Development and performance evaluation of a novel high-ductility fiber-reinforced lime-pozzolana matrix for textile reinforced mortar (TRM) masonry strengthening applications

This paper discusses the development of a high ductility fiber reinforced lime mortar with deflection hardening behavior. In this study, polypropylene fibers have been incorporated in a cementless reference matrix comprising of Natural Hydraulic Lime, silica fume, siliceous aggregates and workability aid admixtures. The properties of the reference and fiber reinforced mortar compositions were assessed by means of standardized laboratory tests and scanning electron microscopy. The reference composition gave an average compressive strength of 12 MPa, rendering it suitable for structural applications. Fiber addition at a dosage of 0.76% by wt. of solids led to a reduction of the compressive strength; however, sufficient load bearing capacity was still achieved (8 MPa). More importantly, the fibers enabled the mortar to sustain useful load after damage initiation, improving post-peak ductility under compression and allowing the material to reach bending stresses up to 20% higher than the first-crack strength. To evaluate the practical application of the proposed materials, their use as matrices in textile reinforced mortar (TRM) strengthening systems was investigated through pilot applications on stone masonry. Diagonal compression tests were performed on 9 ashlar masonry wallettes, including both un-retrofitted and TRM-retrofitted specimens. Single-sided TRMs consisting of alkali resistant glass textiles embedded in either the reference or the fiber reinforced mortar were considered. Specimens retrofitted with TRM constructed using the fiber reinforced mortar, exhibited a remarkable ~ 270% increase in shear strength and > 50% higher deformation capacity, compared to un-retrofitted ones. The strength increment achieved with the reference mortar as the TRM matrix was 80%, with minimal impact on ductility. The TRM comprising the fiber reinforced mortar also showed superior performance in terms of ability to retain integrity at high levels of shear deformation. Overall, the results indicate that the use of fiber reinforced lime matrices in TRM systems applied to masonry substrates has the potential to substantially enhance mechanical performance under in-plane loading, even in cases where only single-sided retrofitting can be realized.