GCR Moisture and Density (MAD) User Guide
Table of Contents
- 1 I. Introduction
- 2 II. Procedures
- 3 III. Data Review on LIMS From Previous Expeditions
- 4 IV. Important Notes
- 4.1 MAD Computations
- 5 V. Appendix
- 6 VI. Credits
- 7 VII. Archived Versions
Porosity definitions used on ODP Leg 161 [From Revil et al., 1997 (10.2973/odp.proc.sr.161.274.1999)]
I. Introduction
Core specimens for moisture and density (MAD) analysis are extruded from a section half for:
Mass: measured using a motion-compensating dual analytical balance system and a drying oven.
Volume: measured using a caliper or by a helium displacement pycnometer that employs Archimedes' principle of fluid displacement to determine the volume of solid objects.
The MAD properties of interest are:
Water content
Bulk density
Dry density
Porosity
Void ratio
These properties are calculated based on three out of four measured values:
Wet mass
Dry mass
Wet volume
Dry volume
Method Theory
Phase relationships of mineral density, porosity, void ratio, and water content are basic sediment and rock properties that are found most accurately through mass and volume determinations. The mass or volume of the bulk (wet) material, the dried material, and the extracted water (assumed to be interstitial pore fluid) is corrected for the mass and volume of salt evaporated during the drying process. The mass and volume of the evaporated pore water salts are calculated for standard seawater salinity, seawater density at laboratory conditions, and an average seawater salt density.
Soils can be either 2-phase or 3-phase compositions (i.e., completely dry or partially saturated). For MAD measurements the analyst determines whether the sample contains a 2- or 3-phase system:
Completely dry soil contains 2 phases: solid soil particles and pore air.
Fully saturated soil also contains 2 phases: solid soil particles and pore water.
Partially saturated soil contains 3 phases: solid soil particles, pore water, and pore air.
MAD data provide a direct estimate of porosity and void ratio and the average density of constituent minerals. Porosity variations are controlled by consolidation and lithification, composition, alteration, and deformation of the sediments or rocks. MAD data can be used to calibrate high-resolution gamma ray attenuation (GRA) bulk density data, which are sampled at a much higher resolution than is possible with the MAD method. If mineral density can be defined with sufficient precision, GRA bulk density can be expressed as porosity.
II. Procedures
A. Preparing the Instrument
MADMax is a C# application that controls all of the measurements used in the MAD process. It can be found on the applications web page. Due to browser compatibility issues, MADMax must be installed from Microsoft Internet Explorer; any other browser is unlikely to install properly.
Double-click the MADMax icon on the desktop (Figure 1) and login using ship credentials. MADMax main screen will open (Figure 2).
NOTE: If the user cannot login, please see a technician to ensure that the appropriate database authorization has been granted to the user account.
Figure 1. MADMax Icon.
2. The main screen of the application (Figure 2) is the central command center for the entire process. Various actions on this screen initiate the balance measurements, the pycnometer measurements, the entry of caliper data, and the calculation of the derived MAD results.
Figure 2. MADMax main screen. Note the pycnometer display screens below the main application window.
NOTE: It is possible to click the "Display ON" button to turn the live pycnometer monitoring off unless troubleshooting a problem. The live display is memory-intensive and will slow down the functioning of the software.
Once a sample has been assigned to a MAD vial using the Sample Master program, it will be available to the MADMax application. Click the "Refresh Sample List" button to cause the sample to appear in the table.
IMPORTANT! Note that once the samples are in the MAD vials, they are tracked solely by their container number. Care should be taken not to confuse the samples at any point in the process.
3. The main screen spreadsheet can be sorted by clicking on the column header, such as "Container". This will put all samples in order by container number.
B. Instrument Calibration
Calibration of the Pycnometer Cells
Before any pycnometer measurements can be made, the pycnometer cells must be calibrated. On the main screen, click the "Calibrate Pycnometer" button on the right side of the main screen in order to invoke the calibration window as shown in Figure 3.
Figure 3. Calibrating the pycnometer cells.
