Performance of Slag Cement in Hydraulic Cement Concrete

The Virginia Department of Transportation began to allow the use of slag cement in hydraulic cement concretes in 1985; its use has steadily increased since then. Several years ago a study was conducted to investigate the performance of bridge decks constructed with hydraulic cement concretes containing straight portland cement and portland cement plus slag cement with a specified water–cementitious materials ratio of 0.45. At the time of the field work, these decks were 12 to 16 years old. In addition to general observations of deck condition, cores were extracted from the decks for petrographic examination of internal condition and determination of concrete transport properties by using electrical conductivity and rate of water absorption. Overall, the slag cement concretes performed well with a tendency toward lower transport properties and showed no inherent tendency for scaling. Some evidence of alkali–aggregate reactivity was observed with evident damage in one case, although it was not clear whether an insufficient amount of slag cement was used or slag cement would simply be ineffective in this case. Overall, the performance and experience with slag cement were favorable.