Applied Modeling of Moisture Phenomena in Concrete

Abstract: This thesis contains new and improved calculation models, based on applied research merging numerical modeling and material research, in the areas of hydration and chemical binding of water, sorption of moisture and transport of moisture in concrete. The proposed model for hydration and chemical binding of water is based on general kinetics modeling and calculates degree of hydration directly, without using of equivalent time of maturity. It handles dependencies on temperature as well as availability of binder and water. It models the dormant phase in the beginning of hydration. It allows also for linear variability with temperature of how much water is bounded per amount of binder, which models cross-over effects in development of chemical binding of water, measured at different temperatures. In the area of moisture sorption a family of models is proposed, building on a domain-based approach combined with explicit modeling of sorption site concentration for various desorption and absorption conditions by a matrix of adaptable values. The proposed modeling idea offers a spline-like possibility of choosing the amount of adaptation parameters and the precision of the model. Two formulations of the sorption model are presented – for both isothermal and non-isothermal conditions. A selection of methods to adapt the parameters to measured data is proposed for various situations, also covering both isothermal and non-isothermal conditions. Their properties are to some degree mathematically shown/proved and their performance is discussed.In the area of moisture transport, a family of models is proposed, conceptually similar to the proposed sorption models. It also builds on a domain-based approach combined with explicit modeling of concentration of contributions to the overall transport, for various desorption and absorption conditions by a matrix of adaptable values. The proposed modeling idea offers a spline-like possibility of choosing the amount of adaptation parameters and the precision of the model. Three formulations of the transport model are presented – one for isothermal conditions, one generalized for non-isothermal conditions and one simplified for non-isothermal conditions where capillary suction is assumed to dominate transport phenomena. A selection of methods to adapt the parameters to measured data is proposed for various situations, covering all three proposed model versions. Their properties are to some degree mathematically shown/proved and their performance is discussed.