Mechanistic-Empirical design of perpetual pavement

Abstract

Perpetual pavements use multiple, durable asphalt layers to produce a safe, smooth, long-lasting road. The pavement design begins with a strong, yet flexible bottom layer that resists tensile strain caused by traffic, and thus stops cracks from forming at the bottom of the pavement. Four perpetual pavement sections were designed and constructed in 2005 and currently are scheduled for rehabilitation for top-down surface cracking. These cracks have been confirmed by full-depth cores. This study revisited the design of these perpetual pavement sections using now available PerRoad and AASHTOWare Pavement ME Design software to investigate whether the design assumptions were correct. Fatigue lives of these sections were also evaluated based on bottom-up cracking. Layer moduli were backcalculated from the falling weight deflectometer (FWD) deflection data using the EVERCALC software. Tensile strains at the bottom of the asphalt layer were then computed. Results showed that predicted strain values derived from the mechanistic response models were lower than the tensile strains computed using moduli from the FWD deflection data. The required asphalt thickness from PerRoad was relatively higher than the asphalt thickness obtained from the AASHTOWare Pavement ME Design software over a 50-year design period. The study identified the most successful perpetual pavement design as the one with a rich bituminous mix in the base layer.