First select the standard to be used in the calibration. For the 35 cm3 inserts (Wheaton vials and aluminum cups), the best results are obtained by using "SPHERE_10," which is actually a 3 cm3 and 7 cm3 standard used together. Once the standard is selected (again, the normal standard used is "SPHERE_10"), assign it to a pycnometer cell using the pull-down selector as shown in Figure 4. Use at least 3 repetitions for good precision between measurements. Select SPHERE_10(1) and assign to Cell 1, SPHERE_10(2) assign to Cell 2, and so on.
Figure 4. Selecting the standard and then assigning it to the cell.
Click "Calibrate" once the standard and the cell have been assigned and the number of replicates is chosen. A window will appear for the cell that was chosen as shown in Figure 5. The first calibration step is to measure the empty cell. Ensure that the cell is empty before clicking "Done". The measurement will start immediately. If calibrating multiple cells, click on Calibrate Pycnometer again to set up and start the next cell, all six can run simultaneously and at different steps in the measurement cycle. You will end up with 6 measurement windows on the screen.
Figure 5. Cell 1 calibration window.
The pycnometer will step through its full measurement cycle once for each of the replicates selected (so three times if "3" was selected) as shown in Figure 6.
Figure 6. Pycnometer analysis steps.
The steps are detailed here:
The purge pulse and release step will repeat as many times as the number of replicates prior to moving on to the analytical steps below.
Purge (no.) Gas Pulse—fills the main chamber with helium
Purge (no.) Release Gas—empties the helium through both chambers
The following steps will repeat as many times as the number of replicates (without going back to the purge step).
Stabilize—allows the chambers to come to equilibrium with each other after the purge step.
Measure Atmospheric Pressure—measures the zero-point pressure in the analytical chamber (only).
Initial Pressure—opens the helium inlet to fill the analytical chamber.
Measure Initial Pressure—measures the initial pressure in the charged analytical chamber.
Measure Expansion Pressure—opens the expansion valve and then measures the equilibrated pressure in the analytical plus expansion chambers.
Exhaust Cell—releases the helium from both chambers.
Once the empty cell has been measured the specified number of times, the unit will prompt the user to add the standard(s) to the cell; the "SPHERE_10" standards are found in the wooden box shown in Figure 7. Open the pycnometer cell and place the standard ball(s) into the cell, then close securely. Clicking "Done" will trigger the above analytical steps, including purges, for the standard ball(s). After the replicate measurements on the steel ball(s) are done, the system will prompt the user to remove the standards from the cell. Pressing done at this point shows the expansion (red circle) and analytical cell (black circle) volumes determined by the calibration experiment as shown in Figure 8.
Figure 7. Six sets of steel balls are kept in this box along with the wire tool to extract them from the cells.
Note: Do not touch the spheres with bare fingers! Fingerprints don't significantly affect the volume measurement, but will cause the spheres to begin corroding. Wipe them thoroughly off with a Kim-Wipe if it is necessary to do so.
Figure 8. Final calibration screen for the pycnometer cell.
Click the "Accept" button (blue circle) to complete the calibration process for this cell. Once a cell's calibration is completed the pycnometer measurement on unknowns (i.e., samples) can be started independently of the other cells undergoing calibration.
To check the calibration, run the same set of standards as a sample. Double click on the spreadsheet in the green column (“Volume Dry”) for the cell and sphere you want to test. You may need to click “options” and select “include complete MAD tests” to display all samples. The Calculated volume should be between 10.098-10.302. Enter the value in the calibration excel spreadsheet on the desktop. The spreadsheet is conditionally formatted where if the standard volume is out of this range it will turn red. That means something is wrong and the cell needs to be calibrated again.
Always use the standards that are labeled for the corresponding cells. The standard containers are labeled 1-6 to match up will cells 1-6.
Frequency of Calibration/Calibration Check Standards
The pycnometer has proven to be quite stable, so the standard practice is to calibrate the instrument at the beginning of an expedition. To ensure quality, each set of five samples should be accompanied by a standard rotated through the cells. So long as the standards continue to give an acceptable value (less than 0.5% deviation), recalibration is not necessary (NOTE: As of X375 the recommendation is to Calibrate the beginning of each shift, and then +/- 0.5% deviation).
Rotation of the check standards through the cells is important, however, to ensure on a continuing basis that the system is still stable and functioning properly. An example measurement plan is given here:
Measure a sample in Cell 2, 3, 4, 5, and 6. Measure the 10.2 standard (3 cm3 + 7 cm3 balls) in Cell 1.
