Common methods of controlling setting, hardness, process of strength growth of concrete are tests for determining the setting time of mortar (ISIRI 392) and concrete (ISIRI 6046) and determining the compressive strength of concrete (ISIRI 3206). Since these physical and mechanical methods do not fully reflect the behavior of concrete and also it’ s time and money consuming, application of electrical resistance of concrete has been investigated. Therefore, in this study, an extensive laboratory operation was designed. In the first stage, 11 samples of cement were prepared, the phases of which varied, but due to laboratory cementation, their fineness and grading were almost the same. Physical and chemical analysis of cement samples were performed. In the next step, 22 concrete mixtures with 11 cement samples were prepared, so that 11 mixtures with the title of control (without additives) and 11 mixtures with constant dosage of commercial super plasticizer (based on poly carboxylate). Compressive strength tests has been performed at ages of 7, 28 and 90 days. Also, an electrical resistance test was performed, which was performed regularly from the time of cement contact with water until 31 days later. The results showed that at least three peaks of 8, 16 and 23 days in the electrical resistance curve are seen along the test time. In almost all samples, the electrical resistance is reduced to about 3 hours, which indicates the setting time of the concrete. Based on the results of this study, formula was presented.

One of the main factors of premature deterioration of concrete structures is the corrosion of reinforcements. Chloride penetration of concrete is one of the main reasons of this phenomenon. Therefore, to have durable structure, it is necessary to have concretes with low permeability. There are various methods to evaluate permeability of concrete. Finding a relationship between them can be useful for understanding the mechanism of corrosion. Concrete resistivity test is a suitable indicator for concrete penetration and chloride ion permeability. It is a non-destructive, simple, rapid and cheep method that can also be used in site. In this study, various permeability and resistivity tests were carried out on different types of concrete to find a relationship between them. In addition, the main factors affected the resistivity are disgusted and the major constraints of relation between resistivity and permeability of concrete are illustrated. Finally, a new method is recommended to eliminate these problems.

Nondestructive physical tests can be considered as recent trends for quality evaluation of agricultural products. Required information on postharvest quality of fruits and vegetables makes it possible to use their electrical properties as a novel method for nondestructive quality evaluation purposes. In this study, the electrical resistance of harvested apple fruits (Golden Delicious variety) was nondestructively measured by developing and employing special plate electrodes using a load cell to adjust the force holding the samples between two electrodes. Electrical resistance measurements were performed at two frequencies; 120 Hz and 1 kHz. Precise fruit weight was also measured along with electrical resistance measurements. The relationship between the electrical resistance and the weight loss was investigated during the storage period. The experiment ran for a total of 24 days. Results showed that in the 15 initial days of experiment, the electrical resistance decreased by increasing the storage period. But with further increase in the storage period, the electrical resistance also increased. The loss of the fruit moisture content, during the early stage of storage, may be attributed to the decrease of the fruit electrical resistance. However, as the stored apples lost more moisture, the concentration of ions, in soft tissues of samples, highly increased and this could be responsible for the increase of apple electrical resistance during the final days of the experiment.

The study of the physical properties (geophysical methods) of rocks associated with its mechanical properties has recently received lots of attention. Recent studies show that geophysical methods especially the seismic and geoelectric methods are able to estimate the mechanical parameters and recognize their spatial variations, including anisotropy. Meanwhile, electrical and seismic methods are the most used one.Electrical measurement is one of the non-invasive geophysical methods commonly used by engineers working in various fields such as mining, geotechnical, civil, underground engineering as well as oil and gas mineral explorations. This method can be applied both in laboratory and in the field. Numerous scientists have focused on the relation between resistivity and porosity. However, there is a very limited study on the relation between the electrical resistivity and the rock properties apart from porosity.In this paper, changes in the electrical conductivity of rocks during a uniaxial compression test were investigated in laboratory. The uniaxial compressive strength, elastic modulus, and density values of the samples were determined in laboratory. We installed special electrodes on seven nearly saturated core samples in order to measure the resistivity. Core samples had a 52-mm diameter and a 110-mm length. Two-electrode as well as four-electrode arrays were both used in resistivity monitoring in laboratory. Using a four-electrode array minimized the undesirable electrode polarization effects. In the four-electrode array, we used two non-polarizing Ag/AgCl electrodes mounted on the core sample. Our laboratory observations showed that there was not any electrode polarization effect. When we used a two-electrode array, the resistivity changes were less than 5 percent compared to a four-electrode array. In our laboratory investigation, we used different sedimentary core samples including sandstone, fossilioferous limestone and travertine. Maximum resistivity observed for the travertine core sample was less than 12 kohm. During the uniaxial compressive test, deformation measurements were made and the stress–strain curves were plotted. Tangent Young’s modulus values were obtained from stress–strain curves at a stress level equal to 50% of the ultimate uniaxial compressive strength.Sandstone core samples showed a resistivity increase in the whole strain range. On the contrary, the fossiliferous limestone samples (thin section showed that the sample was composed of tiny calcium fossils in a fine aggregate of micrite cementation) showed a resistivity decrease in the whole strain range. Travertine and limestone showed an intermediate behavior (resistivity increased in the lower strain and it decreased in the higher range). In other words, the onset of new crack formation occurs well inside the quasi-linear part of the stress-strain curve. The quasi-linear portion of the stress-strain curve was the result of a competition between closure of one population of cracks, and the growth of new propagation of the existing cracks.Resistivity behavior during a uniaxial compression load is closely related to the pores in the lower strain ranges and then to the new induced fractures in higher strains. Our results showed that the electrical resistivity may be a representative measure of the rock properties. Additionally, the effect of certain minerals on the rock’s resistivity must be taken into account. The results indicated that the rock structure had an important effect on the resistivity behavior during a mechanical loading.

In this study with the help of master curves of dipping beds, we try to find the dip of the layer and its elongation on depth. This study has helped us to choose best place for geotechnical borehole logging. Of course, we know that these master curves could not answer our question for depth more than about 60 meters.The further correction will be made with the help of geological data, since available curves are suitable for homogeneous and isotropic Earth. These curves will be used for dipping layer with dip angle more than 20°.Early curves were calculated for two dipping layers. The best results were found when reflection coefficient is 1 and -1.In this study we try to use these curves in the field. The field is Shorbulagh village near Karaj city for Dam construction. In this site there are three layers with 43° dip angle, sandstone and mudstone with reflection coefficient about -0.94. Four soundings were done with Schlumberger array, and the curves interpreted and the errors were shown.