ITZ microstructure of concrete containing GGBS

The interfacial transition zone (ITZ) of aggregate-cement paste and the morphology of hydrates in concrete containing ground granulated blast-furnace slag (GGBS) have been investigated using XRD, SEM and microhardness measurements. The experimental results demonstrated that GGBS significantly decreases both the quantity and the orientating arrangement of CH crystals at the ITZ. The CH crystal size becomes smaller because of the addition of GGBS. The weak ITZ between aggregate and cement paste was strengthened as a result of the pozzolanic reaction of GGBS. The above improvements become much more significant with the decrease of particle sizes of GGBS.