Effect of Volcanic Pumice on the Corrosion Resistance and Chloride Diffusivity of Blended Cement Mortars

Abstract

This paper reports the results of investigation on the chloride diffusivity and corrosion resistance of volcanic pumice(VP) blended cement mortars with varying curing age of up to one year. The mortars had 0, 15% and 30% VP as cement replacement and water/binder ratio of 0.55. Tests were conducted to determine the chloride ion migration coefficient(Di) of the mortars. In addition, electrical resistivity, mercury intrusion porosimetry, and differential scanning calorimetry (DSC) tests were conducted. Electrochemical measurement was used to monitor the corrosive behaviour of the embedded steel bars. It was found that blending cement with VP significantly reduced the long-term Di and hence increased the long-term corrosion resistance of mortars. This fact was also supported by the presence of lower quantity of Ca(OH)2 and higher quantity of Friedel's salt in the VP blended mortars as observed from the DSC tests. Mortars with 30% VP showed better performance in terms of chloride ion diffusivity, chloride ingress and passivation period of embedded steel compared to control mortar with 0% VP.