Experimental study on Basalt TRM-to-concrete bond under intermediate strain rates

The bond behaviour between Textile Reinforced Mortar (TRM) composites and their substrate is a decisive factor in the efficiency of strengthening interventions. While extensive research has addressed TRM bond performance under quasi-static conditions, the response under dynamic (intermediate and high) strain rates remains largely unexplored. In particular, no studies to date have characterised the dynamic TRM-to-concrete bond behaviour, despite its fundamental role in governing load transfer and structural performance under impact or blast scenarios.

This study presents the first experimental investigation of the bond performance of Basalt TRM (BTRM) systems at intermediate strain rates on concrete substrates. Quasi-static and impact bond tests were conducted using a modified beam test setup comprising two concrete prisms connected by a hinge, with the composite installed on the underside of the beam. Dynamic loading was induced by controlled drop-weight impacts from 400, 600, and 800mm. The impact force was recorded via a high-frequency accelerometer and validated using high-speed imaging and Digital Image Correlation.

The results show that strain rate influences TRM bond performance, with improved bond performance at strain rates between 1.4 and 3.2/s and different failure modes observed at higher loading rates. This study is the first to explain how BTRM bonds behave at intermediate strain rates. It fills an important knowledge gap and helps support the creation of testing and design guidelines for TRM strengthening systems under dynamic loading.