Analysis of porous material using laboratory calibrated test apparatus and sample data
Test apparatus for testing porous material such as used in roadway base or building foundations may be deployed in the field at various test sites. The test apparatus includes electrodes that contact the porous material under test and a sensor unit that supplies electromagnetic signals to the porous material. Response signals reveal electrical parameters such as complex impedance which can be equated to material properties such as density and moisture content. Reference may be made to empirical correlations made in laboratory tests using the same test apparatus to enable the effects of the test apparatus on the measurement to be accounted for. The electrodes may include flexible coplanar electrodes that reduce air gaps when in contact with the porous material.
1. A method for testing a porous material under test at a field site, the method comprising:
(A) determining empirical data correlating at least one of capacitance, conductance and complex impedance for the material with at least one of density and moisture content, comprising:
(a) placing the material in a standard proctor mold;
(b) compacting the material in accordance with a standard;
(c) measuring the at least one of density and moisture content according to the standard;
(d) connecting a test apparatus comprising one or more electrodes to the proctor mold;
(e) measuring at least of the capacitance, conductance and complex impedance of the material in the mold; and
(f) storing a correlation between the measured at least one of density and moisture content and the measured at least one of capacitance, conductance and complex impedance as the empirical data;
(B) deploying a test apparatus on the porous material under test, the test apparatus comprising one or more electrodes;
(C) providing one or more input electrical signals to the one or more electrodes, the one or more input electrical signals comprising at least one continuous radiofrequency signal;
(D) receiving one or more response signals from the one or more electrodes;
(E) comparing the one or more response signals to one or more empirically derived correlations for the type of the porous material under test;
(F) determining, from the comparison, one or more parameters of the porous material under test.
2. The method of claim 1 wherein the one or more parameters comprises a density of the porous material under test.
3. The method of claim 1 wherein the one or more parameters comprises a moisture content of the porous material under test.
4. The method of claim 1 comprising determining a capacitance and a conductance of the porous material under test.
5. The method of claim 4 comprising transforming the capacitance and conductance of the porous material under test into a density and moisture content of the porous material under test.
6. The method of claim 1 wherein deploying the test apparatus comprises deploying one or more flexible electrode sets onto the porous material under test.
7. The method of claim 1 wherein deploying the test apparatus comprises deploying one or more dart electrodes into the porous material under test.
8. The method of claim 7 wherein deploying the one or more dart electrodes comprises:
(A) disposing a dart template onto the porous material under test, the dart template indicating relative locations for a plurality of dart electrodes; and
(B) locating the plurality dart electrodes at the locations indicated by the template.
9. The method of claim 1 wherein connecting the test apparatus to the proctor mold comprises inserting a probe electrode into the material within the proctor mold.