Chloride binding in cement I. Investigations to determine the composition of porewater in hardened cement

The investigation of various methods to determine the composition of pore water in hardened cement paste showed that only by the pressing-out method correct results can be achieved. Up to the highest pressure exerted of approx. 3500 bar, the expression force hardly had any influence on the chloride and hydroxide concentration of the pore solution. Crushing of samples prior to expression should be avoided as even brief contacts of the pulverized samples with ambient air result in a decrease in hydroxide and an increase in the chloride concentration of the pore solution due to CO2 uptake.