Twenty-Year Performance Review of Asphalt Concrete Long-LifePavements with Performance-Related Specifications

The first asphalt concrete long-life (AC Long Life) project was constructed in Los Angeles County on Route 710 (LA-710) near Long Beach in 2001/2004 and is now over 20 years old. Four more AC Long Life projects have been completed in California since then, three between 2011 and 2014 (TEH-5, SIS-5, SOL-5), and one in 2021/2022 (SAC-5). The goal of these AC Long Life projects was to achieve design lives of 30 years or 40 years (the standard Caltrans asphalt pavement design life was 20 years at the time). Measures taken to achieve those lives included the use of performance-related specifications for job mix formula approvals, higher compaction requirements, and the use of a three-layer asphalt concrete system for structural capacity. These measures required additional costs. Calculations indicate that the longer lives will result in life cycle cost reductions if they achieve the design lives. Hence, periodic performance evaluations are important, which is the purpose of this technical memorandum. Extensive material sampling and structural evaluation were conducted regularly on the LA-710 and TEH-5projects. This technical memorandum reviews the available performance data, summarizes the material testing and structural evaluation data for the LA-710 and TEH-5 projects, and compares the as-built materials with statewide medians. The cracking, patching, roughness (IRI), and rutting data revealed that these projects had all performed very well in general at respective 10- to 20-year milestones. No rehabilitation and only one minor maintenance activity has been performed on LA-710, and no maintenance/rehabilitation activity has been performed on the 10-year-old projects. Analysis of the LA-710 and TEH-5 deflection data suggests some densification (not to the extent of crushing) and aging in the asphalt-bound layers but no signs of traffic-induced damage. Laboratory test data on between-wheelpath specimens from the TEH-5 project indicate that the as-built materials in general have better fatigue performance, lower stiffness, and lower permanent deformation performance than the statewide median materials tested during mix design. Given the fact that only minor rutting has been observed in these projects, the as-built materials are believed to be good examples of mixes with balanced performance, with a few exceptions.