Petrographic Characterization of Concretes with Replacement of Coarse Aggregates by Steel Slag
Abstract:
The replacement of aggregates in concrete formulations is a common practice for improving properties such as strength, durability, impermeability, and workability. One material used for this purpose is slag, a by-product of the steel industry. During the setting and hardening of concrete, cracks may form, which play a critical role in the penetration of corrosive agents that degrade its properties. The objective of this work was to study the Interfacial Transition Zone between the cement paste and slag aggregate, due to the significant impact of microcracking on concrete properties. The micro-structural fractographic study focused on this aggregate-paste transition zone, which is generally the weakest link and is considered the strength-limiting phase of concrete. This study provides valuable information on the material's properties, especially its defects. Polished and fractured surfaces of con- crete with different proportions of steel slag were characterized by scanning electron microscopy. All concrete samples with a replacement rate of 25% to 100% showed a dense internal structure with well-bonded paste-slag interfaces. Only isolated microcracks were observed in the cement paste, within which new hydration products are expected to form over time, potentially enhancing the concrete's long-term strength and durability. Optical micro- scopic examination of in sections confirmed the dense and compact structure of the concrete. The resulting good compressive strength demonstrated the advantages of incorporating slag.
