STRENGTH GROWTH AS CHEMO-PLASTIC HARDENING IN EARLY AGE CONCRETE

This paper is concerned with modeling, identification, and experimenta l determination of thermo-chemo-mechanical couplings in early age conc rete for the prediction of deformation and cracking on account of stre ngth growth as chemo-plastic coupling within the theory of elastoplast icity. By applying the thermodynamic framework of reactive porous medi a to concrete at early ages, the coupling terms result from Maxwell sy mmetries. They lead to account for autogeneous shrinkage; hydration he at; and strength growth due to chemomechanical, thermo-chemical, and c hemo-plastic coupling with a minimum of material parameters of clear p hysical significance and accessible by standard material tests. Furthe rmore, the diffusion of water through the layers of hydrates already f ormed is considered as the dominant mechanism governing the kinetics o f hydration. To integrate this micromechanism in the macroscopic model ing, the ''normalized affinity'' is identified as an intrinsic kinetic function that characterizes the macroscopic hydration kinetics of con cretes. Finally, by way of example, a Drucker-Prager criterion with is otropic chemical hardening is worked out that takes into account the e volution of the plastic properties (crack threshold and hardening/soft ening properties) with the hydration advancing.