Cracks are almost inevitable in a heterogeneous material such as concrete. However their pres- ence weakens the porous matrix resistance and constitutes a preferential flow path for fluid, gas and pollut- ants: material durability is therefore seriously affected. This paper…
Cracks are almost inevitable in a heterogeneous material such as concrete. However their pres- ence weakens the porous matrix resistance and constitutes a preferential flow path for fluid, gas and pollut- ants: material durability is therefore seriously affected. This paper deals with the feasibility of transfer proper- ties measurement tests during the post-peak cracking phase of concrete. A proper description of the evolution of these properties should be monitored in real-time as cracks open in the specimen. In this work, attention is focused on the mechanical test and the geometrical characterization of the cracks by means of a displacement measurement system together with a digital image correlation technique. The mechanical test is then en- hanced in order to establish a real-time relation between the evolution of the electrical resistance and the crack width opening in a saturated concrete sample. The experimental results show that the electrical resis- tance is constant before the peak (when no crack is observed) and decreases only when the peak of load is reached and when a crack is initiated. No threshold value and no phase shift between the crack opening and the resistance evolution have been observed, even in the case of a breathing crack. The evolution of the con- ductance has then been modeled by taking into account the (simplified) morphology of the crack and assum- ing a constant value for the electrolyte conductivity. The model and the experimental conductance through a traversing crack have proved to be in good agreement.