Testing methodologies for self-sensing TRM systems

It is estimated that 65% of heritage structures is structurally deficient1 and in critical need of structural and/or seismic retrofitting due to the effects of ageing, climate change and wars. Textile-Reinforced Mortars (TRM), which are externally bonded composite systems comprising inorganic matrices reinforced with advanced fibre meshes, are already regarded as an effective strengthening solution for heritage structures. They offer high strength and ductility whilst ensuring minimal invasiveness and excellent compatibility with historic substrates2. However, the low resistance to cracking of the mortar under service conditions has the potential to affect long-term performance, potentially resulting in additional repairs and costs, as well as critical safety issues. With the aim to integrate structural health monitoring technologies to ensure timely intervention, while drawing inspiration from recent advances in self-sensing materials, TRM are ideal candidates to be transformed into multi-functional systems, as both textile and mortar can be used as sensory elements through appropriate functionalisation. Despite the tremendous potential, literature is still in its infancy and solutions are limited to the use of carbon or hybrid glass/carbon textiles, where carbon yarns act as sensory element, providing nonetheless encouraging evidence that changes in the electrical impedance can be well correlated to the TRM structural state.