3. electrical properties of hydrated cement-----relative permittivity, resistivity at various...
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Relative Permittivity:
The relative permittivity of a material is its dielectric permittivity expressed as a ratio relative to the permittivity of vacuum.
Relative permittivity is the factor by which the electric field between the charges is decreased relative to vacuum.
Relative permittivity is also commonly known as dielectric constant
Permittivity relates to the ability of a material to resist electric field
The permittivity of a medium describes how much electric field (or, flux) is generated per unit charge in that medium. More electric flux exists in a medium with a low permittivity (per unit charge) because of polarization effects, and vice versa.
Relative permittivity of a material, where ε(ω) is the absolute permittivity of the
material, and ε0 is the vacuum permittivity
Relative permittivity of Concrete (at r.t.p and under 1kHz) = 4.5
Resistivity:
Electrical resistivity is a property that quantifies how strongly a given material opposes the flow of electric current.
A low resistivity indicates a material that readily allows the flow of electric current.
Electrical resistivity, where R is the electrical resistance, is the length,
A is the cross-sectional area.
The Electrical Resistivity of a concrete varies at different moisture level:
Saturated between 10-100 Ω.m
Dry-Outdoors between 100-1,000 Ω.m
Dry-Indoors between 1,000-10,000 Ω.m
Oven-Dry about 1,000,000 Ω.m