Development of Expansive Agent Model in a Multi-scale Thermodynamic Framework Based on Hydration and Microstructure Formation

This study aims to develop an analytical tool to predict the expansion of Hauyne and free-lime based expansive additives in RC structures. Hydration of species was based on the multi-component heat of hydration model which incorporates referential heat rate at a certain temperature and thermal activities following Arrhenius' law of chemical reaction. All other time-dependent properties of concrete such as elastic modulus, temperature, pore pressure, creep, moisture status, total porosity of interlayer, gel and capillary pores are computed internally based on the micromodels of materials inside the system. Coupling this material information with poromechanics, volumetric change generated by cement hydration and shrinkage is systematically included in the modelling of concrete mechanics, which deals with macroscopic structural responses based on the space-averaged constitutive laws on the fixed four-way cracked concrete model. Finally, the models are then verified with experimental results that could prove the models’ capability in predicting the amount of expansion under various replacement ratios.