Volume 2, Issue 7 (July 2005)
Decing Salt-Scaling Resistance: Laboratory and Field Evaluation of Concrete Containing up to 70 % Class C and Class F Fly Ash
Laboratory mixtures, pilot mixtures, and field construction mixtures were made to evaluate salt-scaling resistance of concrete incorporating large amounts of either Class C fly ash obtained from several different sources or Class F fly ash. The laboratory mixtures that incorporated Class C fly ash up to a fly ash to cementitious materials ratio (FA/Cm) of 60 % by mass exhibited very slight to moderate scaling. Results from the pilot mixtures indicate that it is possible to produce structural-grade, salt-scaling resistant concrete using up to 56 % Class C fly ash. Specimens of a field mixture containing 50 % Class C fly ash showed moderate to severe scaling, and specimens of a field concrete with 40 % Class F fly ash showed slight to moderate scaling. These field mixtures exhibited satisfactory salt-scaling resistance in actual pavements. Comparisons of strength and scaling results suggest that it would be beneficial to allow sufficient time for high-volume fly ash concrete to develop strength before it is subjected to salt-scaling actions.