Experimental Investigations of the Effect of Selected Admixtures on the Resistance of Concrete to Sulfuric Acid Attack

Abstract

Each year billions of dollars are spent around the world on the rehabilitation and/or replacement of concrete sewer pipes damaged by sulfuric acid corrosion. This paper reports the findings of an extensive experimental program undertaken to evaluate the resistance of 17 different concrete mix designs with different additives and w/c ratios to sulfuric acid attack. Silica fume, Metakaolin and Organic Corrosion Inhibitors (OCI) in different concentrations were added to the cement to improve the resistance of the concrete paste to sulfuric acid attack. The weight loss of the concrete samples immersed in two concentrations of sulfuric acid (3% and 7%) was measured to evaluate the degree of concrete degradation. The effect of the various admixtures on the compressive strength and porosity of the concrete samples were also evaluated in an effort to determine the relationships between these attributes and the resistance of the concrete samples to a sulfuric acid attack. Data from a two months exposure test showed that the addition of Metakaolin or OCI to the concrete mix resulted in a significant improvement in the concrete resistance to sulfuric acid attack compared to the control mix. Silica fume treated concrete exhibited little or no improvement compared to the control mix. The data also showed that the compressive strength and porosity of the concrete provide little guidance if any to the resistance of the concrete paste to sulfuric acids attack.