Concrete confinement with a cement based high strength composite material

The performances of plain concrete elements wrapped with PBO (short of Polypara-phenylene-benzo-bisthiazole) fiber meshes embedded into an inorganic stabilized cementitious matrix (Fiber Reinforced Cementitious Mortar, FRCM) are analyzed, both theoretically and experimentally, in the paper. The aims of the paper are (i) to evaluate the effectiveness of the confinement of the concrete strengthened with the PBO-FRCM system, and, (ii) to define analytical relationships able to characterize the stress–strain response of the PBO-FRCM confined concrete. An experimental investigation, carried out on cylindrical specimens confined with the PBO-FRCM system, varying the fibers reinforcement ratio, the fibers orientation and the compressive concrete strength, is described. Results of tests are, then, utilized to compare experimental results against predictions both of some guidelines and theoretical models proposed for the analysis of confined concrete elements. Results of the comparison were presented and discussed in the paper. A simple semi-empirical model to predict axial peak strength and associated axial strain in PBO-FRCM confined concrete is also proposed.