Use of Supplemental Cementitious Materials for Optimum Resistance of Concrete to Chloride Penetration

About the report:

This study was conducted to determine whether significant improvements could be achieved in the resistance to the penetration by chloride ions of concretes with fly ash or slag by the addition of silica fume with either Type II or Type III cement and whether early strengths of concretes with fly ash or slag could be improved by the addition of silica fume. The chloride permeability was estimated by means of AASHTO Test Method T 277. The results show that lower permeability is attained by the addition of silica fume in amounts equal to 5 percent of the cementitious material in both fly ash and slag concretes. There were significant differences between results for specimens moist cured 1 day and 14 days, but with specimens made with Type III cement, even the 1-day moist curing provided low chloride permeability. Silica fume also increased the strength of similar concretes to some degree, but generally, this increase was not large. Except for those specimens containing slag, 1-day strengths higher than 3000 psi are obtainable with a water-to-cementitious-material ratio (w/c) of 0.40 with all of the concretes tested with Type III cement as well as control concretes with Type II cement. Concretes with slag and silica fume reached compressive strengths of 3000 psi in a little more than 2 days.

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