Experimental and numerical investigation of drying rate impact on moisture loss, exchange coefficient and drying shrinkage of cement paste

Assessment of moisture content evolution and drying shrinkage is important for the long-term operation of large concrete structures. This paper evaluates the impact of size and boundary conditions in predicting mass loss and drying shrinkage of cement-based materials at ambient temperature. The authors conducted the study on ordinary portland cement paste. The size of specimens spanned from 1 mm to 36 mm. The experiments were performed in environmental scanning electron microscope (ESEM), Dynamic Vapor Sorption (DVS), climatic chamber (CC) and saturated salt solutions chambers. The mass loss, as well as drying shrinkage, have been recorded and simulated. The numerical simulations of experimental results show the drying and shrinkage models' ability to consider size effects, which is essential when such models are validated on a thin specimen at a laboratory scale for prediction at the structural scale. The drying model is used to discuss the convection exchange coefficient between the material and the environment. For the surface exchange coefficient, both an analytical derivation and a numerical sensitivity study, especially regarding the size effect, are carried out. Then, the Biot-type dimensionless number called Surface Bulk Constant (SBC) is proposed to provide an improved understanding of the type of boundary conditions for moisture transport.

Automated summary

Assessing the moisture content evolution and drying shrinkage is crucial for the long-term operation of large concrete structures. This study evaluated the impact of size and boundary conditions on predicting mass loss and drying shrinkage of cement-based materials at ambient temperature. Experimental and numerical methods were used to examine the effects and validate the models' accuracy. Additionally, a new dimensionless number, Surface Bulk Constant (SBC), was proposed to enhance the understanding of moisture transport boundary conditions.