Relating unsaturated electrical and hydraulic conductivity of cement-based materials

Abstract

Unsaturated hydraulic (K) and electrical (σ b ) conductivity are often considered durability indicators of cement-based materials. However, K is difficult to measure experimentally. This is due to the large pressure requirements at low degrees of saturation resulting from the fine pore-size distribution of cement-based materials. As a result, the commonly-used analytical models, requiring calibration of K from experimental data, are often inaccurate at low degrees of saturation. On the other hand, measuring σ b is rather straight forward. Descriptions of the relationship between σ b and K may therefore be particularly valuable when K is required. In this work, we use experimental data from previous works to determine the feasibility of models employing a van Genuchten-Mualem based framework to predict K and σ b -expressions for diffusivity D are also provided. We then develop analytical expressions relating K and σ b using these models. It is then shown that K = K(σ b ) and σ b = σ b (K) may be determined when either parameter is fully described. Lastly, we propose a simplified model and discuss the roles of pore-size distribution, saturation, pore connectivity and tortuosity in characterizing the relationship between K and σ b .

Joint inversion of electromagnetic measurements for the determination of water saturation profiles in concrete structures

“…Eq. ( 6) is consistent with Archie's empirical law, proposed in 1942 by geologists in the oil prospecting field for non-clayey rocks [48], and then for porous materials such as concrete [9,10,49,11]. The dielectric permittivity was shown to increase linearly with [50,51,25]:…”

“…Previous studies have shown that the electrical resistivity, , is sensitive to the change of concrete saturation degree, , which is a prominent durability indicator [5,6,7]. This sensitivity could be established by an experimental calibration law between and [8,9,10,11]. Nonetheless, an inversion of the measurements needs to be carried out to estimate the resistivity of concrete.…”

Spectral induced polarization of low-pH cement and concrete

“…In the future, it would be very interesting to numerically solve the Poisson-Nernst-Planck equations to improve the accuracy of the resistivity models and consider polarization of steel reinforcement in concrete structures. Laboratory SIP studies for cement-based materials in partially water-saturated conditions, which are much closer to actual field conditions [156], should also be investigated. where r is the radial coordinate from the pore center (m),  is the electrostatic potential in the EDL (V), 0 J is the zero order Bessel function, and κ is the inverse of the Debye length (m -1 ).…”

Electrical tomography for characterizing transport properties in cement-based materials: A review

“…) generated from ET reconstructions one could, for example, estimate the hydraulic conductivity K using analytic relations from [69].…”

“…Obviously, cement-based materials are a new material relative to geologic and human histories; therefore, it is rather intuitive that transport research in geologic materials was well established before transport research in cement-based materials. As such, the modern understanding of unsaturated transport in cement-based materials is largely owed to researchers in geophysics and soil science [69]. In the following, we will jump forward from the fundamentals of transport in porous media and continue by reviewing the developments leading to modern-day usage of ET for characterizing transport in cement-based materials.…”