A detailed study of crack propagation in cement-based fibre composite beams under bending

Multiple cracking of beams made of cement-based composite was extensively studied by means of a suitable non-contact measurement technique. Images of a grid-pattern bonded onto the surface of a tested specimen were captured by a digital camera. Image processing by means of an appropriate software provided the displacement field within the zone under investigation. Cracks were revealed by discontinuities in the displacement field. Results are presented for three specimens tested in three- or four-point bending. Location, actual length and width are easily and precisely determined for each of the cracks within the zone under investigation. High sensitivity, early crack detection and no need to anticipate crack location are among the main features of this full-field measurement method. Crack propagation is derived from crack diagrams obtained at successive loading levels. Initial length, spacing, opening, propagation and profile of cracks are discussed in terms of mode of loading and bond properties of the material.