This paper analyses the influence of the presence of polypropylene fibres in the microstructure of a high-strength self-compacting concrete by X-ray computed tomography and its consequences on the mechanical and fracture properties. The addition of PP fibres alters the pore structure of the concrete matrix, and this affects the macroscopic response (i.e., mechanical and fracture behaviour). A microstructural analysis of an unreinforced concrete, used as reference mix, and two polypropylene fibre-reinforced mixes with two fibre length (6 and 24 mm) were experimentally carried out. Complementary, a comprehensive experimental study of the mechanical and fracture properties of each concrete were performed. Finally, it was established a correlation between the microscopic response (pore morphology and pore distribution) and the macroscopic behaviour of high-strength self-compacting concrete.
