Calculation of the Bulk Resistivity
Resipod displays a number in kΩcm. The number obtained from the Resipod display should be
divided by 2πa (where “a” is the probe spacing, i.e. either 3.8 cm or 5.0 cm). For a Resipod with
38mm probe spacing:
Cylinder size 2πa A (cm2) L (cm) A/L (cm)
4x8 23.88 81.07 20.32 3.99
The bulk resistivity ρ = K
x R
cylinder
, where K = A/L
Example
R
cylinder
= 52 kΩcm
R
cylinder
(corrected) = 52 / 23.88 = 2.18 kΩ
Bulk resistivity ρ = K x R
cylinder
= 2.18 x 3.99 = 8.69 kΩcm
Bulk Resistivity in ResipodLink
ResipodLink offers the possibility to calculate K automatically and download it onto the Resipod
instrument, so that the display shows directly the correct value in kΩcm. See Chapter 9.
5.2 Resipod Geometric
Resipod Geometric is supplied with a stand for mounting the Resipod and a variable spacing
probe that allows probe spacing to be varied between 40mm and 70mm. This allows it to accom-
modate larger aggregate sizes.
The ResipodLink software (Chapter 9) allows the user to enter the correct probe spacing and also
a geometric correction factor to give the correct resistivity reading directly on the instrument.
The geometric correction factor for cylinders is designed to comply with the latest research in-
tended to extend the current AASHTO surface resistivity method to other sample geometries.
In addition to this the user also has the possibility to enter a self-determined correction factor.
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