Determination of free chloride in seawater cement paste with low water-binder ratio

Water extraction method has been widely applied to determine the free chloride content in cement-based materials. This paper studies the effects of different extraction time, curing ages and w/b ratios on the obtained free chloride content of seawater cement paste with low water-binder ratio by water extraction method. An appropriate testing process of water extraction method for pore solution acquisition and measurement of cement paste with low water-binder ratio is determined and the results are compared with that obtained by pore pressing method. The results show that the water extraction test is suitable for free chloride measurement of cement-based materials with low water-binder ratio by controlling the extraction time within a certain range about 3 min. The obtained results by water extraction with 3 min of extraction time are comparable to those obtained by pore pressing method. However, the physically bound chloride content decreases after water extraction and pore pressing tests, which indicates that the water extraction and pore pressing methods overestimates the free chloride content in cement-based materials. The effect of w/b ratio and curing age on the accuracy of this method is not evident.

Automated summary

The study investigated the effects of water extraction method on the free chloride content in sea water cement paste with low water-binder ratio, finding that an extraction time of around 3 minutes yielded optimal results. The free chloride content obtained by water extraction method was comparable to that obtained by pore pressing method, but both methods tended to overestimate the chloride content.