Acceptance Criteria for Tensile Characterization of Fabric-Reinforced Cementitious Matrix Systems for Concrete and Masonry Repair

Abstract

Fabric-reinforced cementitious matrix (FRCM) composites are a new class of materials used to repair and strengthen existing structures. Mechanical performance varies widely based on the type and volume of fibers, fabric architecture, mortar properties, and bond characteristics. Moreover, test setup and boundary conditions are of the utmost importance for their mechanical characterization because of the complex interaction between fabric and brittle matrix. Therefore, the challenge is to define characterization and acceptance criteria that are (1) suitable for a wide spectrum of existing FRCM systems, and (2) produce representative values for the design of strengthened members. In this paper, three FRCM systems comprising carbon, glass, and steel fabrics were tested in accordance with two different acceptance methods. One method, which has been developed and adopted in the United States, is based on tensile tests on FRCM coupons with a clevis-grip mechanism that allows slippage at the fabric–matrix interface and provides mechanical properties that are directly used for design. The other method, developed within RILEM TC 25-CSM, combines the results of clamping-grip tensile tests on bare textile specimens with those of FRCM-to-substrate shear bond tests to obtain mechanical properties accounting for a broad range of possible failure modes. The results provided by the two methods are discussed and compared in relation to FRCM field applications.