Chemical Features of the ITZ between Cement Paste and Aggregate

Interfacial Transition Zones (ITZ) between cement matrix and inclusions such as aggregates were studied by scanning electron microscope (SEM), electron probe X-ray micro-analyzer (EPXM) and the energy dispersive X-ray analyzer (EDXA). Particular attention was paid to the distributions of the chemical elements in the vicinity of the ITZ. The test results show that Ca, K and Fe tend to concentrate to the ITZ to different degrees. Si has relatively low concentration close to the aggregate surface, but the concentration increases with the distance away from the surface. The distributions of the chemical elements near the interface can reflect the chemical stability and the interactions of the components in the concrete, hence, it relates to the durability of concrete.