The Perpetual Pavement concept was first articulated in 2000 and the concept has rapidly gained acceptance.
The APA’s newest technical document on the subject is Perpetual Asphalt Pavements: A Synthesis. This comprehensive publication captures the activities that have taken place over the last decade, synthesizes the information in way that is useful to providing guidance for Perpetual Pavement design and construction, and provides a vision for further research and development to refine Perpetual Pavements.
Perpetual Pavement Design Software
The APA offers two versions of its software for the design and analysis of Perpetual Pavements. Both versions of the software are available as free downloads.
PerRoad uses the mechanistic-empirical design philosophy. The program couples layered elastic analysis with a statistical analysis procedure (Monte Carlo simulation) to estimate stresses and strains within a pavement. Version 4.4 provides design results as percentile responses and as conventional designs with transfer functions. In order to predict strains that would prove detrimental for fatigue cracking or structural rutting, PerRoad requires the following inputs:
- Seasonal pavement moduli and annual coefficient of variation (COV)
- Seasonal resilient moduli of unbound materials and annual COV
- Thickness of bound materials and COV
- Thickness of unbound materials
- Load spectra for traffic
- Location for pavement response analysis
- Magnitude of limiting pavement responses
- Transfer functions for pavement responses exceeding the user-specified level for accumulating damage
PerRoadXpress is an easy-to-use, all-on-one-screen program for designing Perpetual Pavements for low- and medium-volume roads and parking lots. The designer chooses a type of asphalt cement. PerRoadXpress then allows the designer either to use defaults for traffic and soil, or to input the actual values if they are known. Granular base thicknesses from 0 to 10 inches are included. The software quickly provides the user with a recommendation for the total thickness of asphalt pavement needed for a particular situation. PerRoadXpress was developed in response to requests by public works officials and owners of commercial property.