The coloration phenomenon associated with slag blended cements

Blue-green coloration observed in concrete made with slag-blended cement sometimes raises concern mainly due to lack of understanding of the causes. This article presents the results of a study conducted to investigate the various factors that influence the coloration. Five different concrete mixes were studied with water to binder ratio ranging from 0.3 to 0.5 with 50% and 70% slag in the binder. Three different curing regimes were studied, namely, (1) bath curing under constant temperature, (2) sealing with plastic bags to stop any moisture movements under constant temperature and (3) curing in water baths temperature matched to in situ conditions. Extent and intensity of the coloration was also studied in four large-size columns by taking cores from columns at various ages. The compressive strength of the cores was also determined. The results show that the coloration is a function of rate of oxidation, curing conditions and slag content