Digital fracture surfaces and their roughness analysis: Applications to cement-based materials

Roughness numbers employed in morphological analyses characterize height irregularities of solid surfaces, which are also utilized in fractographic studies. In principle, roughness numbers are computed as height differences between the measured height profile and the reference level that has to be implemented into the profile. Positioning reference level is not an unambiguous computational operation and the result depends on the type of optimization procedure as well as the functional pattern used. A wrong position or an inconvenient pattern results in wrong roughness numbers, which devalue morphological analyses. The Fourier series has proved to be a reliable functional pattern capable of optimum positioning within the digitalized height profiles. The whole procedure is illustrated with fracture surfaces of hydrated cement pastes, whose fracture surfaces have been a subject of fractography analyses and morphological studies for several past decades.