11. Quality Assurance

11.2.1 Quality Assurance

The definition of QA has evolved over the years. Earlier definitions described QA primarily as the methods employed by the owner/agency to ensure that they receive a quality product, a definition now closer to the term “acceptance.” Two documents are now referenced for definitions in this area: AASHTO R 10, “Definition of Terms Related to Quality and Statistics as Used in Highway Construction,” and TRB Circular E-C173, “Glossary of Transportation Construction Quality Assurance Terms.” Airfield specifications such as FAA’s P-401 and the DoD UFGS 32 12 15.13 use most of the terms synonymously with the AASHTO and TRB documents, but not always.

AASHTO R 10 defines QA as, “(1) All those planned and systematic actions necessary to provide confidence that a product or facility will perform satisfactorily in service; or (2) making sure the quality of a product is what it should be.” QA addresses the overall process of obtaining the quality of a service, product, or facility in the most efficient, economical, and satisfactory manner possible. QA includes the elements of QC, independent assurance, acceptance, dispute resolution, etc. QA involves continued evaluation of the activities of planning, design, development of plans and specifications, advertising and awarding of contracts, construction and maintenance, and the interactions of these activities.

11.2.2 Quality Control

AASHTO R 10 defines QC as, “The system used by a contractor to monitor, assess, and adjust their production or placement processes to ensure that the final product will meet the specified level of quality. Quality control includes sampling, testing, inspection, and corrective action (where required) to maintain continuous control of a production or placement process.” QC is also known as “process control.”

Public and private airfields often rely on contractor QC as a major part of their QA program, providing few, if any, agency inspectors. This does not mean that inspection is not done, or that quality suffers. Airfield agencies like FAA and DoD generally rely on different mechanisms than DOTs to accomplish the same goal of quality.

Airfield agencies like FAA and DoD generally rely on different mechanisms than DOTs to accomplish the same goal of quality.

11.2.3 Acceptance

AASHTO R 10 defines acceptance as, “The process whereby all factors used by the agency (i.e., sampling, testing, and inspection) are evaluated to determine the degree of compliance with contract requirements and to determine the corresponding value for a given product.”

QC measurements (sampling, testing, and inspection) may or may not be used in the acceptance decision process. When contractor test results are used in the agency’s acceptance decision, the process often includes agency verification and/or dispute resolution mechanisms.

11.2.4 Dispute Resolution

Agency and contractor labs sometimes generate conflicting test results. It is important for specifying agencies to outline a process to resolve conflicts that may occur. AASHTO R 10 defines dispute resolution as, “The procedure used to resolve conflicts resulting from discrepancies between the agency’s and contractor’s results of sufficient magnitude to impact payment.”

As an initial step, agencies may simply review multi-laboratory precision statements in AASHTO and/or ASTM to see if test results are within the acceptable range of two test results. A dispute resolution procedure may also include the testing and comparison of independent samples. Agencies may apply some type of statistical test (t-test) to determine for a group of test results how far apart is too far apart. The independent t-test is used to compare the means of two independently obtained sets of data. The paired t-test compares test results of split samples. If disputes cannot be resolved between the agency and contractor, third-party arbitration may be the final step.