Modelling of chloride binding related to hydration products in slag-blended cements

• The composition of the slag is crucial to the chloride binding capacity of a paste.
• The interaction between the slag and OPC components is taken into account.
• The C–S–A–H phase binds approximately two thirds of the total bound chlorides.
• The remaining third is attributed to AFm phases.
• The results of the model are highly improved from a previous model from literature.

An improved hydration model of slag-blended cements, taking into account new insights, is used to estimate and quantify the hydration products of slag-blended cements. Individual chloride binding isotherms are used to correlate these amounts of hydration products with the amount of bound chlorides. A number of parameters are directly or indirectly taken into account when estimating the chloride binding ability of a slag-blended cement paste: cement composition, slag content, water/binder ratio, curing age, and free chloride concentration. The model allows the study of the breakdown of bound chlorides by hydration products and their source – either the OPC or the slag.