ABSTRACT
The mechanism of concrete shrinkage is mainly controlled by the relative humidity (RH) gradient in its pore-structure. The change in the RH in the long term is mainly controlled by moisture diffusivity and saturation degree, which are affected by many internal and/or external factors. In this paper, the impact of size and shape of the concrete member on the RH gradient and hence the shrinkage behaviour of the member, is explored. Generally, there are many engineering 1D models for time-dependent deformation that can predict the size/shape effect on concrete shrinkage using a parameter called the notional size (h0) defined by the ratio between the total area of the member’s cross-section to the perimeter of the surface that is in contact with the outer environment. A key contribution of this paper is re-examination of the capability of Eurocode 2 to capture shape and size effects that has so far not been accounted for. This is achieved via computationally intensive 3D numerical analysis of different shapes and sizes of concrete members. For the numerical analysis, a Hygro-Thermo-Chemical (HTC) model with elasticity is used, which essentially incorporates heat diffusion, moisture diffusion, hydration reaction and shrinkage. 3D simulations of different shapes and sizes of concrete structural members suggest that the notional size parameter in its present form may be insufficient and does not capture the shape effect, leading to a proposal of shape factors.
