Fabric-reinforced cementitious matrix (FRCM) systems are increasingly considered for the strengthening of masonry members, especially in conservation-oriented applications where compatibility with the substrate and reduced invasiveness are essential. In the confinement of masonry columns, however, the effectiveness of these systems cannot be attributed only to the tensile capacity of the textile, since stress transfer, matrix cracking, fibre mobilisation and the mechanical response of the masonry substrate all contribute to the global behaviour. This study investigated the axial response of clay brick masonry columns confined with polyparaphenylene benzobisoxazole (PBO)-FRCM systems, with particular attention to the combined influence of fibre density and matrix type. The experimental programme included the mechanical characterisation of the constituent materials, direct tensile tests on FRCM coupons and axial compression tests on fourteen masonry columns. Three matrices were considered, namely lime-based, cement-based and alkali-activated mortars, together with two PBO mesh architectures having fibre densities in the main direction of 22 g/m² and 70 g/m². The tests were organised in two series characterised by different reference masonry strengths, thereby allowing the role of the substrate to be considered in the interpretation of confinement effectiveness. The results showed that the denser PBO mesh led to higher confined compressive strength, although the improvement was not proportional to the increase in fibre density and was not accompanied by a comparable increase in post-peak deformation capacity. The comparison between coupon and column tests indicated that the post-cracking response of the FRCM jacket played a key role in the activation of confinement. The alkali-activated matrix provided a significant strengthening effect, although its response was affected by shrinkage-induced cracking and reduced fibre mobilisation. Finally, the analytical comparison highlighted the need for predictive models able to account for fibre density, matrix behaviour and substrate strength.
The effectiveness of sustainable and conventional PBO-FRCM systems for masonry column confinement: Influence of mortar type and fibre density
Mauro M.;Mazzuca P.
;Ombres L.
2026-01-01
Abstract
Fabric-reinforced cementitious matrix (FRCM) systems are increasingly considered for the strengthening of masonry members, especially in conservation-oriented applications where compatibility with the substrate and reduced invasiveness are essential. In the confinement of masonry columns, however, the effectiveness of these systems cannot be attributed only to the tensile capacity of the textile, since stress transfer, matrix cracking, fibre mobilisation and the mechanical response of the masonry substrate all contribute to the global behaviour. This study investigated the axial response of clay brick masonry columns confined with polyparaphenylene benzobisoxazole (PBO)-FRCM systems, with particular attention to the combined influence of fibre density and matrix type. The experimental programme included the mechanical characterisation of the constituent materials, direct tensile tests on FRCM coupons and axial compression tests on fourteen masonry columns. Three matrices were considered, namely lime-based, cement-based and alkali-activated mortars, together with two PBO mesh architectures having fibre densities in the main direction of 22 g/m² and 70 g/m². The tests were organised in two series characterised by different reference masonry strengths, thereby allowing the role of the substrate to be considered in the interpretation of confinement effectiveness. The results showed that the denser PBO mesh led to higher confined compressive strength, although the improvement was not proportional to the increase in fibre density and was not accompanied by a comparable increase in post-peak deformation capacity. The comparison between coupon and column tests indicated that the post-cracking response of the FRCM jacket played a key role in the activation of confinement. The alkali-activated matrix provided a significant strengthening effect, although its response was affected by shrinkage-induced cracking and reduced fibre mobilisation. Finally, the analytical comparison highlighted the need for predictive models able to account for fibre density, matrix behaviour and substrate strength.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
