Standard Test Method for Bulk Electrical Resistivity or Bulk Conductivity of Concrete

Importancia y uso:

5.1 The electrical resistivity of a concrete is the opposition to the movement of ions under an applied electric field. The electrical conductivity of a concrete is a measure of how readily the ions in the pore solution can be transported through the concrete under an applied electric field (the higher the conductivity, the greater the rate of transport). The electrical resistivity or conductivity is a material property that depends upon the pore volume, the pore structure (size and connectivity), the pore solution composition, the degree of saturation of the concrete specimen, and the specimen’s temperature. Concrete mixture characteristics that are known to affect concrete electrical resistivity, as well as resistance to chloride ion penetration, include water-cementitious materials ratio, pozzolans, slag cement, the presence of polymeric admixtures, air-entrainment, aggregate type, aggregate volume fraction, degree of consolidation, curing method, and age.

5.2 The bulk electrical resistivity of concrete is the inverse of its bulk electrical conductivity. Bulk electrical conductivity can also be measured by Test Method C1760, which uses the apparatus described in Test Method C1202. This test method, however, uses apparatus specifically designed to measure bulk conductivity or bulk resistivity.

5.3 The standard conditioning in this method is in a simulated pore solution. The purpose of conditioning in a simulated pore solution is to limit leaching of alkalis, and calcium hydroxides. Saturated lime water minimizes calcium hydroxide leaching but does not prevent alkalis leaching. Both simulated pore solution and saturated lime water bring the specimen to a level of near complete saturation of pores. When comparing two different concrete specimens, it is important to condition both specimens as close as possible to a comparable saturation state, using the same solution for conditioning, so that values can be compared in a meaningful way. This is particularly true for using the measured resistivity or conductivity, along with other information, to estimate the diffusivity.

5.4 The bulk electrical resistivity or conductivity of concrete can provide a rapid indication of its resistance to chloride ion penetration and resistance to penetration of other fluids. Resistivity or conductivity measurements have shown good correlations with other electrical indication tests including Test Method C1202 (1, 2, 3).6 Bulk electrical resistivity results have shown good correlation with bulk diffusion determined using Test Method C1556 on companion molded cylinders from the same concrete mixtures (4).

Subcomité:

C09.66

Referida por:

C1952-25

Volúmen:

04.02

Número ICS:

91.100.10 (Cement. Gypsum. Lime. Mortar)