The coloration phenomenon associated with slag blended cements

Blue-green coloration observed in concrete made with slag-blended cement so metimes raises concern mainly due to lack of understanding of the causes. T his article presents the results of a study conducted to investigate the va rious 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% an d 70% slag in the binder. Three different curing regimes were studied, name ly, (1) bath curing under constant temperature, (2) sealing with plastic ba gs to stop any moisture movements under constant temperature and (3) curing in water baths temperature matched to in situ conditions. Extent and inten sity of the coloration was also studied in four large-size columns by takin g 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. (C) 2001 Elsevier S cience Ltd. All rights reserved.