PSI - Issue 78

Francesco Ascione et al. / Procedia Structural Integrity 78 (2026) 1334–1341

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In the confined specimens, failure occurred through the development of vertical cracks located at various positions along the jacket (Fig. 3.b). A dominant crack was typically observed at one of the section’s corners (Fig. 3c). Except for the specimens confined with the “green” S -TR system, where slippage was noted, it was possible to inspect the interior of the cracks after testing and clearly identify tensile rupture of the fibres (Fig.3.d). Finally, the masonry enclosed within the TR jacket appeared to be severely damaged, with extensive crushing of the clay bricks observed. 4. Concluding remarks This study aimed to explore the feasibility of employing TR systems incorporating alkali-activated mortars for structural applications, specifically for the confinement of masonry columns. The results of a preliminary experimental programme were reported, including direct tensile tests on basalt- and steel-based TR systems, followed by axial compression tests on clay brick masonry columns wrapped with both traditional and sustainable TR configurations. The systems investigated included: a commercial B-TR system, a “ green ” B-TR system, a commercial steel-based S TR system, and a “ green ” S-TR system. Results demonstrated that confinement with TR systems significantly improved load-bearing capacity compared to unconfined columns. The most significant improvement in structural performance was observed in the column confined with the commercial S-TR system, which exhibited an approximately 80% increase in peak axial load compared to the unconfined reference specimen. This enhancement highlights the high mechanical compatibility and effective stress transfer between the steel cords and the commercial lime-based matrix. In this configuration, the failure mode was characterised by tensile rupture of the steel cords, indicating near- complete exploitation of the textile’s mechanical capacity . In contrast, the column confined with the “ green ” S-TR system demonstrated a markedly lower improvement, with a peak load increase of only 17% relative to the unconfined case. This limited performance is attributed to inadequate bonding between the alkali-activated matrix and the steel cords, resulting in premature slippage of the textile within the matrix and a significantly reduced exploitation ratio. This slippage behaviour was also observed during the direct tensile tests of the “ green ” S-TR composite, where inefficient textile impregnation compromised load transfer and reduced overall stiffness in the post cracking phase. With regard to the basalt-based systems, the “ green ” B-TR configuration achieved a peak load roughly 30% higher than that of the unconfined specimen. While this represents a notable improvement, it was approximately 12% lower than the load-bearing capacity observed in the column confined with the commercial B-TR system. Nonetheless, considering the sustainable nature of the alkali-activated matrix and the inherent variability of TR systems, this reduction is considered deemed acceptable. Both B-TR configurations ( “ green ” and commercial) exhibited similar failure mechanisms in tensile testing, characterised by progressive slippage of the basalt fibres followed by localised rupture (telescopic failure), indicating a partially effective bond. These outcomes underscore the critical role of matrix – textile interaction in determining the mechanical effectiveness of TR confinement systems and suggest that improvements in fibre impregnation and bond performance are essential, particularly for alkali activated formulations. Future work should investigate improved impregnation techniques, the use of alternative sustainable fibres, and the extension of testing to full-scale applications and other loading conditions. A broader understanding of long-term performance, durability, and mechanical reliability will be essential to support the wider adoption of “ green ” TR systems in sustainable structural engineering. Acknowledgements This research was funded by the European Union – Next Generation EU (STRIPES Project – PRIN PNRR 2022 – CUP H53D23008660001). References Bencardino, F., & Condello, A. (2016). Innovative solution to retrofit RC members: Inhibiting-Repairing-Strengthening (IRS). Construction and Building Materials , 117 , 171 – 181. Candamano, S., Crea, F., & Iorfida, A. (2020). Mechanical characterization of basalt fabric-reinforced alkali-activated matrix composite: A preliminary investigation. Applied Sciences (Switzerland) , 10 (8).