Strain-Hardening Cementitious Composite (SHCC) For Durable Concrete Repair

Infrastructure is ageing and we are facing a serious challenge on how to deal with it. One possible solution is to repair it, but the life of current concrete repairs, including all types of repairs and application of different materials, is not satisfactory and there is an urgent need for improvement. Understanding the damage development in a repair system, and how to predict, model and prevent its failure is critical to improving performance of concrete repairs. Therefore, the aim of this work was to experimentally and numerically study the interaction between the repair material and existing concrete in two aspects which are so far scarcely understood. Firstly, the dynamics of moisture exchange in repair systems was studied, because this interaction is critical for the development of properties of the repair material and the interface. Secondly, the interaction between the repair material and the substrate, i.e. fracture behaviour of the repair system under different exposure and loading conditions was investigated. The main repair material used in this study is a recently developed fibre reinforced ultra-ductile cement-based material, known as SHCC (Strain Hardening Cementitious Composite). Fine PVA fibres and special material composition ensure that instead of single crack localization, like with conventional concrete, many tiny cracks are generated in SHCC. This is better for durability of repairs and enhances ductility and damage resistant behaviour. Finally, based on acquired knowledge, SHCC and four other repair materials were applied and inspected in a trial repair of the 70-year-old Maastunnel. More details about the presented work can be found in [1].