Modeling Anomalous Moisture Transport in Cement-Based Materials with Kinetic Permeability

Abstract

The durability of reinforced concrete structures is closely related to moisture state in cement-based materials. Therefore, it is crucial to develop moisture models that can accurately predict moisture state in the materials. However, many studies reported anomalous moisture transport in cement-based materials that cannot be well simulated by the conventional models. Several reasons have been investigated in the literature, such as the complex pore structure, chemical reactions with water, dimensional changes of the tested specimen, etc. Nevertheless, only a few models are able to capture the anomaly of moisture transport. This study viewed the main moisture transport coefficient—permeability—as a kinetic variable that depends on both the degree of moisture saturation and the contact time. The time-dependence was formulated by the decay (for drying) or growth (for wetting) functions. The saturation-dependence was calculated by the van Genuchten–Mualem (VGM) model. These functions were then implemented into a moisture transport model that was developed in previous studies. The proposed model was validated by experimental data and showed a good agreement for cement pastes that were dried or wetted in the hygroscopic range. Numerical simulation results were also compared with the simplified solutions to a fractional derivative model (FDM) of anomalous diffusion and the empirical Weibull function. We found that the solutions to the FDM cannot provide appropriate results. Weibull function performs as well as the proposed model, but the empirical function lacks physical meanings.

Corrosion of steel in carbonated concrete: mechanisms, practical experience, and research priorities – a critical review by RILEM TC 281-CCC

“…11), scientific advances are needed to quantitatively describe the phenomena related to moisture transport and retention in the carbonated cementitious matrix. Without doubt, progress was made in moisture transport modeling in concrete [81][82][83][84]. Nevertheless, there is a need to further develop these models, such as towards including moisture transport upon contact of the concrete surface with liquid water, and in particular to validate them against experiments performed with carbonated concrete.…”

The Physical Chemistry and Chemical Physics (PCCP) Section of the International Journal of Molecular Sciences in Its Publications: The First 300 Thematic Articles in the First 3 Years

“…Thematic Area 2 includes 22 articles, namely [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ], the typification of which is shown in Table 3 . With some degree of conventionality, it is possible to subdivide the articles published here into two main groups, namely, articles devoted to the study of the kinetics of processes in which any chemical transformations are decisive, and articles devoted to the study of the kinetics of processes in which chemical transformations are either not decisive or absent altogether.…”

“…From the list of articles cited above, in our opinion, one should also mention [ 30 , 43 , 45 ], which are remarkable in that, in each of them, the kinetics of any of the biochemical processes was studied (for example, in [ 45 ], the dissolution of self-organizing model peptide fibrils after quenching by dilution using the isothermal titration calorimetry method). Only works [ 34 , 39 , 40 ] are devoted to the study of the kinetics of reactions with the participation of inorganic compounds. In all these articles, however, some chemical reactions took place in one way or another, i.e., they all belong to the first of the above two groups of articles.…”

Effects of model boundary conditions on simulated drying kinetics and inversely determined liquid water permeability for cement-based materials

“…[15,16] The current approaches in the literature considering the microstructural effect on moisture transport is directly to write k l as a function of time, in which, the theory is that transport coefficients are directly related to materials' microstructure and the change microstructure is also a function of time; this group is known as the time-dependent models. [17][18][19][20] Another group considers the different transport speeds of moisture in different sizes of pores, so-called dual-permeability models. [21] Both of them can provide high accuracy simulation results.…”