Effects of Intergrinding Fly Ash on the Sulfate Resistance of Fly Ash Concrete
Reed B. Freeman and Ramon Carrasquillo
Appears on pages(s):
blended cements; chemical attack; durability; expansion; fly ash; sulfate attack; sulfate resistance; Materials Research
The resistance of fly ash concrete to sulfate attack is dependent on both its chemical and physical characteristics. The chemistry and mineralogy of both fly ash and cement influence the sulfate resistance of hydration products, while the permeability of concrete influences the rate of ingress of sulfate ions. Researchers are studying the interdependence of the chemical and physical characteristics of fly ash concrete, as they affect sulfate resistance. Both ASTM Type I and II cements have been partially replaced by both ASTM Class F and C fly ashes. Cement replacement levels of 25 and 35 volume percent have been studied. Fly ashes have been added as mineral admixtures at the concrete mixing stage and interground with the cement constituents, as in blended cement production. Concrete specimens have been monitored for linear expansions and mass changes while immersed in 10-percent sodium sulfate solution. This paper reports on the sulfate resistance of fly ash/Type II cement concrete mixtures after 450 days of sulfate exposure. Data from 57 concrete mixtures are included, 28 of which utilized fly ash/ cement intergrinding procedures.