Is there any truth to the allegation that fly ash concretes are less durable to freezing and thawing? Most authorities seem to agree that it is mainly the air void system that assures durability.
A number of investigators have concluded that concretes made with fly ash have lower durability. Erlin and Hime Associates at Northbrook, Illinois attribute this lower durability to the failure to incorporate enough air into fly ash concretes ( Journal of the American Concrete Institute, November 1975, page 648). They say that most fly ashes, because of their carbon content, decrease the efficiency of air entraining agents and that as much as 5 times as much air entraining agent may be needed when fly ash is used. Thus the problem is basically one of mix proportioning rather than use of fly ash and is not insurmountable.