PSI - Issue 78

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

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2. Experimental investigations The experimental programme encompassed a multi-scale testing approach. Preliminary tests were carried out on the constituent materials of the TR systems, including direct tensile tests on both basalt and steel textiles, as well as compressive and flexural strength tests on the commercial and alkali-activated mortars. Composite-level performance was then assessed through uniaxial direct tensile (DT) tests on the TR systems. Finally, axial compression tests were carried out on unconfined and confined masonry columns, strengthened with four configurations: commercial and “green” versions of both basalt -based (B-TR) and steel-based (S-TR) systems. 2.1. Clay brick masonry column constituent materials Each masonry column was assembled using 16 clay bricks, which were pre- soaked in water at 20 °C for 24 hours to ensure adequate hydration prior to construction. All columns share identical geometry, featuring a square cross section of 250 × 250 mm with an overall height of 575 mm (Fig.1.a). Each brick has a height of 55 mm, and mortar joints were applied with an average thickness of approximately 20 mm. The external edges of the specimens were chamfered by light grinding, producing a rounded profile with a radius of 20 mm, in accordance with the minimum requirement specified in CNR-DT 215 (2018). The mortar, identified as type M5 in accordance with EN 1996-1-1 (1996), was composed of natural hydraulic lime (NHL), sand, and calcareous aggregates.

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Fig. 1. Clay brick masonry column: (a) geometry of the specimen (dimension in mm) and (b) experimental setup for axial compression testing.

2.2. TR Systems: Fiber, Matrix, and Composite The basalt mesh used in this study is bidirectional, consisting of basalt yarns interwoven with AISI 304 stainless steel microfilaments in a welded configuration. This textile has a surface density of 400 g/m² and an equivalent thickness of 0.064 mm. The steel reinforcement, on the other hand, consists of unidirectional ultra-high tensile strength steel (UHTSS) microcords, fixed onto a fibreglass micromesh substrate. Each microcord is composed of five wires: three arranged linearly and two helically wound. The steel mesh features a surface density of 670 g/m² and an equivalent thickness of 0.084 mm. DT tests were carried out on both types of reinforcement textiles. The basalt textile exhibited an average ultimate tensile strength of 1130.12 MPa, an average elastic modulus of 83.79 GPa, and an average ultimate strain of 0.014. The steel textile showed an average ultimate tensile strength of 2743.99 MPa, an average elastic modulus of 180.64 GPa, and an average ultimate strain of 0.020. The tensile strength values were calculated with respect to the equivalent cross-sectional area. For the basalt textile, this area was computed as 2.24 mm² by multiplying the equivalent thickness (0.064 mm) by the specimen width (35 mm). For the steel textile, the equivalent cross-sectional area was 3.22 mm², calculated by multiplying the area of a single cord (0.538 mm²) by the