Seismic Retrofitting of Historical Masonry Structures by FRCM Systems Subjected to Degradation Phenomena

Fiber Reinforced Cementitious Matrix (FRCM) systems have successfully emerged as seismic retrofitting technique of masonry structures, exploiting their mechanical compatibility with the latter. However, the long-term durability of FRCM systems under degradation phenomena related to temperature variations and time of exposure to aggressive environments represents a critical concern, affecting both mortar and fibrous reinforcements. Indeed, whereas the strength degradation of FRCM composites is due to the effect of temperature on the mortar, durability to exposure to an alkaline environment depends on the contact between reinforcement fibres and the surrounding lime-based mortar representing a potential chemical threat. Aim of the present work is the evaluation of the long-term effectiveness of FRCM systems used for the seismic retrofitting of a two-storey masonry structure with mechanical properties typically found in historical masonry buildings located in Calabria (Italy). Two environmental conditions are analysed for lime-based mortar and E-glass and basalt fibres FRCM reinforcements: i.e. different temperature variation, ranging from the ambient (e.g. 23 ℃) up to a maximum (e.g. 80 ℃) value corresponding to intense solar radiation; different accelerated ageing times, varying from 7 to 180 days. To this end, calibration of the tensile strength of glass and basalt fibres is proposed on the basis of experimental tests available in the literature. Finally, nonlinear static analysis of the retrofitted masonry structure is carried out in order to evaluate the influence of different aggressive environmental exposures on the effectiveness of FRCM systems.