Adaption of the FIB bulletin 14 design guideline for externally bonded bending reinforcement made of a textile reinforced cement composite

Until now the most commonly used materials for externally reinforcing concrete structures are Carbon Fibre Reinforced Polymers (CFRP). Design guidelines exist for these CFRP-reinforcing materials and are described in the FIB bulletin 14. However, other cement matrix strengthening materials, such as Textile Reinforced Cement (TRC) composites are emerging, due to the increasing fibre volume fraction that can be achieved in production and the resulting relatively high mechanical capacities. Currently, no design guidelines exist for the strengthening of concrete structures with these cementitious composite materials. This paper contributes to the adaption of the FIB bulletin 14 for TRC by proposing new design parameters for the modelling of debonding failure. To achieve this, 24 single lap shear tests, with different bond lengths and TRC thicknesses are performed and thoroughly analysed. Finally, the adapted design rules are evaluated by tests on 0.6 meter span TRC reinforced beams. Due to a difference between the observed (failure in composite action) and predicted (failure by loss of composite action) failure mode, the FIB bulletin 14 underestimates the ultimate bending load. These observations indicate the need for a new design method for TRC external reinforcement that goes beyond the adaption of the parameters in the existing CFRP design.