Measure a sample in Cell 1, 3, 4, 5, and 6. Measure the 10.2 standard in Cell 2.
Measure a sample in Cell 1, 2, 4, 5, and 6. Measure the 10.2 standard in Cell 3.
Measure a sample in Cell 1, 2, 3, 5, and 6. Measure the 10.2 standard in Cell 4.
Measure a sample in Cell 1, 2, 3, 4, and 6. Measure the 10.2 standard in Cell 5.
Measure a sample in Cell 1, 2, 3, 4, and 5. Measure the 10.2 standard in Cell 6.
Repeat pattern.
The SPHERE_10 standard fills the 35 cm3 chamber to the fullest degree and will give the best precision in measurements. Using a smaller standard will result in a larger headspace and a lower pressure drop, and therefore lower precision.
Use the air hose behind the pycnometer to clean out any dust and debris that gets in the cells. Check o-ring on the cell lids for any damage or dirt.
C. Set Measurement Parameters
Selecting the Appropriate Analysis Sub-method
The user needs to decide which sub-method (A, B, C, or D) should be used for the MAD analysis. The choice depends primarily on the type of sample material to be measured. In addition, Sub-methods A and B are not recommended from an analytical quality point of view. To choose between C and D based on the following criteria:
Saturation state of sample: | Saturated | Unsaturated | Soft, Saturated | Saturated |
MAD analysis sub-method: | C | D | A | B |
Is sub-method recommended?: | YES | YES | NO | NO |
MAD Measurement (LIMS Analysis) | ||||
Wet Volume (CALIPER) |
| X | X |
|
Wet Volume (PYC) |
|
|
| X |
Wet Mass (MAD_MASS) | X |
| X | X |
Dry Mass (MAD_MASS) | X | X | X | X |
Dry Volume (PYC) | X | X |
|
|
MAD Method C is the most common one used on the JOIDES Resolution. The MADMax application defaults to the "Method C" mode. The method indicator is a pull-down menu to switch between the four methods A, B, C, and D.
Regardless of method, the user can make up to five discrete types of measurements:
Depending on the method selected, different actions will be available by double-clicking on the color-coded section of the main screen appropriate to the method. For example, to make a wet mass measurement on a sample, double-click on the left-hand yellow cell as shown in Figure 9. This action will invoke the balance control software portion of MADMax.
Figure 9. Activating a wet mass measurement.
2. Order of Actions by Method
For each method, the measurements should be done in a specific order, as given below. Note that the MADMax interface does not sort these columns by this order, but the columns can be rearranged to do so if the user wishes.
In Method D's case, "wet volume" is better stated as "bulk volume," because the method is used only for samples with such high porosity that the water cannot be kept inside the sample (e.g., vesicular basalt or corals).
Figure 10 shows all of the methods and the required measurements for each one. Note that the colored columns for the measurements (yellow for balance, green for pycnometer, and blue for caliper) are slightly different for each method. The pink Methods Completed column is the same for each method and will be discussed later in the MAD Calculations section.
Figure10. All of the MADMax methods shown in cascade style.
D. Preparing Samples
Sediment Samples
Sampling Tools
For soft materials, syringes/plugs are used to extract sediment samples with a nominal volume of 10 cm3 from the section halves (Figures 11 a-b).
Figure 11a. Using cut-off syringe to get a 10ml sample. Figure 11b. Pushing sample out of syringe into assigned container, clean off debris around rim with a kim wipe.For hard materials, it is necessary to use drills and saws to cut cylindrical and rectangular prism-shaped rock samples; this is done in the core splitting room.
Sample Containers
Sample containers for the MAD analysis are either glass Wheaton vials or anodized aluminum cups (Figure 12). Each of them has a numeric identifier that is used to track the container and its sample throughout the process. Each container's mass and volume are recorded in the database and the MADMax program uses these values to subtract the container mass and volume from the sample values. Boxes of pre-weighed Wheaton vials are on the inventory list and must be checked out.
