Abstract
A method for measuring the volume of a solid with arbitrary shape and the open porosity (volume fraction of the open pores) of air-saturated porous materials is proposed. The experimental principle is inspired from Beranek’s method [J. Acoust. Soc. Am. 13, 248 (1942)] based on the application of the ideal gas law to the gas surrounding the solid. The originality of the proposed method lies in the comparison of the volume of a measurement chamber containing the sample with that of an empty reference chamber. During a measurement, the reduction of volume in the measurement chamber due to the introduction of the solid is compensated by increasing the volume of a piston connected to the measurement chamber. An important aspect of this experimental system is that the influence of temperature can be considerably reduced as nearly the same variations of temperature apply simultaneously to the measurement and the reference chambers. A preliminary calibration experiment without sample in the measurement chamber is carried out in order to equalize the volumes of the two chambers. The calibration can be performed once and for all, thus minimizing the number of operations in the measurement process. The porosities of several materials are measured and compared to reference values. The precision and possible future improvements are discussed.
Highlights
The porosity of a porous material corresponds to the volume proportion of fluid contained in the pores, i.e., the total volume of the fluid in the pores divided by the volume of the sample
A calibration experiment is carried out first in order to equalize the volumes of the reference chamber and the measurement chamber in the absence of sample and with the measurement piston to zero
There was no alternative method to which to compare the sizes of the measurement chamber and of the porous samples result as saturating the grains with water posed the problems are limited, improving the precision requires increasing the of damage to the sample and modification of its porosities. precision of the value read on the measurement piston as
Summary
The porosity of a porous material corresponds to the volume proportion of fluid contained in the pores, i.e., the total volume of the fluid in the pores divided by the volume of the sample. It is an essential parameter in the physical and acoustical modeling of porous media. A method for measuring the porosity of air-saturated materials with reduced thermal effect is proposed. The method proposed in this article is based on the compressibility of the air in the connected pores and this method yields the open porosity
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