Chloride diffusion measured by a modified permeability test in normal and blended cements

Abstract

Chloride permeability was determined using a modified version of the ASTM Standard Method. A current passing through a mortar was monitored at regular one minute intervals over a 72 h period for each sample and the ionic flux calculated. This RTC (rapid test coefficient) method was used to determine the chloride diffusion coefficient for normal and blended Portland cement mortars containing silica fume, fly ash, natural pozzolan, activated clay, and granulated blast slag, respectively. The RTC method was applied to determine chloride permeability when silica fume is incorporated into cement mixes. Also, the porosity and absorptivity of these mortars and the corrosion activity of embedded reinforced specimens were measured. A good correlation was found between the coefficient obtained by the RTC method and that determined from the increased chloride concentration, and on the other hand, a good correlation was also found between pozzolanic characteristics and this last chemical parameter and/or its direct and indirect related parameters. The proposed method can be used as a quick tool to evaluate chloride diffusion.