TRM versus FRP: Can cement-based matrices replace organic binders in the flexural strengthening of reinforced low-grade concrete beams?

The rehabilitation of aging housing estates has become increasingly critical due to the deterioration of concrete structures from environmental exposure, design deficiencies, and poor maintenance. Fibre Reinforced Polymers (FRPs) have been extensively studied and applied for structural strengthening but exhibit limitations such as substrate incompatibility, poor performance under extreme temperatures, and moisture sensitivity—issues particularly pronounced in low-grade concrete and masonry. As an alternative, Textile Reinforced Mortar (TRM), which replaces the organic matrix in FRPs with cement-based mortar, has emerged as a promising solution. The objective of this work is to compare the structural performance of both matrices when applied in flexural strengthening of beams with the same amount of composite reinforcement (steel or carbon textiles). For that aim, twelve one-third scale beams (1.5 m span) fabricated with low quality concrete were tested under four-point bending. For the case of TRM-retrofitted beams, a custom-designed cementitious mortar was designed, characterized and used as composite matrix. The results indicate that TRM composites significantly improve load-bearing capacity and ductility, especially when steel textiles are employed, making it a feasible alternative to traditional FRP systems. The findings underscore TRM's potential as a durable, compatible, and cost-effective strengthening method, advancing its applicability in the rehabilitation of deteriorated concrete infrastructure. These results contribute to the growing body of knowledge on the application of TRM in structural rehabilitation and offer valuable insights for future research and practical applications in the field of construction.