Electrical Properties Of Concrete Research Articles

The Effect of the Waste of Materials and Carbon Nanotube on the Concrete Incorporated with Steel Fibers

The addition of agricultural and industrial solid wastes and nanomaterials to concrete combined with steel fibers to improve the mechanical and electrical properties of concrete was investigated. This approach could be used in advanced applications in electromagnetic shielding and conductive concrete. Steel fibers were used at 2%wt. of sand and (induction furnace slag (EIF), carbon nanotube (CNT), steel wool fibers, prepared corn husks) at 0.5 and 1 wt.%. of cement. Obtained results of using 1% for both carbon nanotube and steel wool with steel fibers in the mixture 4 and 6, respectively, showed the highest rates of compressive strength. A similar result was shown when tested at 3,7 and 28 days of age and compressive strength was 47.4MPa,47.34MPa for the mixture 4 and 6 respectively. The electrical conductivity and electrical resistance of the samples were measured at the age of 7 days. The findings have also shown that adding steel wool as well as( CNT) gave the best results and the sample containing the furnace slag achieved satisfactory results as well.

Cement paste with well-dispersed multi-walled carbon nanotubes: Mechanism and performance

The research of functional cement composite materials has always been the focus in the field of concrete. Multi-walled carbon nanotubes (MWCNTs) as one of the conductive fillers can significantly improve the mechanical and electrical properties of concrete. However, the addition of MWCNTs seriously affects the fluidity of cement paste and the distribution of internal particles, which limit the full potential of MWCNTs. In this paper, the dispersion mechanism and performance improvement of cement paste with well-dispersed multi-walled carbon nanotubes are systematically studied from the perspective of expanded DLVO (EDLVO) theory analysis, microscopic ESEM image observation and macroscopic performance measurement. The results of the EDLVO theory indicate that the polar interaction energy between MWCNTs particles is the main cause of agglomeration, and the entanglement of MWCNTs particles in cement paste are observed in ESEM images. The comparison of dispersants shows that under the same fluidity, the addition of polycarboxylate superplasticizer (PCE) guarantees better mechanical properties than sodium dodecyl sulfate (SDS). Experimental results of hardened cement paste with PCE show that at the age of 28 days, when the MWCNTs content is 0.1%, 0.3% and 0.5%, the flexural strength can be increased by 12.9%, 15.8% and 2.0%, respectively, and the resistivity can be reduced by 16.9%, 19.7% and 40.3%, respectively. Cement paste with well-dispersed MWCNTs obtains excellent mechanical and electrical properties, which lay a foundation for the utilization of MWCNTs in cement composite as the electrothermal materials in practical engineering.

On Providing an Assessment Monitoring System for Especially Essential Structures

The article deals with the assessment problems of especially essential structures. Increased demands on prevention of emergency situations and minimizing the consequences in the event of their occurrence require constant determination of especially essential structures condition. Achieving the goal of reliability and continuity of information is possible by coating the structure surface by a layer of electroconductive concrete, working as a monitoring system sensor. The study of the electrical properties of concrete was performed using the voltmeter – ammeter scheme. After the measurements had been made, the conditional electrical resistance of the electrode pair was calculated. The analysis of the above dependencies found that the change in the electrical resistance of the material from its stress approaches the linear law at lower values of W/C over a larger section of the studied interval. Processing of the obtained data showed that the measurement results were significantly affected by the shape and size of the electrodes used during the experiments.

Effects of Steelmaking Slag and Moisture on Electrical Properties of Concrete.

