Virginia
FHWA Accelerated Loading Facility
The Accelerated Loading Facility (ALF) is a transportable linear full-scale accelerated loading facility which applies a rolling wheel load on a 13.7 m (45 ft) test length of any test pavement. The picture below shows two ALF machines at the Pavement Testing Facility (PTF) by the Federal Highway Administration (FHWA). The first ALF was delivered to PTF in 1986 and the second was purchased in 1993.
The ALFs simulate traffic at controlled loading and pavement temperature conditions. An infrared heating system and thermocouples in the pavements provide the required pavement temperature. The ALF frame is 29 meters long (95 ft) and about lane-width (3.6 m or 12 ft). Each machine is capable of applying an average of 35,000 wheel passes per week from a half-axle load ranging from 33 kN (7,500 lbf) to 84 kN (19,000 lbf). An electric motor provides unidirectional loading passes at constant speed programmable up to 18 km/h (11 mi/h).
Radiant heaters are used to maintain an ambient temperature control; temperatures as high at 74 °C (165 °F) can be generated to accelerate asphalt rutting and during the fall, spring, and winter. Lateral wheel wander of the ALF transverse position is programmable. Three standard deviation tables are available: zero wander, 50 mm (1.74 inches) and 133 mm (5.25 inches) standard deviation.
Virginia Smart Roads
The Virginia Smart Roads is a 5.7-mile, limited-access highway of which the first 2 miles is designated as a controlled pavement test facility. The road has two lanes in each direction, and a 3.0m shoulder on each side. Provisions exist to route traffic around controlled test zones to allow for ongoing testing. The pavement research plan provides for testing of various hypotheses on pavement material performance and characteristics, all pavement layers are instrumented for monitoring loading and the environment. The simulation of different types of weather conditions is possible. An underground conduit network provides on-site data acquisition
The pavement test road includes 12 flexible pavement test sections and a continuously reinforced rigid pavement. The sensor array includes strain gages, pressure cells, thermocouples, time-domain reflectometry (TDR) probes, and resistivity probes. Some unique measurements in this facility include measuring strain in the aggregate layer, pressure underneath the hot-mix asphalt (HMA) layer and direct measurements of moisture.
