The role of mortar joints in FRP debonding from masonry

The present paper aims at investigating the influence of the mortar joints on the FRP-masonry debonding process and providing some insights on the reliability of experimental tests carried out on single bricks and theoretical formulas available to predict the debonding force. Masonry panels were constructed using two types of bricks and two types of mortars with significantly different properties. The masonry specimens were strengthened using glass fiber reinforced polymers and the debonding force was evaluated by a single-lap push-pull set-up. The obtained debonding forces were compared to those obtained by applying the same reinforcements to single bricks and calculated by applying theoretical formulas. The results of the study point out that neglecting the presence of the mortar joints and taking into account only brick mechanical properties, thus neglecting their surface and microstructural properties, may lead to significant inaccuracies in the estimation of the debonding force.