Oa. Kayyali et Mn. Haque, THE CL- OH- RATIO IN CHLORIDE-CONTAMINATED CONCRETE - A MOST IMPORTANT CRITERION/, Magazine of Concrete Research, 47(172), 1995, pp. 235-242
Chloride-contaminated concretes were produced either by admiring sodiu
m chloride with original mixes or as a result of exposure to external
sodium chloride solutions. Free chloride and hydroxyl ion concentratio
ns in the pore solutions of the concretes were determined. It was foun
d that the value of free chloride content by itself cannot provide a m
eaningful indication of the susceptibility of the reinforcement to chl
oride-initiated corrosion. The ratio of free chloride to hydroxyl ion
concentrations in the pore solution and differentiation between admire
d and externally applied chloride are found to be factors that must be
known if indicative values to predict corrosion are sought. Charts gi
ving safe regions of Cl-/OH- values for various concretes are suggeste
d. The use of a superplasticizer in concrete making was found to incre
ase the concentration of free chloride and to raise the value of Cl-/O
H- ratio in all the concretes tested. The use of fly ash was found ben
eficial in immobilizing the chloride ions in non-superplasticized conc
rete. However, in concrete made with a superplasticizer the inclusion
of fly ash was found to cause a greater release of chloride ions into
the pore solution.