Laboratory wheel tracking apparatus for bituminous pavement studies

Abstract

Rutting deformation is one of the most common forms of pavement distress found on bituminous pavements, especially in the hot, tropical climate of Singapore. These deformations are usually found in the wheel track on roads carrying heavy, slow moving, channeled traffic, such as in the city and industrial areas at traffic light junctions. To aid our investigation into the nature of pavement rutting, a laboratory wheel-tracking apparatus was used to simulate channeled wheel traffic loading under controlled conditions. It was upgraded with automated temperature and rut profile measurement capability. This article describes the features of the apparatus, which include temperature control of test specimens from ambient (27°C) to 70°C via a water bath with an adjustable weir, speed control of 0 to 80 wheel passes per minute, and variable wheel loading from 18 to 54 kg giving approximate equivalent tire pressures of 175 to 530 kPa. The apparatus can be used to simultaneously test three standard specimens of dimensions 405 mm by 135 mm by 90 mm-thickness. Single tests of two other sizes, which are two or three times the width of the standard specimen, are permissible. The rut depths are monitored by means of three linear variable displacement transducers (LVDTs), which measure the vertical displacements of each of the three wheel axles independently as rutting progresses. Due to errors induced by machine vibrations, accurate rut profile measurements can be made only under static conditions at selected intervals of wheel passes. With the use of a 200-ton-capacity static press, uniform dense asphaltic concrete beam specimens can be made, giving reasonably repeatable rutting test data on the apparatus, thus making it a valuable tool for evaluating the rutting potential of various mixes.