Assessment of mechanical and durability performances of NSC to self-healing FRC structural components under combined mechanical and environemental loadings

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Large proportion of Normal Strength Concrete (NSC) structures exposed to severe environmental conditions present an early deterioration (such as concrete cracking or spalling, rebar corrosion, etc.) and do not reach their expected lifetime. This early deterioration is largely resulting from deficient materials and inadequate structural design criteria not considering impacts of combined loadings (mechanical, thermal, chemical loads) applied to structures. A first promising method to extend significantly the durability of structures are to elaborate outstanding durability concretes, such as fiber reinforced concretes (FRC) and self-healing concretes (SHC). A second method is to evaluate the mechanical and durability performances of concretes under combined loadings found in northern conditions. The objectives of the research program are: 1) to develop new generations of Self-Healing Fiber Reinforced Concretes (SHFRC), 2) to evaluate and predict the performance of NSC to SHFRC under realistic northern conditions, and 3) to develop in long-term guidelines and design criteria allowing a significant extend of structures durability. Research activities are divided in two projects involving 13 students. PROJECT A aims to improve crack healing of SHFRC by ensuring availability of water and unreacted chemical admixtures required for healing. First, porous aggregates and superabsorbent polymers will be added in SHFRC to absorb water from exposure conditions and distribute it in cracks to favor healing. Second, chemical admixtures will be packaged in particles to limit their reaction before crack formation in SHFRC. PROJECT B aims to evaluate water and chloride transport mechanisms (diffusion, absorption and permeability) in reinforced concrete under combined mechanical and thermal loadings to model accurately service life of structures. First, the impact of constant and cyclic mechanical loadings creating cracks will be investigated on transport mechanisms of NSC, FRC and SHFRC. Second, the combined effect of mechanical and thermal loadings will be studied on transport mechanisms of these concretes. Third, these data will serve to develop a numerical model reproducing crack patterns and interactions with transport mechanisms to predict durability of structures under loads. This research program addresses the critical problem of inadequate durability of exposed reinforced concrete structures by two innovative and complementary research projects. Civil engineers neglect presently the very limited healing potential of NSC. However, elaboration of high-efficiency SHFRC will procure them new materials to improve durability of structures. Civil engineers also neglect interaction of multiple loadings on structures. Consideration of cracks caused by mechanical and thermal loadings on transport mechanisms of water and chlorides will change drastically service life predictions and demonstrate that the current design approach of structures must be modified.