The pavement is built in an annular concrete tank 4m wide by 1.5m deep. The tank has a mean radius of 9.2m and a volume of 400m3. The tank means that the moisture content of the pavement can be controlled, regardless of the level of the water table at the site.
The subgrade material is placed by a loader, compacted with a small sheepsfoot trench roller then trimmed to shape. The subgrade is often 1.2–1.3m deep and has a California bearing ratio (CBR) set by the projects requirements between 1–14%. Clay is typically used for the subgrade as the strength can be controlled by varying the water content.
The sub-base and basecourse materials are either placed by a paver or can be levelled using a laser controlled blade mounted on a tractor. It is then compacted with a large plate compactor and combination roller to the project's requirements.
Either a chipseal or an asphaltic concrete surfacing is used. The chipseal binder is sprayed with a custombuilt spray bar and the asphaltic concrete surfacing is laid with a standard paving machine.
3D inductive soil strain coils, asphalt H bar strain gauges, soil pressure cells, time domain reflectometry moisture gauges, temperature and soil suction gauges are available to be installed in the pavement during construction.
In addition to laboratory materials testing, extensive use is made of nuclear density measurement, static and dynamic cone penetration testing, and falling weight deflectometer (FWD) equipment to monitor the quality of the pavement during construction.
The simulated loading and vehicle emulator (SLAVE) units can rotate at 20,000 revolutions in a 24–hour period, meaning that the equivalent of 15–20 years' worth of traffic can be applied in 6–9 months. Insitu instruments regularly measure strain, stress, moisture, suction and temperature. The functional performance of the test is measured at defined intervals in terms of rutting, roughness, texture, stiffness and dynamic load changes.
At the completion of the accelerated loading phase of a project, the pavement is trenched and tested to help understand mechanisms and the extent of any failures and/or types of distress present.
