Concrete is one of the most used building materials. It behaves well in compression. but it cracks when subjected to tensile stresses. These cracks may consequently compromise the durability of the whole structural element, i.e. acting as preferential paths for…
Concrete is one of the most used building materials. It behaves well in compression. but it cracks when subjected to tensile stresses. These cracks may consequently compromise the durability of the whole structural element, i.e. acting as preferential paths for water percolation inside the structure, leading to further problems, such as, corrosion of the steel reinforcement bars. Shape memory polymers (SMP) have been used in the past in the design of a novel system aiming to reduce the size (or possibly close) these cracks. Polyethylene terephthalate (PET) was the SMP which showed the best potential for this aim. During production, it is subjected to a drawing process at high temperature, aligning the previously random long chain molecules. The aligned molecular configuration is then frozen upon cooling but can be released by reheating above a transition temperature. PET tendons were embedded within the structural element. Being restrained, the PET tendons developed a compressive stress when activated, thereby promoting crack-closure. The tendons made of PET showed very promising results. However, the stress developed by the restrained tendons remained quite low. In this work a preliminary study of a novel hybrid tendon is presented. The tendons are made by combining the natural behaviour of the PET with a pre-stressed inner core. The new system has the potential to increase the stress developed by the tendons, hence further improving the crack-closure, and to provide reliable post-activation reinforcement.