Contractor Quality Control Testing Levels For Highway Construction

Constructing a quality highway facility is a primary objective of state highway agencies (agencies) and contractors. Over the past several years, agencies have been working with the construction industry to implement Quality Control / Quality Assurance (QC/QA) specifications in an effort to enhance the quality of highway construction. With these new specifications come new responsibilities and challenges for the construction industry to ensure that design targets are achieved and that product variation is minimized. Contractors need efficient methods to understand where variation sources exist during various highway construction processes, particularly during material production and placement. Standard control charts are widely used by many highway contractors to control variation during construction, however, they lack the ability to isolate particular sources of overall product variation. This paper presents analysis of variance (ANOVA) statistical models to measure and understand sources of highway construction variation. Data from 16 hot-mix asphalt (HMA) paving projects are applied to the ANOVA models. Results of these models then provide insight to contractors where limited quality control testing resources should be expended to minimize process variation and provide an opportunity to make quantitative process improvements.