Bulk Resistivity Measurements Research Articles

Self-sensing nano-engineered ultra-high performance concrete (UHPC) under tension

With the addition of electrically conductive steel or carbon fibers, Ultra-High-Performance Concrete (UHPC) possesses an intrinsic self-sensing capability. This opens up the possibility of combining the resilience and sustainability of UHPC with the development of self-sensing solutions for structural applications. In this study, the self-sensing behaviour of a proprietary nano-engineered UHPC material subjected to tension was investigated. To assess the self-sensing performance of the material, bulk resistivity measurements were used on direct tension and pure flexure tests, while a novel wireless approach that operates on was used on out-of-plane bending tests. The wireless approach used alternate current (AC) measurements while the bulk resistivity methods were performed through direct current (DC) and the four-probe method. In both methods, the fractional change in resistance was correlated to the state of deformation. The disposition of the actual strain field was evaluated using Digital Image Correlation (DIC). It was found that in the case of direct tension and pure flexure, the fractional change of resistance was initially decreased up to the onset of strain localization, while it gradually increased in the post-peak range, where the separation of the localized crack gradually increased. In the case of the wireless approach using AC, the onset of cracking was successfully predicted with an abrupt increase in resistivity. The wireless strain-sensing approach also captured the Poisson’s effect due to the loading.

Estimation of non-traditional supplementary cementitious materials potential to prevent alkali-silica reaction using pozzolanic reactivity and bulk resistivity

Relationships between supplementary cementitious material (SCM) pozzolanic reactivity, bulk electrical resistivity, and alkali-silica reaction expansion were examined for traditional and non-traditional SCMs using the modified R3 test, bulk resistivity measurements, and the accelerated mortar-bar test (AMBT), respectively. The SCMs included pozzolanic pumice and glass powder and latent hydraulic slag, with cement and limestone fillers being tested as controls. For mixtures with SCMs, as fineness, reactivity, or replacement level increased, bulk resistivity increased, and the ASR expansion decreased; this was not the case for limestone. Strong correlations between pozzolanic reactivity, bulk resistivity, and ASR expansion suggest the ability to estimate expansion based on reactivity and resistivity, although ASR expansion is a more complex phenomenon. By increasing the curing temperature, 1-day bulk resistivity measurements could be used to estimate ASR expansion. Threshold values for bulk resistivity and pozzolanic reactivity were proposed for screening materials and mixtures, including novel ones, for ASR durability.

Magnetic and electronic structures of antiferromagnetic topological material candidate EuMg2Bi2

EuMg2Bi2 has been investigated to understand the electronic and magnetic behaviors as an antiferromagnetic (AFM) topological semimetal candidate. High-quality single crystals of EuMg2Bi2 were grown via a Bi flux and, subsequently, characterized to be consistent with the previously reported bulk magnetic and resistivity properties. A ferromagnetic interaction is indicated by the positive Curie–Weiss temperature obtained through fitting the bulk magnetic susceptibility data. The bulk resistivity measurements reveal an interesting electronic behavior that is potentially influenced by a competing antiferromagnetic and ferromagnetic interaction in and out of the ab plane. From the resulting refinement of the neutron diffraction data, EuMg2Bi2 was found to exhibit an A-type magnetic structure with Eu2+ moments ferromagnetically aligned in the plane and antiferromagnetically stacked between neighbor ferromagnetic Eu layers. The power law fitting magnetic ordering parameter below TN ∼ 8 K agrees with the 2D Heisenberg model, indicating a weak interlayer antiferromagnetic interaction. Considering the magnetic structure determined by neutron diffraction, the surface state calculation suggests that EuMg2Bi2 is an AFM topological insulator candidate. Linearly dispersed Dirac surface states were also observed in our angle-resolved photoemission spectroscopy measurements, consistent with the calculation.

