Basalt textile–reinforced hybrid alkali-activated mortars: Tensile and substrate-dependent bond behaviour for masonry strengthening

ABSTRACT Textile-reinforced (TR) inorganic systems are increasingly used for the strengthening of masonry structures due to their high strength-to-weight ratio, ease of application and compatibility with historic substrates. However, most available matrices are cement- or lime-based, raising sustainability concerns, while experimental evidence on alkali-activated alternatives remains fragmented. This study investigates TR systems incorporating a coated basalt textile embedded in a slag-rich, hybrid-activated alkali-activated mortar (TRAAM), a formulation not previously investigated for TR applications, and benchmarks their performance against an equivalent lime-based system (TRLM) under identical testing conditions. The experimental programme included mechanical characterisation of the constituent materials, direct tensile tests on TR coupons, and single-lap direct shear tests on TRAAM/TRLM-to-masonry joints using Neapolitan Yellow Tuff and clay brick substrates. The experimental data were used to assess the applicability of the Aveston–Cooper–Kelly (ACK) model to the tensile response of TRAAM composites and to calibrate a local bond stress–slip law for finite-element (FE) simulations. The results showed that the basalt TRAAM system developed tensile capacities comparable to those of the lime-based reference, with failure governed by textile slippage within the matrix despite the distinct binder chemistry. The tensile response was accurately reproduced by the ACK model once an interface-efficiency factor was introduced. In terms of bond behaviour, TR systems applied on tuff exhibited similar bond capacities for both matrices, indicating favourable compatibility with this porous substrate, whereas reduced performance was observed on clay brick due to premature debonding. A satisfactory agreement between experimental and simulated axial stress–slip curves was achieved, supporting the proposed analytical formulation.