Corrosion resistance and chloride diffusivity of volcanic ash blended cement mortar

This paper reports the results of an investigation on the chloride diffusivity and corrosion resistance of volcanic ash (VA) blended cement mortars with varying curing times of up to 1 year. The mortars had 20% and 40% VA as cement replacement and water/binder ratio of 0.55. The accelerated chloride ion diffusion (ACID) test was used to calculate the chloride ion (Cl?) diffusion coefficient (Di) of the mortars using the Nernst-Plank equation for steady state condition. In addition, electrical resistivity, mercury intrusion porosimetry and differential scanning calorimetry (DSC) tests were conducted. Electrochemical measurement such as linear polarization resistance was used to monitor the corrosive behavior of the embedded steel bars. The chloride ingress into the mortars was also studied. Good correlations were found among Di, total pore volume (TPV) and electrical resistivity of the mortars. It was also found that blending cement with VA 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 VA blended mortars as observed from the DSC tests. Mortars with 40% VA showed better performance in terms of Cl? diffusivity, chloride ingress and passivation period of embedded steel compared with the control mortar with 0% VA.

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