Temperature-Affected Behaviour of Basalt and Aramid-Glass Fibres FRCM Systems

In recent years, an increasing number of masonry and reinforced concrete structures have been externally retrofitted with a wide variety of composite materials such as FRCMs (Fibre Reinforced Cementitious Matrices). The positive effects provided by these strengthening interventions on the global and local structural behaviour have already been demonstrated and confirmed by numerous authors and experimental studies. However, the effects of detrimental environmental actions, such as temperature variations, on the durability of these materials are still an open frontier. In this experimental campaign, two lime-based FRCM systems, composed of basalt or aramid-glass fibres, were exposed to different temperature levels, ranging from 40 ℃ up to 140 ℃. Tests were carried out on thermally conditioned dry textiles and FRCM coupons. In addition, single-lap direct shear tests were performed on conditioned FRCM-strengthened masonry wallets. In all cases, tests were carried out with the specimens still inside the thermal chamber used to impose the environmental condition. K-type thermocouples embedded inside the FRCM reinforcements helped define the exposure times and the final conditioning protocol to be used for all the tests. The experimental outcomes displayed a significant impact on the tensile capacity of the bare textiles and FRCM coupons, with similar trends shared between the two systems. Conversely, results from the single-lap direct shear tests confirmed that the temperature was capable of altering the maximum bond force and failure mode in the basalt system, while affecting the bond capacity of the aramid-glass system without inducing a clear shift in the failure mode.