High-rate timing resistive plate chambers with ceramic electrodes

We describe recent advances in developing radiation-hard ceramic resistive plate chambers (CRPCs) with Si3N4/SiC composites. Bulk resistivity measurements for this material for different manufacturing processes are reported. The results show that the bulk resistivity ρ can vary between 107and1013Ωcm. The varistor type behaviour of the material is analysed. A comparison with other materials used in timing RPCs is given. We describe the assembly and tests of CRPC prototypes in electron and proton beams. For a prototype with ρ~5×109Ωcm, the efficiency of the detectors is 95% at a flux of 2×105cm−2s−1. The time resolution at the same flux is about 120ps. A prototype with ρ~2×1010Ωcm shows an efficiency of about 85% up to fluxes of 5×104cm−2s−1 with a time resolution better than 80ps. The results are compared with RPC models.

Two-point concrete resistivity measurements: interfacial phenomena at the electrode–concrete contact zone

Ac impedance spectroscopy measurements are used to critically examine the end-to-end (two-point) testing technique employed in evaluating the bulk electrical resistivity of concrete. In particular, this paper focusses on the interfacial contact region between the electrode and specimen and the influence of contacting medium and measurement frequency on the impedance response. Two-point and four-point electrode configurations were compared and modelling of the impedance response was undertaken to identify and quantify the contribution of the electrode–specimen contact region on the measured impedance. Measurements are presented in both Bode and Nyquist formats to aid interpretation. Concretes mixes conforming to BSEN206-1 and BS8500-1 were investigated which included concretes containing the supplementary cementitious materials fly ash and ground granulated blast-furnace slag. A measurement protocol is presented for the end-to-end technique in terms of test frequency and electrode–specimen contacting medium in order to minimize electrode–specimen interfacial effect and ensure correct measurement of bulk resistivity.

On the limitations of predicting the ohmic resistance in a macro-cell in mortar from bulk resistivity measurements

An experimental setup was designed to simulate the conditions for chloride-induced macro-cell corrosion, in which small anodes are located in a large network of cathodes. The overall aim of the present study was to assess whether measuring the bulk resistivity of reinforced concrete/mortar can give sufficient information about the resistance between anode and cathode inside a macro-cell. Measurements were executed in mortar specimens with high and low resistivities. Both the resistance in the simulated corrosion cells and the bulk resistivity of the mortar mixtures were determined. A comparison of the results showed no direct correlation. This indicates that the common practice of comparing bulk resistivity with corrosion rate may not be sufficient to characterize the corrosion process of chloride induced macro-cell corrosion.

Correlation Between Bulk and Surface Resistivity of Concrete

Electrical resistivity is an important physical property of portland cement concrete which is directly related to chloride induced corrosion process. This study examined the electrical surface resistivity (SR) and bulk electrical resistivity (BR) of concrete cylinders for various binary and ternary based high-performance concrete (HPC) mixtures from 7 to 161 days. Two different types of instruments were utilized for this investigation and they were 4 point Wenner probe meter for SR and Merlin conductivity tester for bulk resistivity measurements. Chronological development of electrical resistivity as well as correlation between two types of resistivity on several days was established for all concrete mixtures. The ratio of experimental surface resistance to bulk resistance and corresponding resistivity was computed and compared with theoretical values. Results depicted that bulk and SR are well correlated for different groups of HPC mixtures and these mixtures have attained higher range of electrical resistivity for both types of measurements. In addition, this study presents distribution of surface and bulk resistivity in different permeability classes as proposed by Florida Department of Transportation (FDOT) specification from 7 to 161 days. Furthermore, electrical resistivity data for several HPC mixtures and testing procedure provide multiple promising options for long lasting bridge decks against chloride induced corrosion due to its ease of implementation, repeatability, non-destructive nature, and low cost.

