Separation of thermal and autogenous deformation at varying temperatures using optical fiber sensors

Common, high and ultra high performance concretes undergo autogenous deformation (AD) when hardening. Deformations are often measured in specimens cured in so-called autogenous conditions, where fully coupled thermal deformation (TD) and AD are the only deformations. Therefore, in autogenous conditions, a decoupling technique must be used to separate the contributions of TD and AD. This paper presents a new technique using optical fiber sensors in specimens that are cured at varying temperatures and in autogenous conditions. Degree of reaction indexes (DRI), sometimes called maturity and equivalent time, are employed to separate TD and AD. The paper begins with a summary of the application of DRI to decoupling techniques, with particular focus on theoretical limits and potential for deformation separation. Current practices related to decoupling and modeling of the thermal and autogenous deformation are evaluated through comparison with experiments. Results confirm that testing improves the accuracy of estimation of values for the thermal expansion coefficient (TEC). Moreover, since AD swelling is detected for all tests, models that include the assumption that AD is exclusively shrinkage are not appropriate for describing AD at varying temperatures.