Experimental characterization of the self-healing of cracks in an ultra high performance cementitious material: Mechanical tests and acoustic emission analysis

Self-healing of cracks in an ultra high performance concrete, considered as a model material, is investigated in this paper. An experimental program is carried out in order to quantify the phenomenon, which has been mainly highlighted by means of water permeability tests until now. Mechanical behaviour of self-healed concrete under three points bending, and acoustic emission analysis of the cracking mechanisms are reported. The mechanical tests demonstrate a recovery of the global stiffness, depending on the time of healing, for specimens initially cracked and then self-healed, and a slow improvement of structural strength. The acoustic emission (AE) analysis is performed in order to show that the mechanical response is due to new crystals precipitating in the crack. The microcracking of these products during three points bending tests is highlighted and an energy analysis provides insights about the cracking process of healed concrete, including damage of the newly formed crystals and continuation of the crack propagation.