Electrical transport properties of manganese containing pyrochlore type semiconducting oxides using impedance analyses

A new series of manganese containing pyrochlore type semiconducting oxides CaCe1−xMnxSnNbO7−δ (x=0, 0.2, 0.4 and 0.6) have been synthesized to study the effect of Mn substitution on the structure, microstructure and electrical properties of these samples. X-ray diffraction and scanning electron microscopy studies revealed an increase of structural ordering and grain size respectively with increase of Mn substitution. Rietveld analysis and Raman spectroscopy were also employed to corroborate the XRD results. The bulk resistance measurements with temperature exhibit negative temperature coefficient behavior. The impedance analysis of the samples revealed a non-Debye type relaxation existed in the materials. The ac conductivity variation with temperature and frequency indicates a correlated barrier hopping type conduction mechanism in these materials. The barrier height and the intersite separation for hopping influence the electrical conductivity of these samples and are found to be a function of localization of electrons associated with the Mn2+ ions and the unit cell volume respectively. The Mn substitution increases both electrical conductivity and activation energy contrastingly. This unusual behavior has been explained by correlating the structure, microstructure, defect states, electron localization and intersite separation with the conductivity data of the samples.

Accurate measurement of electrical bulk resistivity and surface leakage of CdZnTe radiation detector crystals

A classical method for the accurate measurement of the bulk resistivity and a quantitative separation of bulk and surface leakage currents in semi-insulating CdZnTe radiation detectors is evaluated. We performed an extensive set of experiments on CdZnTe single-crystal test devices to confirm the reliability and reproducibility of the measurements and the validity of the underlying assumptions for data analysis and parameter extraction. The experiments included temperature dependent dual current-voltage measurements on devices with guard electrodes as a function of device thickness, surface preparation, surface passivation, and electrode deposition conditions. We also evaluated the temperature dependence of the bulk resistivity and implemented a general temperature normalization routine to allow a reliable comparison between various crystal samples.

Mapping of the hyporheic zone around a tidal creek using a combination of borehole logging, borehole electrical tomography and cross-creek electrical imaging, New South Wales, Australia

A combination of electrical imaging carried out across a tidal creek and borehole electrical tomography between strings of electrodes installed in bores adjacent to the creek is used to establish the shape of the hyporheic zone beneath a tidal creek in a sand aquifer. The interpretations provided by the data inversions are checked against fluid electrical conductivity (EC) samples collected from bundled piezometers installed in the creek banks and from bulk EC measurements made using induction logs in bores on the creek banks. Extensive seepage into the base of the creek is identified from the electrical image and verified by independent measurements of hydraulic head and fluid EC. The Effective Medium Theory is used to derive values of fluid EC from bulk resistivity measurements obtained from the inversion process. The data show an extensive zone of mixing between seawater and rainwater recharge into the aquifer, with the shape of the hyporheic zone strongly influenced by regional groundwater discharge and the presence of a thin layer of cemented sands at a depth of 10 m. The combined interpretation demonstrates the importance of borehole control in the interpretation of electrical images measured from the surface over complex EC distributions.

WATER CONTENT ASSESSMENT OF FRESH CONCRETE.

Compliance testing of concrete forms an integral part of an overall quality control strategy in the production of concrete. There are two aspects of testing to consider: tests undertaken while concrete is still in the flowing state; tests undertaken when concrete is in the hardened state. Regarding the former, a considerable number of tests are available ranging from traditional, empirical methods such as the slump test, to more sophisticated methods such as nuclear magnetic resonance and microwave absorption. In this paper, attention is directed towards concrete while still in the fresh state, and developments in an electrical method for water content evaluation are presented. It is shown that when bulk resistivity measurements on concrete are normalized by that of the interstitial water phase, then the water content of the fresh concrete can be assessed. (A)

Borehole‐to‐surface electrical resistivity monitoring of a salt water injection experiment

