Dynamic characterisation of Basalt Textile Reinforced Mortar (BTRM) composites and BTRM-strengthened RC shear-deficient beams

While PBO and carbon offer higher tensile properties, they are expensive, have energy-intensive production, and limited recyclability. Glass fibres are economical; however, they provide lower strength and stiffness. In the case of steel grids, they are stronger than basalt fibre grids but introduce added weight and corrosion risks.

Basalt fibres, which are produced directly from volcanic rock, achieve a favourable balance of tensile capacity (1450–3200 MPa) and stiffness (~90 GPa), with high thermal resistance (up to 650 °C) and excellent chemical stability. Their low embodied energy and full recyclability align with sustainable construction practices.<br><br>Nonetheless, the mechanical behaviour of BTRMs under dynamic loading conditions remains poorly understood.

This study provides the first systematic investigation of a commercial BTRM strengthening system subjected to quasi-static and intermediate dynamic strain rates (10⁻⁵ to 10³/s). It characterises the tensile behaviour of the basalt grid and composite, evaluates the BTRM-to-concrete bond performance under impact, and assesses the retrofitting effectiveness on defective, shear-critical RC beams. Using high-rate servohydraulic testing, drop weight impact testing, and advanced Digital Image Correlation techniques, the research quantifies strain-rate sensitivity, reveals failure mechanisms, and establishes dynamic increase factors across material and structural scales.

Findings show that dynamic strain rates enhanced the tensile performance of the grid and the tensile and bond properties of the BTRM composite.<br><br>Under impact loading, retrofitted beams exhibited significant enhancements in shear capacity and impact resilience, shifting failure modes from brittle to ductile. However, dynamic loading diminished the interfacial bond between the grid and mortar components of the BTRM system.<br><br>This research challenges the adequacy of quasi-static-based design codes and contributes new methodologies for dynamic characterisation.

It supports the development of more realistic testing protocols and predictive models, informing more resilient retrofitting strategies. The outcomes of this study directly align with global sustainability goals, reinforcing BTRMs as viable solutions for prolonging the life of structures in a resource-efficient and climate-conscious manner.<br><br><i>Thesis is embargoed until 31 December 2029.</i>