Corrosion Testing of Grout for Posttensioning Ducts and Stay Cables

Grout mixes using commercially available antibleed admixtures were tested for fresh properties and subsequently corrosion tested using anodic polarization to accelerate the corrosion process. Commercial admixtures that are intended to improve the corrosion protection provided by the grout were also tested in grout mixes containing the antibleed admixture. From a comparison, it was found that the antibleed admixture reduced the corrosion protection of the grout and a mix with no antibleed admixture did not. It was also found that one corrosion protection admixture improved protection while the other admixture reduced protection provided by the grout. Because the accelerated tests were conducted at an artificially high potential of 600 mV, there is some concern that the polarization level at the strand will differ significantly among grouts with varying ohmic resistances. Potentiodynamic tests were conducted on selected specimens, to investigate this effect, and were inconclusive. Further study into this effect is recommended before the higher polarization levels are used to evaluate grouts that having varying ohmic resistances.