Drying creep of concrete: constitutive model and new experiments separating its mechanisms

A new experimental method which allows the direct separation of the components of drying creep due to microcracking and stress-induced shrinkage is developed, demonstrated and validated. The basic idea is to compare the curvature creep of beams subjected to the same bending moment but very different axial forces. The results confirm that drying creep has two different sources: microcracking and stress-induced shrinkage. The latter increases continuously, whereas the former first increases and then decreases. The test results are fitted using a finite element model. The results validate the present model for drying creep. The microcracking is described by an established model, and the free (unrestrained) shrinkage of a material element is shown to depend approximately linearly on the humidity drop.