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An innovative experimental methodology has been developed to analyse the microstructural
characteristics of concrete, responsible for many peculiar features of the fracture phenomenon. By means
of a completely automatised laser system, the three-dimensional morphologies of concrete can be
digitised. Considering planar cross-sections of the virgin material, the pore and void distribution can be
easily extracted from the laser-scanned topography. This procedure, which yields the effective depth and
shape of the pores, permits to overcome the drawbacks and ambiguities of traditional image analysis
techniques, where dark particles often confuse with pores. Calculating the fractal dimension by means of
two different algorithms, allows us to confirm the lacunar fractal character of the stress-carrying section.
This important feature is at the basis of the size-effect on concrete nominal tensile strength.