Wheaton type 800 vials are used for soft to indurated sediment samples; basically if it fits in the glass vial, use a glass vial. The glass vials have a density of 2.48-2.50 g/cm3 and their volume has been calculated from the mass determined on shore prior to shipment; their mass is approximately 21 grams and volume is about 8.3 cm3.
Anodized aluminum sample cups are used for igneous or consolidated sedimentary samples. The mass of each of the cups was determined experimentally (approximately 14.8 g) and the volume of 5.842 cm3 was estimated from the dimensions and confirmed by experiment.
Figure 12. Sampling tool (left), aluminum cup, and Wheaton vial for MAD measurements.
Hard Rock Saturation Method
Take a sample cube from the working section half, it is common to use the same size dimensions as a p-mag cube (or to share the same sample as long as scientists understand the measurement is destructive).
Hard rock samples do not require a vial and therefore use container ID “0” when entered.
Place the sample cube into a snap cap vial and fill until sample is covered with seawater.
All hard rock samples need to be saturated completely before running them through the MAD measurements. To do this, all samples will need to be placed in a vacuum for at least ~12hrs, preferably 24hrs.
To set up the vacuum, the vacuum bowl is filled with seawater before setting up the remaining components.
Connect the bowl to a vacuum hose that runs through the drain flask, this keeps any water getting to the pump. Place the stopper with the copper tubing in the top of the flask before directly connecting with tubing to the pump.
Once this is set up, the pump can be turned on to pressurize the vacuum bowl, it is recommended to run the pump intermittently during saturation, about 30 minutes at a time every 4 hours.
Once the samples have been under vacuum for the allotted time, they can be weighed for wet mass and placed in the oven to dry at 110C.
After 24 hours, the samples are then weighed for dry mass.
The hard rock sample can be placed directly into the pycnometer for measurement.
If the container ID was not entered as “0” in SampleMaster the User can add the container ID directly in MADMax by double clicking in the container cell that directly correlates with the desired sample.
E. Making a Measurement
Wet Mass Determination by Analytical Balance
As shown in Figure 9, above, double-click on the "Mass Wet (g)" column in the field adjacent to the sample to be analyzed. This will invoke the Balance Measurement dialog box as shown in Figure 13. The container number and the full Label ID of the sample will be displayed to ensure the correct sample was selected. Select the number of measurements to average (at least 300 is recommended, more if the sea state is high) and click "Measure." The measurement speed of the XS-204 balances is 5 Hz, so 300 measurements will take 60 seconds. The next screen will appear (Figure 14).
Figure 13. Balance Measurement dialog box. A typical expedition Label ID would be formatted as follows: 360-U1473A-21R-2-W 10/12-20127.
Taring the Balances
The first step to be taken is to tare the balances; measure the tare with empty pans. This step measures the differential tare between the two balances and is used to create a motion-compensated tare value. Do not try to tare the balances by using the Tare button on the keypad; the balances must be tared using the software. The window header will show the Text ID of the sample, what measurement is being done (e.g, "Mass Wet (g)"), and the container number.
Activate the tare function by clicking the "Tare" button on the upper left-hand corner of the screen (circled in green) and the tare will begin. The reference balance trace is green, the unknown balance trace is red, and the corrected mass (in this case the tare value) is a blue trace.
The balances should be tared relatively often as many things can affect the balance reading. The most common causes of these changes are:
Spilling something on the balance pan (and please don't leave it there!)
Cleaning something that was spilled on the balance pan
Temperature changes in the laboratory may affect the zero point of each balance
It is recommended that the user tare no less frequently than 6 hours, but certainly if the user suspects anything may have changed on either balance.
After a tare, check by placing a known weight (20g) on both balances and click "Weigh". The corrected value should read 20g. If not, take a new tare.
Figure 14. Taring the paired balances at 300 measurements.
Making the Measurement
Once the tare is complete, place the sample container on the unknown balance and close the sliding door. Place counterweights from the standard box as close to the mass of the unknown as possible and close the reference balance door. It may be useful to look at the balance LCD screens; the circle shows the rough load on the balance and masses can be roughly equalized by using them. It is important to get the masses within 5 grams. If the red and green traces are more than 5 grams apart after the measurement is started, then press the "Stop" button, add or subtract reference masses, and start the measurement over.