A field experiment was conducted at the University of California Richmond Field Station to demonstrate the sensitivity of borehole‐to‐surface resistivity measurements in groundwater investigations. A quantity of saline water was injected into a fresh water aquifer while the resistivity was monitored using a multichannel borehole‐to‐surface system. Two experiments were conducted using pole‐pole and pole‐dipole receiver electrode arrays. The data from the pole‐pole experiment were superimposed to simulate a dipole‐pole array and the data from the pole‐dipole array were superimposed to simulate a dipole‐dipole array. This superposition of the data was done to enhance the anomaly and facilitate interpretation. A numerical modeling study was performed in conjunction with the field experiment in order to interprete the results. A three‐dimensional modeling program was used to simulate the geological setting of the field experiment and the salt water injection. This modeling revealed that an asymmetric displacement of the salt water slug results in asymmetric current channeling which is observable as a 25 to 40 percent difference between preinjection and postinjection borehole‐to‐surface resistivity. In addition to demonstrating the sensitivity of subsurface arrays, this experiment demonstrated that the measurement of bulk resistivity can identify a groundwater flow pattern not detected by hydrological measurements.

Effect of post-sintering quenching parameters on Tc and crystal structure of the Bi2Sr2CaCu2O8+δ (2212) phase

Effects of post-sintering cooling rate from liquid quenching to slow air cooling were investigated for the low- T c 2212 phase in the Bi-Sr-Ca-Cu-O system. The fastest cooling rate yielded the 2212 granular phase with the highest superconductive T c . The change in T c is attributed mainly to the change in oxygen stoichiometry. The difference between the granular and bulk T c 's was smallest after slow cooling, even though the granular T c then had its lowest value. No variation in lattice parameters was observed by powder X-ray diffraction. When the samples were quenched, structural imperfections were introduced; these could not be eliminated even by long-term annealing and slow cooling in air. The lowering of T c was inhibited by the presence of these imperfections in the crystal structure of the 2212 phase. It is emphasized that the true granular superconductive properties are best observed by magnetic measurements since bulk resistivity measurements may lead to erroneous conclusions.

Mobility of Na + in PVC membranes containing valinomycin and di-benzo-18-crown-6

We report bulk resistance measurements on PVC membranes containing varying proportions of NaBPh 4 and either valinomycin or di-benzo-18-crown-6. From an analysis of these measurements we have been able to demonstrate the lower mobility of Na + when complexed by valinomycin or di-benzo-18-crown-6 compared with “bare” Na +.

Transient-current study of field-assisted emission from shallow levels in silicon

Transient currents due to the emission of carriers trapped on shallow doping levels are investigated in silicon junctions at low temperature. The current-vs-time curves present a peak which can be explained in terms of electric field activation. Simultaneous bulk resistivity measurements allow determination of a temperature range where the transient currents can be properly analyzed, i.e., between 20-25 K. The detrapping kinetics are then analyzed mathematically and the different possible electric field activation mechanisms reviewed: shallow-impurity impact ionization, Frenkel-Poole effect, tunneling, and phonon-assisted tunneling. Three-dimensional calculations are performed for these last two effects and tractable expressions are derived. In Si:P junctions, fairly good agreement between the theoretical model and experimental data is obtained for Frenkel-Poole effect only. In Si:B junctions, an electric-field-dependent peak is observed for ionization transient currents, but it is too broad to be fitted. This is shown to be due to the very high resistivity of our $p$-type samples in the temperature range investigated. Finally, the value obtained for the electron-capture cross section on phosphorous is discussed.

Simple method of measurement of bulk resistivity of soil : Richards, M L; De Sa, A Sci Instr (j Phys E), V10, N12, Dec 1977, P1218–1220

Simple method of measurement of bulk resistivity of soil : Richards, M L; De Sa, A Sci Instr (j Phys E), V10, N12, Dec 1977, P1218–1220

A simple method of measurement of bulk resistivity of soil

A simple method of measurement of bulk resistivity of soil using an autoranging digital voltmeter is described. The apparatus is battery-operated, portable and weighs only 6 kg. It can be easily constructed using readily available integrated circuits and other electronic components. The use of the method in conjunction with digital data-processing techniques in an archaeological survey is demonstrated.