Resistance to Chloride Ion Penetration of Concretes Containing Fly Ash, Silica Fume, or Slag

About the report:

The effects of two pozzolanic admixtures, fly ash and silica fume, and a ground-granulated blast furnace slag on the chloride ion intrusion of concretes prepared with low water-to-cementitious material ratios (w/c) (0.35 to 0.45) were investigated. Each of these supplemental cementitious materials was used with a Type I and Type II cement. A Type III cement was also used to determine possible differences in behavior between this cement and Type II when cured at a range of temperature from 40°F to 100°F. The resistance of these concretes to chloride ion penetration was determined using the rapid permeability test (AASHTO T 277) and the 90-day ponding test similar to AASHTO T 259. Results of the rapid permeability test show that the resistance of concrete to the penetration of chloride ions increases significantly as the w/c is decreased for the same proportion of solid ingredients. Usually, concretes with pozzolans or slag exhibited higher resistance to chloride ion penetration than the control concretes containing portland cement as the cementitious material. Results of the 90-day ponding test, which was conducted with 0.40 w/c concretes only, indicated minimal chloride content at depths below 3/4 in (19 ram) for all the test concretes. A precise correlation of the rapid test for chloride permeability (AASHTO T 277) and the 90-day ponding test with salt solution was not attained, but a general relationship was shown. Strength values for all concretes made with the pozzolans and slag at 90 days were in excess of 5,000 psi (34.5 MPa), which is satisfactory. For the same type and amount .of supplemental cementitious material, strength increased as the resistance to chloride ion penetration increased; but when concretes made with different materials were compared, there was no specific relationship between strength and the results of the rapid test for resistance to chloride ion penetration.

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