Statistical Assessment of Quality Control Data for Hot Mix Asphalt

Recent trends in the paving industry have resulted in increased contractor involvement in the design, acceptance, and performance of hot mix asphalt (HMA) pavements. As a result, questions have arisen about whether contractor process control tests, alternatively known as quality control (QC), should be incorporated into the acceptance and pay factor processes that state highway agencies currently use. To examine this issue, various statistical tests were used including F and t-tests to compare QC data to agency-obtained quality assurance (QA) results. The percentage of projects that exhibited statistically significant differences in mean values and variances was calculated and assessed. For projects that had statistically similar QC and QA results, the average difference between the two testing programs was calculated. The results of the statistical analysis were analyzed from both a statistical and engineering perspective.

This report contains data from four state DOTs—California, Minnesota, Texas, and Washington. These states also provided the funding for the study.
Publication Date: 
Sunday, February 1, 2009
Publication Number: 
WA-RD 686.1
Last modified: 
10/12/2016 - 15:41
Colin J. LaVassar, Joe P. Mahoney, and Kim A. Willoughby.
Washington State Transportation Center (TRAC)
Number of Pages: 
Paving, Contractors, State departments of transportation, Hot mix paving mixtures, Quality control, Quality assurance, Statistical analysis, Analysis of variance, T test, Precision, Bias (Statistics).