Resilient modulus testing of unbound materials: LTPP's learning experience

Resilient modulus is a key data element for characterizing unbound pavement materials within the LTPP program. Although the test has been around for nearly three decades, its implementation within the program has been a challenge. A suitable test protocol was not available when the program began in 1987. It was incorrectly assumed in the early years that equipment manufactured for the test would work as intended. It was also incorrectly assumed that properly operating equipment and knowledgeable personnel imply good data. This paper has been prepared to share LTPP's experience over the past 14 years in achieving repeatable, high-quality resilient modulus data. Specific issues addressed in the paper include the test protocol, laboratory startup and quality control procedures, quality control and quality assurance processes, and comprehensive guidelines contained in an easy-to-use, interactive CD-ROM.