The relative tendency of different portland cements to remove chloride ions from the mix water by forming chloro-complexes is an important factor in the study of the corrosion of the embedded steel. The tri-calcium aluminate (C 3 A) phase of the ordinary portland cement (OPC) plays a dominant role in binding the chloride ions, but little quantitative information is available in the literature concerning the relative influence of the tetra-calcium aluminoferrite (C 4 AF) phase of the cement. The present investigation is an attempt to elucidate the role of C 4 AF in the sulphate resistant portland cement with respect to chloride binding. It is concluded that the chlorides in SRPC are bound in the form of the chloro-complex C 3 F.CaCl 2 .10H 2 O which is derived from the C 4 AF phase of the cement.