Volume 33, Issue 4 (July 2005)
Analysis of Variability in Pay Factor Systems and Sampling Methods
Many state departments of transportation (DOTs) have incorporated a pay factor system into their quality assurance/quality control (QA/QC) programs. Currently, there is no standard sampling method for QA/QC programs nor for pay factor systems. This paper examines dissimilar types of sampling processes and their effects on pay factors along with different pay factor methods. The results can aid in establishing a pay factor system and selecting an appropriate sampling method based on the volumetric characteristics and a chosen type of pay factor system. A pay factor system based on sample means and a pay factor system based on risk analysis of hot mix asphalt (HMA) quality characteristics were examined. Hot mix asphalt mixtures standard in Michigan were used for the case study, along with five Michigan Department of Transportation (MDOT) sampling methods. The final analysis indicated that using a measured asphalt binder content probability-based pay factor system sampled via a Plate and Shovel method was the most precise system. Using a consistent sampling method ensures that pay factor systems are fair. A sampling method that is consistent in measuring results will be beneficial to contractors and owner/agencies by making payment based on HMA qualities that are representative.