Title: Numerical Simulation of Internal Relative Humidity of Concrete Exposed to Drying
Author(s): Sarah De Carufel, Andrew Fahim, Pouria Ghods, and Rouhollah Aalizadeh
Publication: Materials Journal
Appears on pages(s): 101-110
Keywords: ASTM F2170; concrete drying; concrete relative humidity; finite element modeling; moisture transport; permeability; pore size distribution; resilient flooring
This paper presents a model developed to predict the internal relative humidity (RH) of concrete during drying. The model makes use of simplified inputs, including the concrete mixture design and the cement Bogue composition, thus making it accessible to engineers and practitioners. These inputs are used to separately determine the permeability of both liquid and vapor phases, hence solving for moisture transport through an empirical derivation of the (de) sorption isotherm, total porosity, and pore tortuosity. The model is validated using previously published literature data as well as experiments designed specifically for model validation. The model was found successful in predicting RH profiles for the validation data with the simple inputs required. However, it was found that in cases where the standardized ASTM F2170 method is used to measure RH, the agreement between the model and experimental data decreases. This was found to be related to errors associated with performing humidity measurements within cavities drilled in concrete. Such errors are discussed, and room for improvement in in-place humidity measurements is proposed. Finally, the model is used to validate the use of RH measurements at a specific concrete depth to evaluate the susceptibility of moisture-sensitive flooring to failures.