Toward Developing a Rational Quality Assurance Program for Flexible Pavement Construction

Under end-result specifications for HMA pavement construction the contractor takes full responsibility for constructing the pavement to the specified quality. This requires that the quality assurance (QA) tests performed by the highway agency for acceptance should be good indicators of expected performance. Lack of established relationships between QA tests and performance gets even more compounded by the fact that different mix and construction characteristics affect each other’s influence on performance. Mechanistic-Empirical Pavement Design Guide (M-E PDG) is an excellent tool to study the individual as well as their combined effect on performance and therefore can be used to develop rational QA program based on expected performance rather than subjective engineering judgment. To this end first 11 of the input variables with most significant influence on performance were short-listed by a thorough analysis of all the input variables required by the HMA module of the M-E PDG software. A two-level full factorial experiment was designed and run to assess their main and interaction effects on rutting and fatigue cracking performance. Response surface interpolation was further used to determine the expected difference in service life because of deviation from the target quality. Knowledge of expected loss in life was used to determine specification limits for asphalt concrete layer thickness, in-situ air voids and effective binder content for an HMA pavement QA program. It was observed that fatigue performance is more critical than rutting performance and also that many times appreciable loss in service life may have to be accepted because tighter specifications to reduce loss in life may not be practically achievable in the field. The strategy demonstrated in this paper can be used for other quality characteristics for HMA as well as rigid pavements.