Resilience of Historic Masonry After Fire: The Impact of the Stone/Mortar Nature and a Demonstration of a Novel Inspection Methodology

The impact of fire exposure on stone masonry structures is investigated in this study by testing in compression individual masonry components (bluestone and sandstone, lime- and cement-based mortars) and measuring the shear bond resistance of respective triplets. The monitoring of fracture by advanced non-destructive techniques, such as acoustic emission, ultrasound and digital image correlation, demonstrate that severe post-fire damage is evident for all materials heated above 600 °C. As a result, the damage mode shifts as micro-cracks develop at intergranular level and macroscopically, premature cracks form at the mortar-stone interface. The study proposes an integrated mechanical testing protocol and inspection methodology that can provide testing criteria and quality control analyses for a safe and durable stone masonry restoration and conservation intervention. Through a materials’ parametric analysis, for the first time in literature, the cracking morphology and strain concentrations attributed to fire exposure are linked to the chemical transformations reached on the individual masonry components.