Operating Instructions for the Gilson MD-2000 Micro-Deval Apparatus

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This manual is a guide to the operation and maintenance of the Gilson MD-2000, MD-2000C or MD-2000F Micro-Deval Apparatus. This unit has been designed and manufactured to comply with current published specification requirements.

The operator is referred to the most current revisions of ASTM, AASHTO or other governing specifications for testing methods and procedures.

The Micro-Deval Apparatus meets or exceeds the accuracy and repeatability requirements of the “Standard Test Method for Resistance of Coarse Aggregates to Degradation in the Micro-Deval Apparatus” AASHTO Designation T 327, ASTM D 6928, TexDot 845-49-40, and Ontario LS-618. As well as the “Standard Test Method for Resistance of Fine Aggregates to Degradation in the Micro-Deval Apparatus, ASTM Designation D 7428 and Ontario LS-619.

The MD-2000 Apparatus is supplied with two stainless steel jars, stainless steel abrasive charges and a magnetic pickup. A prepared aggregate specimen is placed in the abrasion jar along with an abrasive charge of stainless steel balls and water. The sealed jar is then placed on a set of rollers and turned for a period of time. At test completion, the aggregate sample is removed from the jar and tested to determine degradation resulting from abrasion.

The MD-2000 controller functions as both a timer and a jar revolution counter. Duration of the test may be controlled by either method. Most current specifications call for the test to be based on elapsed time at a specified speed. It has been demonstrated that controlling the test by counting jar revolutions via an optical encoder results in more consistent sample agitation. In TIME mode, operation terminates when the timer counts down to zero from the time input by the operator. In REVS (Revolution Counter) mode, the user inputs the desired number of revolutions into the counter. Revolutions are then tracked via an optical encoder until
they reach zero, at which point the unit will stop.

To perform a test with the MD-2000, first refer to the test protocol in the governing specifications and prepare the aggregate specimen as specified.

1. Load the prepared sample into the abrasion jar along with the specified amounts of abrasive charge (stainless steel balls) and water.
2. Carefully clean and dry off the rim of the jar and the lid gasket.
3. Place the lid on the jar and secure with the threaded locking knob.
4. Invert the jar and check for leaks.
5. Place the jar on its side on the roller set with the clamping end facing the optical encoder.
6. Check that timer or revolutions mode is selected properly and that settings are correct. If necessary, input new settings as noted in previous section.
7. Check that there are no foreign objects or obstructions in the jar chambers.
8. Close and secure the cabinet doors; first the bottom then the top, latching door.
9. Press the green START button. Depending on the mode selected, the timer or the revolutions counter will then control the duration of the test and stop the machine automatically at completion.

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