Non-destructive Electrical Methods for Measuring the Physical Characteristics of Porous Materials

Abstract

The durability of reinforced concrete structures, built on the seafront, has been at the heart of recent concerns. Indeed, chloride transport across the porosity of concrete coating produces medium to long-term corrosion of reinforcements. This has a direct impact on the mechanical behavior and the ageing of the affected structures. The difficulty of in situ monitoring of these structures, continuously and non-destructively against infiltration of chlorides, is still topical. The work presented here aims mainly at correlating the electrical properties, i.e. electrical resistance, conductivity…, with the physical characteristics (porosity, tortuosity, ...), of granular materials using Archie's law. The recommended experimental program consists in placing, different granular materials, i.e. sand, mortar, bricks, and concretes saturated with electrolytic solutions, in a PVC cell fitted with a pair of stainless steel electrodes connected to an electrical circuit, in order to measure the electrical resistances. The results obtained allow one to determine durability factors, such as the connected porosity and the coefficient of chloride diffusion through a simple measurement of the EC, and estimate the tortuosity parameter that governs transport in porous media.

Experimental Examination of Electrical Characteristics for Portland Cement Mortar Frost Damage Evaluation

“…According to Archie's law [24], the formation parameter can be replaced by the porosity with a power law. From Merioua et al [23], for mortar with W/C equal to 0.5 m is approximately 3.…”

“…The frequency of the alternating current can affect the resistivity results significantly [26]. As investigated by Merioua et al [23], to assure the ohm's law is valid, the range of appropriate frequencies is 500 Hz-50 kHz. Additionally, the polarization effect can greatly affect the resistivity and it is highly dependent on frequency; to reduce the effect to be minimum, the frequency used in this study was 1 kHz, which is the optimized frequency reported by McCarter et al [35] on the study of concrete under FTCs.…”

“…For the fully-saturated samples, before exposure to the FTCs, the electrical conductivity of sample is determined by the electrical conductivity of the pore solution and the formation parameter [22,23] as below:…”

“…It is believed that the electrical resistivity of concrete is related to the pore characteristics, saturation degree, temperature and pore solution compositions [22]. The relationship between the electrical conductivity of concrete and the porosity can be expressed as modified Archie's law [23]. Moreover, the moisture effect to electrical resistivity can be quantified by Archie's law [22,24], and the temperature effect can be described by the Arrhenius equation and the activation energy is the index for evaluation [25][26][27][28].…”

A testing methodology for performance-based specification

“…The specification of the service-life/performance/durability of reinforced concrete by means a single parameter is the holy grail of the engineer and hence a subject of intense research interest (see, for example, Neithalath, Persun, and Manchiryal, 2010;Muigai, Moyo and Alexander, 2012;Spragg et al, 2013;Andrade, d'Andrea and Rebolledo, 2014;Nganga, Alexander and Beushausen, 2015;Merioua, Bezzar and Ghomari, 2015). The challenges posed by a performance-based testing and specification approach to improve service life of concrete structures have been acknowledged (Beushausen and Fernandez-Luco, 2015).…”