music ♫ When it comes to meeting quality goals on construction projects, we’ve been down this road before! How do we create specifications that meet our needs for quality and performance in the future? Quality Assurance Specifications are specifications
that require contractor quality control and agency acceptance activities throughout production
and placement of a product. They offer a balance between materials and
methods specifications and warranty specifications. A well-written Quality Assurance Specification
can provide owner agencies a higher level of confidence that the quality requirements for
the final product are being met. They clearly delineate contractor and agency responsibilities, separate quality control and acceptance functions, and base payment on the measured construction quality level. How do Quality Assurance Specifications work? Quality assurance specifications typically
call for one or more attributes or “Quality Characteristics” to be checked during production or placement. The allowable limits for these quality characteristics are statistically-based and use methods such as random sampling and lot-by-lot testing. This proactive quality evaluation during construction, lets the contractor know if the operations
are producing an acceptable product, and lets the agency make acceptance decisions. The Quality Assurance Specification should include the right quality characteristics,
whose metrics contribute to either meeting intended engineer properties and/or the long-term
performance of a given material. They consider the targets and limits within
which the material or work can be produced to ensure good performance over the design
life of the product. For concrete pavements, examples of typical quality characteristics are entrained air content thickness, and smoothness. For asphalt pavements, typical quality characteristics are the density of the compacted pavement or air voids, binder content, voids in mineral aggregate also known as VMA, and pavement smoothness. Quality Assurance Specifications acknowledge that the contractor directly controls quality of the final product through material selection, mix design, production control, and final placement. Quality Assurance Specifications will commonly require quality control activities to be performed by the contractor. Contractor activities include developing a quality control plan, monitoring and assessing production or placement processes through inspection, sampling, and testing. This information is used to perform adjustments and corrective actions in real time in accordance with the approved quality control plan to control the level of quality of the product. The agency is responsible for verification testing and acceptance of the product based on established targets and limits. The agency does not control the quality of the product. They simply influence the quality of the product by specifying the payment for the quality received. Agency technicians and inspectors should monitor the contractor’s quality control activities but still have the essential responsibility for acceptance. Inspection, sampling, and testing are all
used by an agency to determine the degree of compliance with approved quality control plans and contract requirements. For each quality characteristic,
Quality Assurance Specifications specify the pay and acceptance limits, along with the percentage of material that must be within specified limits for material to be considered acceptable. During construction, samples within a lot are tested, and statistical analysis performed to determine percent within the limits for that lot. For example, when using the percent within limits quality measure. Quality Assurance Specifications must also include independent agency verification testing and processes with appropriate statistics-based comparisons when contractor test results are used by the agency for acceptance purposes. If the contractor meets or exceeds established targets the specifications should provide increased payment,
or incentive bonus, typically up to 105 percent for superior quality work. If the contractor misses the mark, the specifications include consequences through pay adjustment disincentives, corrective actions, or remove and replace. In extreme cases, reduced payment can be as low as 50 percent. Unacceptable results from a series of consecutive tests, could also result in a change in frequency of sampling and testing to address product quality trends. Quality Assurance Specifications: Recognize the inherent variability of materials, processes, sampling, and testing. Identify the specific quality characteristics to be measured for acceptance. Assign quality control sampling, testing, and inspection to the contractor. Include acceptance sampling, testing, and inspection by the agency. Provide price adjustments related to quality level of the product. While the goal of Quality Assurance Specifications is to improve construction quality by establishing targets and performing testing and statistical analysis, the targets and price adjustments
are not necessarily established based on performance predictions. “Improved” Quality Assurance Specifications, wherein the quality characteristics are related
to the likely performance of the in-place product through mathematical modeling, which
is then used as a rational basis for establishing targets and price adjustments, are known as
Performance Related Specifications. To learn more about Quality Assurance Specifications,
visit our website at www.fhwa.dot.gov/research Help with writing and implementing specifications
and with construction quality assurance are available through the FHWA resource center
and through NHI Courses 134001, Principles and Applications of Highway Construction Specifications and 131141, Quality Assurance for Highway Construction Projects. ♫ music ♫