An improved model to predict the ultimate drying shrinkage of concrete

An improved model to predict the ultimate drying shrinkage of concrete is proposed. The model is derived from the theory of elasticity, composite theory, and microstructural considerations. The model includes the effects of the drying shrinkage of paste, the relative restraining volume of the aggregate and unhydrated cement, the elastic modulus, and Poisson’s ratio of the shrinkage active phase (hydration products), the shrinkage restraining phase (aggregate and unhydrated cement) and the concrete. The model requires the ultimate drying shrinkage of a paste of the same w/c ratio as the concrete. It was found that the elastic modulus of concrete can be accurately predicted by using a model intermediate between the extreme boundaries described by Paul. The improved model proposed was tested on shrinkage data for thin mortar specimens at 50% relative humidity (RH) found in the literature for a wide range of aggregate content and curing times, and the results confirm the validity of the model.