Behavior of damaged concrete cylinders passively confined

This study focused on the behavior of the damaged concrete cylinders passively confined by an envelope constituted by the stack of the polymers tubes bonded by a STR resin under the axial compression load until rupture. The aim is to study the influence of the thickness of the polymer tube and the degree of damage of the concrete on the confinement rate. The compressive load was applied only on the concrete and not on the tube. Three series were considered: concrete cylinders, confined undamaged concrete cylinder and confined damaged concrete cylinder. The concrete cylinder is passively confined by 1, 2 and 3 tubes respectively. All the tubes have the same thickness but different diameters, so that during the stacking of the tubes the clearance between them is rapidly absorbed by the resin to ensure good contact and adhesion between the tubes over the all the circumference of the concrete cylinder. The effect of the radial confinement is shown by the different stress-strain curves depicted for each series of concrete cylinder. Analysis of the results obtained from the various compression tests carried out on the various short concrete cylinders shows that the ultimate stresses at the peak and the corresponding deformations experience an improvement as a function of the thickness of the polymer tube, the lateral confinement pressure does not vary linearly with the thickness of the polymer tube but above all that the confinement effect is higher for the damaged concrete cylinders Comparatively to the undamaged concrete cylinder. In conclusion, passive confinement by polymer tubes is particularly recommended for damaged concrete cylinders and columns.