Even though reinforced concrete (RC) is one of the most used man-made materials in the world, and adequate models exist for the prediction and design of the ultimate capacity of RC structures, the prediction of service life behaviour is still not mature enough for actual design purposes, leading to inadequate service life behaviour even when regulatory prescriptions for design are strictly followed. This inadequate behaviour is mostly felt to the general public by the appearance of cracks with large width (>0.3mm), which usually end up causing severe reductions in the lifespan of RC structures, while enforcing costly repair/maintenance operations.
After an initial dormant period, the mechanical properties of concrete evolve significantly towards their final values along time. However, the process of hydration is exothermic, frequently resulting in relevant temperature variations of concrete (increases/decreases), which in turn cause volumetric deformations. Furthermore, the internal water consumption on behalf of cement hydration, together with progressive drying because of water evaporation from the concrete surface, lead to the desiccation of the pore structure, which results in contraction of the material. Any restraint to such deformations is bound to cause tensile stresses. Together with all the above phenomena, RC structures are loaded by their self-weight and external loads. The most challenging point in the prediction of service life behaviour is the adequate description of the intricate interactions that take place between self-imposed deformations (thermal and shrinkage related), viscoelasticity and the effects of applied loads in the process of crack development. These interactions are not taken into account by current regulations, and there are no integrative scientific research studies that take a systematic approach to this issue, leaving many questions unanswered.
The main purpose of this research proposal is precisely to close the research gap identified above through a comprehensive program that incorporates extensive experimental characterization, real-scale testing with monitoring of relevant data and their corresponding simulation with multi-scale and multi-physics approaches. The central innovation of this research project is the pioneering capacity of the team to integrate knowledge and research experience in both the experimental and numerical simulation fields, paving the way to an unprecedented set of integrative innovations ranging from the microstructural characterization and modelling to the real-scale testing, modelling and validation. This has never been done by a single team, and thus very solid and original outcomes are expectable. The improved predictions of cracking and service life behaviour, and resulting design recommendations, are bound to cause significant impact on new structures and processes of strengthening with cement-based materials that will have improved cracking performance and thus increased maintenance-free lifespan.