Chloride binding in Portland limestone cements (PLC) can be attributed to the chemical reaction between chloride ions and carboaluminate phases to form Friedel’s salt and the physical interaction between chloride ions and calcium-silicate-hydrates (C-S-H). This thesis examines the chloride binding of mortar samples containing varying amounts of limestone, fly ash, silica fume, and slag, exposed to NaCl and CaCl₂ salts mixed in simulated pore solutions at 23°C. PLC and OPC+10LS systems can be used as a direct substitute for OPC as there is no significant difference in bound chloride contents. There is variation among the amount of chlorides bound by the mixtures with different SCM contents. Fly ash, silica fume, and natural pozzolans do not affect the chloride binding capacity in the presence of limestone. Slag significantly increased the bound chloride content by up to 21% at 0.1M NaCl in a cementitious system containing up to 15% interground limestone. Based on these findings, as it relates to chloride binding, limestone should be considered part of the binder content.
Funding Statement (additional comments about funding)
The author acknowledges support from Caltrans for partial support of this work through the project “Impact of Use of Portland Limestone Cement on Concrete Performance as a Plain or Reinforced Materials” through Task 3163.