Accelerated full scale testing of low cost heavy duty pavements: experience with the accelerated loading facility (alf)

The accelerated loading facility has completed more than 4.2X10**6 loading cycles up to date, and provides valuable information on the pavement performance under accelerated loading. Once the initial mechanical problems had been overcome, the alf applied an average of 35,000 load cycles per week. Three pavement types were tested, each typical of the current design and construction practice of heavy duty pavements of the host state road authority. The pavement performance and structural response were monitored by means of surface and subsurface deflections, permanent deformations, in depth strains and visual observation of surface deterioration. A method for assessing critical strains based on the measured surface deflection bowls and in depth deflections was developed, which makes it possible to continuously monitor (and analyse) the structural performance of the tested pavements. Cross reference between analytical approaches based on the equivalent layer thicknesses and on the surface curvature index yielded consistent results, increasing confidence in both approaches. The first two trials proved the adopted design and construction practices to be adequate by indicating long pavement lives. The experiment on the cement treated base pavements underlined the significance of the bond between base layers as the lack of such a bond may cause premature failure despite the strength of the applied materials or structure (a).