most of the fly ashes, was related to a reduction in the amount of water needed to produce a particular slump.


  • Steven H. Kosmatka, "Bleeding," Significance of Tests and Properties of Concrete and Concrete-Making Materials, STP 169C, ASTM, West Conshohocken, Pa., 1994.
  • Steve Gebler and Paul Klieger, Effect of Fly Ash on Some of the Physical Properties of Concrete, RD089, Portland Cement Association, Skokie, Ill., 1986.