HYDRATION PRODUCTS AT THE BLASTFURNACE SLAG AGGREGATE - CEMENT PASTE INTERFACE

Scanning electron microscopy (SEM) connected to energy dispersive X-ra y analysis (EDAX), X-ray powder diffraction (XRD) and infrared (IR) sp ectroscopy were used for identification of the hydration products in t he interface between blastfurnace slag aggregate and hydrated cement p aste. Besides the dominant portlandite crystals, the products typical for gel-like calcium silicate hydrates with CaO/SiO2 molar ratio of ab out 1.0 were identified in the interfacial zone, Evidence from SEM tog ether with the results of XRD and IR studies show some differences in the microstructure of the transitional zone compared to usual types of aggregate. The presence of Mg and S containing compounds in the blast furnace slag aggregate and their influence on the cement hydration are considered to be the main reason for such differences.