There are several different types of specifications for concrete pavement contracts. The most common remains the method and material specification (also called method specification, or recipe specification). This type of specification directs the contractor to use specified materials in definite proportions and specific types of equipment and methods to place the pavement. (Each step is directed by an inspector or engineer from the agency.)
End Result Specifications
End result specifications require the contractor to take the entire responsibility for supplying the pavement. The agency’s responsibility is to accept or reject the pavement or apply a price adjustment based on how the pavement measures against acceptability criteria. End result specifications afford the most flexibility to the contractor for innovation. There are very few agencies using this specification in its pure form.
Quality Assurance/Control Specifications
Presently, many highway and airport agencies are starting to use or develop specifications encompassing quality assurance and quality control measures. Quality assurance/quality control (QA/QC) specifications are a combination of end-result specifications and method and materials specifications. The contractor is responsible for quality control (process control), and the owner/engineer is responsible for acceptance of the product. Quality assurance specifications typically are statistically based specifications that use methods such as random sampling and lot-by-lot testing, which let the contractor know if his operations are producing an acceptable product.
While it is not clear whether QA/QC or performance-related concepts are necessary and cost-effective for smaller projects, in time it is likely they will become the standard for larger projects.
The fourth type of specification, performance-related, describes how the pavement should perform over time. This requires sound information on what defects or quality factors exist in the as-constructed pavement that will accurately predict its performance. This specification concept is relatively new to the construction of pavements and has not been implemented by any state transportation departments to date.