Durability of adhesively bonded steel-concrete composite structures under sulfate and chloride exposure: An experimental assessment

The long-term performance of adhesively bonded steel–concrete composite structures remains a key concern for their widespread use in civil infrastructure, especially under chemically aggressive environmental conditions. This study conducts a comprehensive experimental program to assess the durability and mechanical performance of galvanised cold-formed steel profiles adhesively bonded to concrete slabs. It addresses uncertainties about the adhesive connections’ behaviour under these conditions. The research involved exposing specimens to sulfate and chloride solutions for 180 and 360 days through cyclic immersion, followed by subsequent drying conditions. To better understand all the variables of the composite specimen, all the materials were individually tested as well. Results show that sulfate exposure leads to the most severe deterioration, with a tensile strength reduction of over 50 % in the epoxy adhesive and shear strength losses of up to 60 % in composite specimens. Chloride exposure resulted in comparatively lower degradation, although it remained significant. Despite minor strength losses in steel and moderate reductions in concrete bond strength, the adhesive layer was identified as the most vulnerable component. Failures consistently occurred at the epoxy–steel interface, indicating insufficient bonding to galvanised surfaces. The findings highlight the critical influence of environmental conditions on the performance of bonded composites, underscoring the need for improved surface treatment strategies or alternative adhesive formulations for applications in aggressive environments. This research contributes with valuable insights toward the reliable implementation of adhesive bonding in structural engineering. These findings support the revision of design and maintenance strategies for adhesively bonded systems in aggressive environments.