Moisture and ion mobilization and stratification in post-tensioned (PT) grout during hydration

Mobilization and stratification of ions and moisture in post-tensioned tendons during grout hydration can create adverse conditions which can promote corrosion. The transport of sulfate and chloride ions associated with grout segregation in large-scale tendon mockups was assessed. The grout was mixed with 15 % excess water over the manufacturers recommended limit to promote segregation and with different sulfate and chloride concentrations. The moisture content and both sulfate and chloride ion concentrations in the grout from the top sections of the tendons were significantly higher than grout from lower elevations. An ion-concentration factor (ICF) was defined as the ratio of the ion concentration in the leachate produced from the hydrated grout and the initial concentration in the grout mix water. The ion mobility in relation to moisture was analyzed in terms of the sulfate and chloride ions and their interactions with the solid and liquid phases during grout hydration