Material properties needed for pavement design are elasticity, susceptibility to permanent deformation and durability. Elasticity is at present determined by repeated triaxial tests, but susceptibility to permanent deformation is very difficult to assess because stresses induced by moving wheel cannot be reproduced in tests. Durability is estimated by simple laboratory tests. A Pavement Test Facility has been developed. Structure to be tested is produced in a 1200x900x600 mm test box and unidirectional or bidirectional loads of 7-25 kN can be imposed by a moving wheel. Load speed is 5 km/h. Temperature in the test chamber can be set at +5 - +60 degrees C. Elastic and permanent deflections are measured by LVDTs connected to steel rods and placed at any required point in test structure. Strains can be determined from these deflections. Pressure cells can also be used; horizontal tensile strains at the bottom of the bound layer can be assessed using strain gauges, and fatigue can be determined from stiffness and deformation data. Results of tests show that the facility functions satisfactorily.
Samenvatting