Abstract
Hygro-thermo-chemo-mechanical modelling of time-dependent concrete behavior requires the accurate determination of a large set of parameters. In this paper, the parameters of a multiphase model are calibrated based on a comprehensive set of experiments for a particular concrete of grade C30/37. The experiments include a calorimetry test, tests for age-dependent mechanical properties, tests for determining the water desorption isotherm, shrinkage tests, and compressive creep tests. The latter two were performed on sealed and unsealed specimens with accompanying mass water content measurements. The multiphase model is based on an effective stress formulation. It features a porosity-dependent desorption isotherm, taking into account the time-dependency of the desorption properties. The multiphase model is shown to yield excellent results for the evolutions of the mechanical parameters. The evolution of the autogenous shrinkage strain and evolutions of the creep compliances for loading at concrete ages of 2 days, 7 days, and 28 days are well predicted together with the respective mass water content evolution. This also holds for the evolution of the drying shrinkage strain, at least for moderate drying up to one year. However, it will be demonstrated that for longer drying times further conceptual thoughts concerning the coupled representation of shrinkage and creep are required.
Highlights
Shrinkage and creep are important phenomena affecting the load bearing capacity, durability and serviceability of plain and reinforced concrete structures
Sciumé et al calibrated their newly introduced parameters from autogenous shrinkage tests. They justified their approach by a comparison of desorption isotherms of ordinary and high-performance concrete, which are associated with different pore structures
A similar relation is used in the present context, assuming that the change in void ratio is not caused by deformation but rather by hydration products decreasing the void volume. This assumption is in line with the approach of Sciumé et al [3], who suggested a desorption isotherm depending on the degree of hydration
Summary
Shrinkage and creep are important phenomena affecting the load bearing capacity, durability and serviceability of plain and reinforced concrete structures. Materials 2019, 12, 791 is used for predicting the interactions between substrate and hardening overlay in repair problems Another example is the multiphase simulation of the impact of drying shrinkage on the behavior of concrete structures strengthened by concrete overlays, presented in [4]. The required experiments include calorimetry tests, tests on mechanical and hygral parameters as well as sorption, shrinkage, and creep tests Since many of these properties are age-dependent, experiments have to be performed once but several times at different ages and/or for long durations. Sciumé et al calibrated their newly introduced parameters from autogenous shrinkage tests They justified their approach by a comparison of desorption isotherms of ordinary and high-performance concrete, which are associated with different pore structures.
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