Time-dependent changes of mechanical properties of polymer-based composite materials for adhesive anchor systems

The long-term performance of adhesive anchor systems is largely determined by the time-dependent mechanical properties. As polymer-based composite materials, the properties of adhesives change during their service life dependent on environmental factors. Therefore, the influence of aging time on Young's modulus and tensile strength of two different industrially produced materials (epoxy, vinylester) with a high filler content (20-50 vol %) were investigated considering that most literature is focused on neat resins. Mechanical properties of the vinylester based material increased with time and curing temperature. While the strength of the epoxy system increased at higher post-curing temperatures, the modulus slightly decreased, which is in contrast to most literature studies and interpreted as relaxation effect. Changes in the weight of the specimens were monitored. In contrast to other hydrolytic aging studies on submerged specimens a comparably low amount of moisture absorption of the epoxy was found when aged under realistic conditions and desorption of water of the vinylester was observed, which is an uncommon behavior. The reactivity of cement as a filler material was studied by X-ray diffraction (XRD), revealing inert cement phases even at higher temperatures and the presence of water. The results are discussed and compared to available data from literature.