Strain sensors can indicate the conditions of concrete structures, but these sensors are only capable of measuring local behaviors of materials. To solve this problem, researchers have introduced conductive materials that can monitor the overall behavior of concrete structures. Steelmaking slag, which contains large amounts of iron oxide (Fe2O3), is conductive, and researchers have considered the addition of this material to improve concrete monitoring. In this study, mechanical and electrical properties of concrete containing steelmaking slag as a binder were evaluated. As the incorporation of steelmaking slag increased, the setting times were delayed, but the compressive strengths were similar within the replacement ratio of 15%. It was found that the addition of steelmaking slag with Fe2O3, the main ingredient of magnetite (Fe3O4), improved the electrical resistivity, piezoresistivity, and sensitivity of the concrete. Drying of the concretes resulted in an increase in electrical resistance and fractional change in resistivity (FCR). Expansion of steelmaking slag, due to contacting of free CaO and moisture under repeated loads, resulted in cracks in the concrete and affected the gauge factor (GF). This study demonstrates the possibility that the addition of steelmaking slag as a binder may provide an economical and environmentally-friendly solution to concrete strain monitoring.

Electrical and Self-Sensing Properties of Alkali-Activated Slag Composite with Graphite Filler.

The electrical properties of concrete are gaining their importance for the application in building construction. In this study, graphite powder was added to alkali-activated slag mortar as an electrically conductive filler in order to enhance the mortar’s conductive properties. The amount of graphite ranged from 1% to 30% of the slag mass. The effect of the graphite powder on the resistivity, capacitance, mechanical properties, and microstructure of the composite was investigated. Selected mixtures were then used for the testing of self-sensing properties under compressive loading. The results show that the addition of an amount of graphite equal to up to 10% of the slag mass improved the electrical properties of the alkali-activated slag. Higher amounts of filler did not provide any further improvement in electrical properties at lower AC frequencies but caused a strong deterioration in mechanical properties. The best self-sensing properties were achieved for the mixture with 10 wt% of graphite, but only at low compressive stresses of up to 6 MPa.

Electrical resistance of carbon-nanofiber concrete

Concrete is the most widely used construction material, and carbon nanofibers have manyadvantages in both mechanical and electrical properties such as high strength, high Young’smodulus and high conductivity. In this paper, the mechanical and electrical properties ofconcrete containing carbon nanofibers (CNF) are experimentally studied. The test resultsindicate that the compressive strength and per cent reduction in electrical resistance whileloading concrete containing CNF are much greater than those of plain concrete. Finally, areasonable concentration of CNF is obtained for use in concrete which not only enhancescompressive strength, but also improves the electrical properties required forstrain monitoring, damage evaluation and self-health monitoring of concrete.

Electrical conductivity of drying cement paste

Previous research has shown that electrical measurements can be used to monitor moisture movement inside concrete. The interpretation of these measurements is frequently based on empirical relationships between moisture changes and electrical properties of concrete. As such, these empirical relationships can limit the application of the electrical measurements to a specific material or exposure history. To facilitate the development of a general method that is applicable to a concrete member in service, this paper characterizes the electrical conduction in cement paste subjected to drying (desorption) and moisture absorption. The paper quantifies how the electrical conductivity is dependent on the volume and connectivity of the moisture inside the pores and the conductivity of pore solution. This paper also presents a procedure to quantify the contribution of the surface (solid-pore) conduction on the overall conductivity of the cement paste. The results of this investigation contribute to the development of an embedded relative humidity sensor that can be used to monitor changes in the internal humidity of concrete during its service life.

Analysis of power distribution in reinforced concrete during accelerated curing using electroheat

The problem of the distribution of heat in long curing beds used for the accelerated curing of concrete by electroheat is considered. A travelling wave solution is obtained for two configurations using experimental values of the electrical properties of concrete. From these solutions, recommendations are made regarding the optimal electrical layout to allow accelerated curing to be carried out while achieving the highest possible quality of the material.

Electrical conductivity of concrete containing silica fume

The influence of silica fume on concrete properties represents an important technical research. In general, silica fume tends to improve both mechanical characteristics and durability of concrete. Thus the electrical properties of concrete containing silica fume can be studied to clarify its physical performance during hydration. The electrical conductivity of neat cement, mortar and concrete pastes was measured during setting and hardening. The ordinary Portland cement was partially replaced by different amounts of silica fume by weight. The changes in the electrical conductivity were reported during setting and hardening after gauging with water. The results of this study showed that the electrical conductivity can be used as an indication for the setting characteristics as well as the structural changes of the hardened pastes made with and without silica fume.