Steel spacers can be placed under cores and pavement slabs if needed. The container with the specimen is then placed into the wheel-tracking device. The most commonly used test temperature in Hamburg is 50 o C, although 40 o C has been used when testing certain base mixtures. A water temperature of 50 o C is reached within 45 min. Specimens are conditioned at the test temperature for a minimum of 30 min.
Heat is provided by heated coils in the water.
The temperature of the water is then maintained by these heating coils and by introducing cold water from a faucet. The device tests two slabs simultaneously using two reciprocating solid steel wheels. The wheels have a diameter of 203.5 mm and a width of 47.0 mm. The load is fixed at 685 N and the average contact stress given by the manufacturer is 0.73 MPa. This assumes an average contact area of 970 m2, which is based on the 47.0-mm wheel width and an average contact length of 20.6 mm in the direction of travel.