Investigation on the Relationship between Microstructure and Fracture Properties of Self-Compacting Concrete (SCC)

Self-compacting concrete (SCC) is a high-performance concrete that is increasingly replacing conventional concrete because of its many advantages. SCC is prepared with chemical and mineral admixtures to achieve increased flowability. These admixtures modify the microstructural characteristics of SCC, which in turn affect the mechanical and fracture properties of concrete. In this study, an attempt has been made to establish the relationship between the microstructure and fracture properties of SCC mixes. The fracture properties are studied by using the RILEM work of fracture method, Bazant’s size effect, and the Wittman boundary effect models. Microstructural characterization has been carried out using X-ray diffraction, scanning electron microscopy (SEM), and microindentation techniques. It is revealed that the presence of mineral admixtures alter the microstructural skeleton of SCC, which in turn increase its brittleness. However, it is also found that the reason for brittleness is not because of cracking through aggregates as is reported in many literature regarding high-strength concrete; on the contrary, the cracks are passing through the interfacial transition zone or matrix in all SCC mixes, as is revealed by SEM images. Furthermore, it is found that the mechanical properties of the aggregate used have a significant influence on the fracture properties of the mixes.