Influence of curing, post-curing and testing temperatures on mechanical properties of a structural adhesive

Structural cold-curing adhesives are widely used to strengthen Reinforced Concrete (RC) structures with Fibre Reinforced Polymers (FRPs). The performance of these adhesives, and therefore the performance of the strengthening system, may be affected by temperature, as ambient-cured structural adhesives usually have low glass transition temperature (Tg). This paper presents a comprehensive experimental investigation on the influence of temperature on mechanical properties and Tg of a structural epoxy adhesive. The experimental program was divided in four groups of specimens. In Group 1, the effect of curing and post-curing temperature on Tg of the epoxy adhesive was investigated. In Groups 2–4, the effects of testing temperature, curing temperature and post-curing temperature, respectively, on adhesive mechanical properties were studied. Experimental results confirm that curing and post-curing temperature affected Tg differently depending whether the applied temperature was below or beyond the epoxy Tg. Similar behavior was observed in the mechanical properties of the epoxy, as they showed improvements when curing process (curing and post-curing) temperature was below Tg and they were negatively affected when curing process temperature was beyond Tg. Besides, tensile and compressive mechanical properties were negatively affected by testing temperatures beyond 20 °C.