Variability in Pavement Materials and Construction

Variability is inherent in all pavement materials and construction processes. Understanding the magnitude of variability is important to pavement construction industry stakeholders. State departments of transportation (DOTs) need to quantify the typical variability of pavement materials and construction processes to establish rational specification limits. Material producers and contractors need to identify and measure sources of variability to manage quality. While quality has traditionally been defined as “fitness for use” or “degree of excellence,” a modern definition of quality states, “quality is inversely proportional to variability.” Relating pavement material properties to variability has traditionally relied on quality characteristics such as binder content, aggregate gradation, mix volumetrics, in-place density and smoothness for asphalt pavement, and compressive strength, air content, thickness, permeability, and smoothness for concrete pavement. NCHRP Synthesis of Highway Practice 232: Variability in Highway Pavement Construction (1996) published typical variabilities for many of these quality characteristics. However, in the past 25 years, improvements in mix design practices, test equipment and methods, material processing and construction practices, increased use of recycled materials, and changes in state DOTs’ specifications (including improved quality measures such as percent-within-limits and alternative project delivery methods (which typically include advanced quality management program components)) are likely to have impacted variability. In addition, new performance tests such as performance-graded binder tests, asphalt mixture cracking and rutting tests, concrete tests such as the Super Air Meter, and surface resistivity are being introduced, most of which have not been evaluated for typical variability values. As state DOTs move from pavement acceptance based on traditional quality characteristics to performance tests (some of which rely on test methods that cannot be performed as frequently as traditional tests due to testing complexity), it is critical that the variability of pavement materials and construction processes be better understood so that pavements consistently meet the long-term expectations of state DOTs. Also, introduction of nondestructive test methods and technologies, with greater coverage than traditional methods, have the potential to provide a great deal of useful data regarding pavement construction that can be leveraged to improve quality, if their variability is documented. It is also important to know if quality assurance (QA) specifications instituted by many state DOTs since 1996 have resulted in decreased variability, and therefore have resulted in improved pavement quality. The objective of this research is to prepare a report quantifying the typical variability of pavement construction materials and processes and provide guidance for state DOTs to evaluate the variability of newly implemented performance tests.


  • English


  • Status: Proposed
  • Funding: $500000
  • Contract Numbers:

    Project 10-116

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Hanna, Amir

  • Start Date: 20220607
  • Expected Completion Date: 0
  • Actual Completion Date: 0

Subject/Index Terms

Filing Info

  • Accession Number: 01846780
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 10-116
  • Files: TRB, RIP
  • Created Date: May 24 2022 7:34PM