Frequency- and Time-Domain Dependency of Electrical Properties of Cement-Based Materials during Early Hydration

Abstract

The electrical properties of Portland cement, and cements containing supplementary cementitious materials (SCM), were obtained over the frequency range 1kHz-10MHz during the initial 24-hours after gauging with water. The response was measured in terms of conductivity and permittivity with both parameters exhibiting significant temporal changes during this period. It was also evident that whilst the conductivity increased only marginally with increasing frequency of applied electrical field, the permittivity decreased by several orders of magnitude over this frequency range. Moreover, certain features of the permittivity response-which are related to bulk polarization processes-only revealed themselves in the higher frequency range (100kHz-1MHz), and went undetected at lower frequencies. The detailed frequency-and time-domain measurements allowed identification of several stages in the early hydration of cement-based materials and the response can be interpreted in terms of hydration kinetics, physico-chemical processes and microstructural development. It is shown that the methodology can be equally applied to cement-pastes and concretes.

Electrical Resistivity and Electrical Impedance Measurement in Mortar and Concrete Elements: A Systematic Review

“…The measurement of electrical impedance of concrete should be performed according to the EIS method, thus spanning multiple frequencies. This is of utmost importance, since the material electrical properties (both the electrical resistivity and the dielectric permittivity) are frequency-dependent [69] and the analysis in different ranges allows to investigate several different aspects of materials (e.g., the composite resistance of specimens with conductive fibers is visible at a higher frequency, since at low frequency the superficial passive layer makes them non-conductive [22]). The results of an electrical resistivity measurement are strictly linked to the frequency and the shape of the electric signal used for the measurement.…”

“…However, there are no general statements on optimal frequency to be used and both sine and square waves are deployed. In fact, it is worth noting that materials electrical properties are frequency-dependent [69] and, consequently, the measurement frequency deeply affects the results.…”

Insights into the piezoceramic electromechanical impedance response for monitoring cement mortars during water saturation curing

“…E: Applied electrical field. σ: Stress vector (N/m 2 ). e σ : The dielectric permittivity matrix at constant stress (Farad/ m).…”

“…Prior knowledge of on-site strength development in real-time can help accurately predict formwork removal time, and mitigate against accidental damage caused by premature loading. Ultrasonic methods, monitoring electrical properties of hydrating cementitious materials, and monitoring hydration temperature [1,2] are all mature techniques that fulfil automation and remote strength development monitoring requirements. However multifunctional, cost-effective and yet easy-to-use sensors which can be deployed at different project phases, i.e.…”