Alkaline leaching method for the determination of the chloride content in the aqueous phase of hardened cementitious materials

Abstract

The need of determining “free” chloride content in the aqueous phase of hardened cementitious materials arises from the fact that chloride is the responsible agent of the depassivation of the rebars in reinforced concrete. This paper presents a method of obtaining free chlorides by leaching in an alkaline solution during 24 h. The method is calibrated by comparison with the values obtained by means of the pore-pressing technique (PPT). The agreement found is reasonably good in spite of the risk of excessive leaching that aims to solve part of bound chlorides. The use of decarbonated water as extraction agent has resulted appropriately, perhaps due to the fact that the samples are not powdered, instead, pieces of around 2 mm in size are used.