Journal of Applied Electrochemistry, Vol.38, No.4, 445-450, 2008
Tolerance limit of chloride for steel in blended cement mortar using the cyclic polarisation technique
The tolerance limit for chloride in ordinary Portland cement (OPC) and blended cements such as Portland pozzolana cement (PPC) and Portland slag cement (PSC) was assessed by cyclic polarisation. This study covers both cement extracts and mortar. The salient features of this investigation were: in extracts, the tolerance limit for chloride actually doubles for PSC when compared to PPC and OPC. The tolerance limit for chloride for various mortars follows the order: PSC > PPC > OPC. In OPC and PPC mortar, the repassivation potential (E-rep) shifted negatively with higher amounts of free chloride but in PSC mortar E-rep shifted positively (+590 mV) even in the presence of 5,000 ppm of free chloride. PSC takes longer time (50 days) to reach E-rep indicating perfect passivity maintained for the embedded steel.