Tensile behaviour of basalt textile-reinforced mortar (TRM) composites at intermediate strain rates for structural strengthening

Textile-reinforced mortar (TRM) composites have become a preferred solution for strengthening masonry and concrete structures owing to their durability, ease of application, and compatibility. The quasi-static tensile response of TRMs is well established; however, their performance under dynamic loading remains poorly understood. This study investigates the tensile behaviour of BTRM composites at strain rates ranging from 10⁻⁵ to 9/s, using high-speed servo-hydraulic and Zwick testing systems and the digital image correlation (DIC) technique. Two specimen preparation methods were explored: moulded (M) and cut (C). The BTRM composites demonstrated strain-hardening behaviour, displaying bi-linear or tri-linear stress-strain responses depending on the strain rate and specimen type. C specimens maintained relatively consistent mechanical properties across the strain rates, while M specimens experienced enhanced first cracking stress, tensile strength, strain capacity, and toughness beyond 5/s. The post-cracking stiffness and efficiency of the reinforcing grid were reduced with increasing strain rate, with efficiency factors dropping from >0.9 in quasi-static tests to as low as 0.5 under dynamic loading. The common failure mechanisms were multiple cracking, grid rupture and telescopic failures. Extensive grid pullout and delamination failures were observed only under dynamic loading conditions. Compared to glass and carbon TRM composites, BTRMs at dynamic strain rates showed similar stress-strain relationships but lower strength and strain capacity. The results reveal the potential and constraints of BTRMs in dynamic structural applications, pointing to the need for stronger grid-to-mortar interactions to improve performance at dynamic strain rates.