Fly Ash and Concrete Durability
P. Klieger and S. Gebler
Appears on pages(s):
air entrainment; alkali-aggregate reactions: concrete durability; deicers; evaluation; fly ash; freeze-thaw durability; sulfate resistance
Concretes containing Class F and Class C fly ashes were evaluated with respect to various aspects of concrete durability. A majority oE concretes with fly ash produced stable air-void systems; however, the volume of air retained over a period of 90 minutes was adversely affected, more in Class F than Class C fly ash concretes. Concretes with fly ash requiring a high dosage of air-entraining admixture generally exhi.bited poor retention of original air content. Organic matter content of the fly ash affected air-entraining admixture dosage and air content stability. Air-entrained concrete with or without fly ash and cured at 73OF (23OC) generally showed good resistance to Ereezing and thawing: however, when these concretes were cured at low temperature, Class F fly ash concretes showed slightly less resistance to freezing and thawing than Class C fly ash concretes. Deicer scaling tests showed that air-entrained concretes without fly ash performed better than fly ash concretes, regardless of curing provided. Both Class C and Class F fly ash concretes exhibited similar performance when subjected to deicer chemicals during freezing and thawing. The chloride-ion penetration of concrete made with fly ash was not signi.Eicantly affected by the class of fly ash. Class F fly ashes were significantly more effective as inhibitors of alkali-silica reaction expansion in mortar bars than were Class C fly ashes. Class F fly ashes significantly improved the sulfate resistance of concrete made with a cement containing 8 % C3A. Concretes with Class C fly ashes exhibited poor performance to sulfate solution.