Innovative and sustainable shrinkage-compensating concretes

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This project is part of a continuing effort at CRIB Laval (Laval University) intended to help establishing concrete repair as a legitimate engineering discipline. Ultimately, the fundamental objective is to provide the repair industry with the knowledge required to implement rational design methods and specifications for repairs. In that quest, the achievement of dimensional compatibility remains one of the most important considerations in order to consistently achieve lasting repair works that do not undergo harmful cracking. Drying shrinkage of Portland cement concrete is generally inevitable and, although its magnitude can be reduced by optimizing or modifying the composition parameters, it remains significantly larger than its ultimate tensile strain. Conversely, the use of shrinkage-compensating concrete (ShCC) may allow to achieve a zero-dimensional balance with respect to drying shrinkage, through the use of a mineral expansive agent. The experimental work carried out in recent years at Laval University to evaluate the potential of shrinkage-compensating concretes (ShCC) for use as repair materials has in fact yielded quite promising results. Nevertheless, more research is required to turn ShCC systems into a truly dependable and versatile repair option. Among the issues still unresolved, the engineering behind the shrinkage compensation process for repairs has yet to be developed. The overall influence of the type of expansive processes and their effectiveness with a variety of cement/binder systems needs to be investigated in depth. The anticipated research work will provide a basis for optimizing specifications, detailing and construction methods (repair thickness, bonding or anchoring, material selection, curing technique and duration, etc.) of ShCC repairs. Another aspect that needs to be addressed is the lack of suitable tests methods to characterize ShCC, to guide the specifications and to perform quality control. Efforts will be devoted to adapt or develop test procedures intended to better capture the particular volume change behavior of ShCC's. While the research program will be primarily dedicated to the development of more durable and sustainable shrinkage-compensating repair concretes, an objective of the research is to evaluate whether shrinkage compensation can be successfully exploited in some other specialty concretes. Ultimately, the findings are expected to benefit the overall concrete construction industry towards sustainability.