Monitoring chloride concentrations in hardened cement pastes using ion selective electrodes

In a previous paper (1) it has been shown that silver/silver chloride ion selective electrodes are stable in a simulated pore solution and that the potential of these electrodes is a function of chloride ion activity. This has now been compared with chloride concentrations in the pore water, found using a pressure extraction technique, with chlorides added as sodium chloride to the mix water in concentrations ranging from 0.046Mdm(-3) to 0.46Mdm(-3) to ordinary portland cement pastes with a water cement ratio of 0.45. The results show good correlation between concentration added and activity calculated from electromotive force data, with an activity coefficient of 0.46 +/- 0.07, which agrees with values calculated in the previous paper.