Modelling creep and shrinkage of concrete by means of effective stresses

A novel model of mechanical performance of concrete at early ages and beyond, and in particular, evolution of its strength properties (aging) and deformations (shrinkage and creep strains), described in terms of effective stress is briefly presented. This model reproduces such phenomena known from experiments like drying creep or some additional strains, as compared to pure shrinkage, which appear during autogenous deformations of a maturing, sealed concrete sample. Creep is described by means of the modified microprestress-solidification theory with some modifications to take into account the effects of temperature and relative humidity on concrete aging. Shrinkage strains are modelled by using effective stresses giving a good agreement with experimental data also for low values of relative humidity. Results of four numerical examples based on the real experimental tests are solved to validate the model. They demonstrate its possibilities to analyze both autogenous deformations in maturing concrete, and creep and shrinkage phenomena, including drying creep, in concrete elements of different age, sealed or drying, exposed to external load or without any load.