National Concrete Pavement Technology Center

Project description

State departments of transportation (DOTs), as part of their routine practice, employ quality assurance (QA) procedures based on certifications, inspections, sampling, and testing in their acceptance process for highway pavement construction. The QA requirements are generally in accordance with the federal regulations for construction QA procedures (23 CFR, Part 637B) as well as the recommendations of the Federal Highway Administration (FHWA) and the American Association of State Highway and Transportation Officials (AASHTO) for QA programs. However, one thing generally absent from these programs or plans is the utilization of nondestructive testing (NDT) methods in the QA process. Several studies in recent years have identified the potential advantages of incorporating NDT methods into the QA process for highway pavement construction. These NDT methods are considered to provide an “added value” in the QA process since they potentially allow for (1) quickly assessing product uniformity in real-time as construction progresses; (2) identifying potential defects during construction to allow for timely corrective actions; (3) more frequent inspecting, testing, and replicating without the damaging effects of coring and other destructive testing; and (4) minimizing testing and inspection costs, while improving construction quality. For example, for concrete, the NDT methods can evaluate concrete properties, uniformity, honeycombing, segregation, and cover depth as well as detect reinforcement and dowel bar location and characteristics. Similarly, for asphalt mixtures, the NDT methods can assess properties and conditions such as density, stiffness, thickness, and thermal uniformity. However, despite their high potential and usefulness, the transition of NDT methods from research and forensic investigation to DOTs’ QA process has been rather limited. This is because of the relative complexity of some NDT technologies, inadequate training of QA technicians and inspectors in their use, reluctance to adopt a new technology, and a lack of guidance on how to incorporate the NDT technologies into the overall QA program. The objective of this research is to develop a guidance manual to assist state DOTs in selecting and incorporating NDT methods into their QA programs for highway pavement construction.