This study evaluates the use of five commercially available epoxy adhesives (EAs), from low to high cost, as a connection alternative of timber-concrete composites (TCCs) using cross-laminated timber (CLT) and medium-strength precast concrete (25MPa). Five alternative EAs were initially evaluated via pull-off tests to determine the adhesive strength of the interface CLT/concrete, with average results varying from 0.6MPa to 3.6MPa. Subsequently, optical and scanning electron microscopy analyses were implemented to assess the microstructure of post-tested TCC specimens, finding that usually the CLT/concrete interface was not fully glued by the EAs and that there was a positive correlation between the penetration of each EA with the corresponding tension strength of the TCCs. Then, the three EAs with the largest adhesive strengths were further tested by small double-shear (SDS) tests evaluating their shear strength and deformation, as well as damage evolution and failure modes, which were obtained using digital image correlation. The SDS test average results ranged from 2.4MPa to 8.8MPa, and the EA with the best behavior was not the one with the highest tensile strength, but rather with the highest EA penetration into concrete, demonstrating that this property highly positively impacted the shear strength of TCCs. Finally, cost/benefit analyses were obtained, and interestingly, the EA with the best adhesive/shear performance was not the most expensive alternative, opening the discussion that, even though mostly expensive EAs have been used in TCCs, the option of technically valid and low-cost EA is feasible.
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