A chemo-mechanical model of lime hydration in concrete structures

A size-effect theory is herein introduced to investigate the average expansion of concrete containing free lime (CaO) and impurities. By drawing an analogy with the structural size-effect, the phenomenon of CaO hydration shows a characteristic length, whose dimension remains constant at all scales. If a grain of free lime is assumed to be a sphere, only a thin layer on the external surface hydrates and doubles the volume, as confirmed by the results of 2D finite element analyses and by some experimental observations. For practical applications, a simplified chemo-mechanical model of CaO hydration is eventually proposed, to predict the consequences of uncombined lime in concrete structures.