Identification of FRCM mechanical parameters for the retrofitting design of existing structures

Fabric-Reinforced Cementitious Matrix (FRCM) composites are an effective mean to retrofit damaged structures. Their action depends not only on the behavior in tension of the introduced materials, but also on the bond of the composite with the original substrate. A new Italian standard will be soon introduced, thought to allow the designer to compute the effectiveness of cement-based Externally Bonded Reinforcements (EBR) by combining simple uniaxial tensile tests with shear bond tests. An experimental investigation of FRCMs made of an Alkali-Resistant (AR) glass fabric combined with different matrices and dispersed Polyvinyl Alcohol (PVA) or high-carbon steel microfibers is presented. In this regard, relevant design parameters are matrix toughness and mortar thixotropy. Following the characterization at the material and at the interface scales, the design procedures introduced by the standard are discussed and critically evaluated with reference to an alternative basic test based on Double Edge Wedge Splitting (DEWS) principles. Preliminary conclusions concerning the reliability of the proposed approach are finally drawn.