Multilevel analysis of FRCM systems under controlled thermal exposures

The durability of Fibre Reinforced Cementitious Matrix (FRCM) systems under varying environmental conditions is a topic of active research, despite their widespread use in structural retrofitting and strengthening. This study investigates how temperature variations influence the mechanical properties of two distinct FRCM systems, employing glass or basalt fibres as reinforcement and the same lime-based mortar matrix. Tests were first conducted on dry fibre textiles, FRCM coupons, and single-lap direct shear specimens inside a thermal chamber for different target temperatures. Then, additional single-lap direct shear tests were performed at ambient temperature after 20 temperature cycles to investigate the residual capacity of the FRCM systems. Specific thermal procedures were adopted to manage both specimen conditioning and testing phases, ensuring consistent results. The results of tests performed inside the thermal chamber demonstrated that temperature variations can significantly reduce the tensile strength of the composites and ultimately alter the failure mode observed during bond tests at the highest investigated temperature level. By investigating the residual capacity after 20 temperature cycles, instead, it was observed that, although the thermal conditioning process did impact the composite’s bond strength, its effect was less significant compared to the tests performed inside the thermal chamber and did not modify the failure mode mechanism.