The "Reference Mass" field should be filled with the total mass of the reference masses before the measurement is started. Figure 15 shows the Reference Mass (circled in blue) and the traces of the two balances and their corrected result mass. Note that the reference mass balance began at a value of just under 19 grams and the unknown balance started close to 21 grams; the difference between them is ≤5 grams, so this measurement could be allowed to continue.
Figure 15. Mass measurement on a sample.
Once the analysis is completed (Figure 16), the mass determined by the measurement process will be displayed (in this case 22.120 grams). The "Tare" button is active again, but it not appropriate to use it at this time without removing the sample and reference masses. The user has three choices: accept the result and send it to the main screen display and the LIMS database by clicking the "Accept" button, reweigh the mass by clicking the "Weigh" button again, or completely cancel the measurement and discard all results by clicking the "Cancel" button.
The user should note that the instantaneous values of the balances varied by more than 20 grams in this example because of ship's heave, but the measured mass (22.110 grams of known masses) was accurate to within 0.010 grams.
Note: At the time of writing this manual, the Std Deviation field is recording the standard deviation of the unknown mass measurement (which obviously varies highly). An upcoming upgrade will switch this to the corrected mass value. Has been done?
Figure 16. Completed measurement.
Once the "Accept" button is pressed, the user is returned to the main MADMax screen.
Reassigning Results
The result should be in the appropriate field, but in case the user double-clicked the wrong mass measurement, MADMax provides the capability to switch the mass measurement from "wet" to "dry" and vice-versa. As shown in Figure 17, right-click the mass cell and select the "Swap the result with Mass Dry (g)" option. If two masses are already present, this option will instead state "Swap Mass Dry (g) and Mass Wet (g)" to swap the mass measurements.
Figure 17. Right-click options for the mass measurement.
Once the user clicks the "Swap" options, a window will pop up to confirm the action as shown in Figure 18; the window for moving a result from wet-to-dry or dry-to-wet is very similar.
Figure 18. Reassign Result window. It is important to be able to do this as the drying
step is irreversible and the wet mass cannot be repeated without taking a new sample.
Cancel Mass Result
The user can also cancel a result using the same right-click option, with a confirmation window as shown in Figure 19. A technician can uncancel the result if this was done in error.
Figure 19. Cancel mass result pop-up window.
Review Results
If the user wishes, they can also look at the details of the mass results as shown in Figure 20. This is a summary of all of the parameters used to determine both the wet and dry masses with the parameters labeled by their database names.
Figure 20. Review wet mass results window.
The mass_dry and mass_wet components are the mass of the sample. The mass_dry_container and mass_wet_container components are the mass of the sample and the container together.
Dry Mass Determination by Analytical Balance
Put samples in the oven, uncovered, for at least 24 hours at 105°C . Let them cool to room temperature in the dessicator boxes for about 3 hours before placing inside pycnometer cells.
This step is performed the same way as the wet mass determination. Double-click on the "Mass Dry (g)" column in the field adjacent to the sample to be analyzed. Follow the rest of the instructions in Wet Mass Determination by Analytical Balance, except that it applies to the dry mass measurement.
Dry Volume Determination by Helium Pycnometer
Making a Pycnometer Measurement on a Sample
After calibration is complete, the user can begin analyzing samples and one standard per six runs as noted above. Double-click on the Volume Dry (cm3) portion of the main screen next to the sample to be studied; normally the SPHERE_10 standards are also listed for the one cell in six to be dedicated for a standard measurement. A window will appear as shown in Figure 21 prompting the user to select a cell and to set the number of replicates. It is recommended to use the same number of replicates as the calibration.
Figure 21. Pycnometer measurement window.
Important! Ensure that the sample is correct and select the cell to be used and the number of replicate measurements to be performed.
Once the user has selected the cell and number of cycles, click the "Measure" button, which will open the pycnometer cell control window (Figure 22). Place the sample container in the cell using long tweezers and do not put the cap on the container (Figure 23). Screw the lid back on the cell and then click "Done" followed by clicking the "Start" button (circled in blue). Unlike the calibration measurement, the experiment will not start until the "Start" button is clicked.
Figure 22. Starting a pycnometer measurement on a sample.
Figure 23. Loading the sample container into the cell.
