Variability of in-situ HMA volumetric and mechanistic characteristics using non-destructive test (NDT): case study

Abstract

This paper discusses the variability of in-situ physical and mechanistic characteristics of three construction projects using non-destructive test (NDT). Six sites from each project in the state of Louisiana were selected. Three NDT tests – falling weight deflectometer (FWD), light falling weight deflectometer (LFWD) and pavement quality indicator (PQI) – were carried out during and after construction. The deflection data from FWD and LFWD were utilised to backcalculate in-situ layer moduli and composite moduli, respectively. ELMOD and MICHBACK backcalculation softwares were used to calculate and compare the hot mix asphalt (HMA) layer moduli. The in-situ density of the HMA layer was obtained from the PQI device. Project variability in the in-situ measurements of the HMA layer was attributed to HMA layer thickness, temperature and seasonal variations. It was found that there was a good relationship between the HMA composite moduli calculated using the FWD deflection and Bossinesq's equation and moduli from the LFWD. The results also indicated that there was no strong relationship between the in-situ moduli and in-situ PQI voids.

Keywords:

• non-destructive tests
• backcalculation
• falling weight deflectometer
• light falling weight deflectometer
• pavement quality indicator
• variability

Acknowledgements

The authors wish to express their sincere thanks to the Louisiana Transportation Research Center (LTRC) for their financial support. Special thanks are also extended to LTRC and LADOTD researchers, project engineers and field staff for their support and valuable inputs in data collection.