Statement_of_Work_Hamburg.docx

Statement of Work

This statement of work is for the purchase Hamburg Wheel-Tracking Device (HWDT) in accordance with AASHTO T-324 “Hamburg Wheel-Track Testing of Compacted Asphalt Mixtures”. The HWDT is used to determine the premature failure susceptibility of asphalt mixture due to weakness in the aggregate structure, inadequate binder stiffness, or moisture damage. The test method measures the rut depth and number of passes to failure. It is applicable to hot mix asphalt testing and is a method of measuring rutting depth as well as moisture susceptibility.

Specification/Requirements

A. Electro-Mechanical Hamburg Wheel-Tracking Device Design

1. Comply with all AASHTO T-324 requirements.

2. An electrically powered machine capable of moving a 203.2 ± 2.0-mm (8 ± 0.08-in.) diameter, 47-mm (1.85-in.) wide steel wheel over the center (x and y axes) of the test specimen.

3. The load on the wheel is 705 ± 4.5 N (158 ± 1.0 lb).

4. The wheel reciprocates over the specimen, with the position varying sinusoidally over time.

5. The wheel makes 52 ± 2 passes across the specimen per minute. The maximum speed of the wheel, reached at the midpoint of the specimen, is approximately 0.305 m/s (1 ft/s).

6. Device shall have capability to test specimens wet or dry and allow specimen submersion centered along the wheel path in water bath capable of controlling the temperature within ±1.0°C (1.8°F) over a range of 25 to 70°C (77 to 158°F) with a mechanical circulating system stabilizing the temperature within the specimen tank.

7. A linear variable differential transducer (LVDT) device capable of measuring the depth of the impression (rut) of the wheel at the center ±1/2 in. along the length of the wheel’s path, to within 0.15 mm (0.006 in.), over a minimum range of 0 to 20 mm (0 to 0.8 in.). The system measures the rut depth, without stopping the wheel, at least every 400 passes. Rut depth is expressed as a function of the wheel passes.

8. A non-contacting solenoid that counts each wheel pass over the specimen. The signal from this counter is coupled to the wheel impression measurement, allowing for the rut depth to be expressed as a function of the wheel passes.

9. Maximum overall floor space footprint of 49 inches x 55 inches.

10. Programmable to allow various rut depths and/or different temperatures.

11. Data acquisition of measurements from USB port and Printer.

12. Automatic Parking of compaction wheels that require no lifting.

13. Can operate on 208/220/230/240 Volt system.

14. Slide in place sample placement to allow ease of loading.

15. Maintenance of equipment must be able to be accomplished by laboratory technician.

16. HWDT must have capability of performing wet and dry samples in one operation.

B: Specimen Mounting System

1. Comply with all AASHTO T-324 requirements for Specimen Mounting.

2. Slab Specimen Mounting System—A stainless steel tray that is mounted rigidly to the machine. The mounting system must restrict shifting of the specimen to within 0.5 mm (0.02 in.) during testing and must suspend the specimen to provide a minimum of 20 mm (0.8 in.) of free circulating water on all sides.

3. Cylindrical Specimen Mounting System—An assembly consisting of two high-density polyethylene (HDPE) molds or plaster of paris, conforming to Section 8 to secure the specimen (as shown in Figures 1 and 2), placed in a stainless steel tray that is mounted rigidly to the machine. This mounting system must restrict shifting of the specimen to within 0.5 mm (0.02 in.) during testing and must suspend the specimen to provide a minimum of 20 mm (0.8 in.) of free circulating water on all sides.

C: Calibration/Verification Equipment

1. Verify the LVDT calibration in accordance with ASTM D6027.

2. Verify the load from the wheel loading assembly at the level position to be 705 ± 4.5 N (158 ± 1.0 lb).

3. Verify that the wheel is reciprocating on the test sample at 52 ± 2 passes per minute.

4. Verify sinusoidal wave loading.

D: Safety Features

1. HWTD Must have enclosure which locks upon operation and does not allow access to moving parts.

E: Software Design

1. Must collect Rut Depth with each number of passes in format easily transferrable to csv file extension for use in common products such as Microsoft excel.

2. Must have programmable temperature control which can accept an offset to the sensor to ensure recorded temperature is within ±1.0°C (1.8°F) of actual measured temperature.

F: Service & Support

1. The Hamburg Wheel Tracking Device supplier must be capable of support through phone, e-mail, and network with Ethernet connection.

2. Must offer an on-site assistance in installation and training to properly perform AASHTO T 324.