The pycnometer will step through the same purge and measurement steps described in the calibration section and when it is finished, will show the screen shown in Figure 24.
Figure 24. Sample completed indicator for pycnometer.
Once the "Done" button is clicked, the volume of the sample (including the volume of the container) will appear in the "Calculated Volume" window. At this point, the user may select "Rerun," which will redo the measurement, "Cancel" to reject the measurement, or "Accept" to keep the data and transfer it to the main screen.
Making a measurement on a mini-core sample
A special aluminum insert (Figure 25), as pictured below on the right, was made to accommodate longer samples that will not fit into the normal insert. It is located in a labeled zip-lock in the pycnometer drawer in the lab. The procedures and calibration are exactly the same as with the normal inserts. When swapping to this insert run a calibration right away with the standard that corresponds to the cell used, and run the standard as a control sample every sixth measurement. When swapping back to the regular insert make sure to calibrate it again before using.
Figure 25. Mini-core aluminum insert.
Reassigning Results
The result should be in the appropriate field, but in case the user double-clicked the wrong volume measurement, MADMax provides the capability to switch the volume measurement from "wet" to "dry" and vice-versa. As shown in Figure 26, right-click the mass cell and select the "Send this result to the Volume Wet (cm3)" option. If two volumes are already present, this option will instead state "Swap Volume Wet (cm3) to Volume Dry (cm3)."
Figure 26 Right-click options for the volume measurement.
Once the user clicks the "Swap" options, a window will pop up to confirm the action, similar to that for the swap mass measurements window.
Cancel Volume Result
The user can also cancel a result using the same right-click option, with a confirmation window similar to the one for canceling mass measurements mentioned earlier. A technician can uncancel the result if this was done in error.
Review Results
If the user wishes, they can also look at a detail of the mass results as shown in Figure 27. This is a summary of all of the parameters used to determine the volume with the parameters labeled by their database names.
Figure 27. Review dry volume results window.
The volume_dry component is the volume of the sample. The volume_dry_container component is the volume of the sample and the container together. The pyc_stdev value is calculated from the individual measurements (in this case, three) done by the pycnometer.
Volume Determination by Caliper
Volume determination by caliper is best used on consolidated, high-porosity samples (e.g., coral or vesicular basalt) as part of Method D. It is not likely to give accurate results when used on soft sediments (Method A).
Double-click on the "Caliper Volume (cm3)" column in the field adjacent to the sample to be analyzed. This will invoke the caliper measurement window as shown in Figure 28. The user should select cube or cylinder depending on the sample to be measured with the precision caliper.
Figure 28. Caliper measurement entry screens.
Ensure that the sample being measured is the correct one and click either the "Cube" or "Cylinder" radio button. Make the measurements using the precision caliper (Figure 29). Enter the measurements for each dimension in centimeters. Once the measurements have been entered, click "Ok" and the result will be transferred to the main screen.
Figure 29. Digital caliper used for volume measurements.
Review Results
Right-clicking the caliper result will allow the user to select "Review Results" to see details of the measurement.
Cancel Result
The right-click window also gives the user the ability to cancel the result. A developer or technician can uncancel the result if this was done in error.
Wet Volume Determination by Helium Pycnometer
NOTE: This method (part of MAD Method B) is not recommended as water vapor will be produced from the wet sample and negatively affect the data quality!
However, if the user wishes to perform this analysis, use the same guidelines as found in Dry Volume Determination by Helium Pycnometer, above.
MAD Calculations
The MADMax software will calculate all of the other MAD parameters once any three of four measurements are completed: wet mass, dry mass, dry volume, and wet volume. Once the three measurements related to the chosen method (e.g., Method C: wet mass, dry mass, dry volume) are completed, double-click on the "Methods Completed" field on the line of the sample in question. This will invoke the MAD calculation window as shown in Figure 30.
Figure 30. Run MAD Calc window. Ensure the proper sample is shown.
Click on the "Run MAD Calc" button and after a brief pause, the calculated parameters for the MAD analysis will appear on the main screen for that specific sample and will be updated in the LIMS database at the same time. See the "MAD Computations" section below for more information about the various parameters determined by the software.
Reviewed by Nicolette 6 August 2018