A numerical microscopically informed upscale approach for analyzing the reliability of testing method for concrete resistance to freeze-thaw
Abstract
Due to the complexity of the problem, experimental studies on the frost action in concrete cannot be validated directly, since the major challenge of such a complex phenomenon is to be able to isolate the influence of each parameter involved in freezing and thawing processes. Therefore, the development of numerical tools offers an opportunity to represent the complexity of the material under study and to investigate as closely as possible the local phenomena at small scales. In this work, we adopt a micromechanical approach aiming to integrate the effect of each parameter defining laboratory exposure conditions of concrete. A multiscale approach originating from the hydration products and goes up to concrete was presented and results are compared with the experimental measurements. The results show that this numerical approach offers a satisfactory tool to predict concrete strains when exposed to freeze and thaw damage, without any calibration, by taking into account the effects of the developed pressures in pores at the microscale. An application of the model is presented to predict the strains of concrete specimens exposed to freeze and thaw cycles placed at different positions inside a climatic chamber. The temperature was recorded at different specimens’ positions inside the climatic chamber and these temperatures were applied as thermal loadings in the model. A clear correlation between the experimental degraded surfaces and the strain amplitudes recorded for each specimen is found. The study also found an inconsistency in the recorded temperature evolutions and deformation levels among the concrete specimens placed at different positions inside the climatic chamber, which calls into question the reliability of the existing normative methods in order to characterize concrete resistance to freeze and thaw.
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