<p><p><h2>QC/QA Guidelines</h2>Quality control (QC) for Hot In-place Recycling (HIR) includes those activities undertaken by the contractor to monitor production and placement of the recycled mix and is intended to eliminate sub-standard materials or poor workmanship to ensure compliance with the specifications. Compliance with the specifications, in turn, ensures the long-term performance of the finished product. Quality Assurance (QA) includes those activities performed by the purchaser, owner, or their agent to ensure that the contractor has met the requirements of the specifications and that the risk of acceptance of the final product will be within acceptable limits. Typically, the inspection and QC/QA plan for a HIR Surface Recycling project will have only one component while a HIR Remix or a Repave project QC/QA plan will have two components: one for the HIR portion of the work and one for the admix or HMA used in the integral overlay portion of the work.</p><p>A recent trend has been towards using QC test results in place of some or all of the QA tests. The rationale for this is to reduce duplication of efforts and costs. However, care must be taken since the QC plan’s objective is to control the quality of the product being produced, at specific control points, on an ongoing basis and not evaluate the acceptability of the finished project.</p><p>A good QC/QA plan is essential to obtaining a satisfactory Cold Recycling (CR) pavement, regardless of the type of specification used. As with any in-place construction, CR can involve the recycling of pavement sections with variability in gradation and asphalt content, due to areas of major maintenance such as patching and chip sealing. A good QC/QA plan must not be so complex as to prohibit changes due to this inherent variability, yet be sophisticated enough to determine the acceptability of the CR process and identify areas of non-uniformity where changes in the process are necessary. The required material sampling and testing should be appropriate for the construction methods and should be related to process control and/or final product performance. CR is a variable process and changes in rolling patterns, moisture content, and recycling additive content will be necessary to obtain optimum performance. The testing and acceptance plan needs to be formulated to identify the need for slight changes in the above procedures and flexible enough to allow for changes without redesign of the mixture.</p><p>For the Full Depth Reclamation (FDR), the inspection and QC/QA plan needs to be developed based on the FDR application, and then amended for the specific type of equipment and stabilizing agent(s) being used on the particular project. During the FDR process, the owner agency/contractor QC/QA plan needs to address specific areas of concern:<br><ul> <li>Treatment depth</li> <li>Gradation</li> <li>Stabilizing agent application rate</li> <li>Moisture content</li> <li>Uniformity</li> <li>Compaction</li> <li>Smoothness</li></ul>To ensure that the automatic treatment depth controls are working correctly on the reclaimer, the treatment depth needs to be physically measured. Depth measurements should be performed on a regular basis by removing the reclaimed material on each side of the reclaimer. Pulverizing the pavement structure fluffs up the material and this needs to be accounted for when determining the treatment depths of subsequent mixing passes. Controlling treatment depth is also important, particularly if the thickness of the existing pavement structure is variable. The gradation of the reclaimed material should be checked periodically. This is to verify the gradation assumptions used in the mix design process and to ensure that the existing asphalt layers are being pulverized to the required maximum particle size. Maximum particle size checks are usually made more often than determination of the overall gradation of the reclaimed material.</p><p>Sampling of the reclaimed material needs to be undertaken with special care to ensure that only the pulverized/mixed materials are sampled. The sample must also be taken from the full treatment depth since a reclaimer operating with the cutting drum in a down cutting mode will bring more of the large sized particles to the surface. If the full treatment depth is not completely sampled, the gradation results will not be representative.</p><p>The water used in the FDR process needs to be clean and free of detrimental concentrations of acids, alkalis, salts, sugars, and other chemical and organic compounds. If the water is not from a potable supply, it will need to be tested to ensure it is suitable, particularly when stabilizing agents are being used. Uniformity of the reclaimed mix is initially checked visually for any segregated areas. Segregated areas can be remixed with the reclaimer or motor grader on an as-required basis. The reclaimed material should be checked for uniformity by ensuring that a sufficient overlap between adjacent passes, both longitudinally and transversely, is being used. Uniformity can also be checked by a comparison of the reclaimed mix gradation in a suspected segregated area with the gradation in a typical area.</p><p>Compaction is one of the critical variables influencing the long-term performance of the reclaimed mix and, therefore, must be continually checked. It is important to confirm the average degree of compaction for the total treatment thickness but also for individual layers. The importance of determining the variation in compaction between the upper and lower layers of the treated thickness increases with increasing layer depths.</p><p>Inspections, construction observations, daily logs, and record keeping are essential QC/QA activities for all technologies. These activities help to ensure and/or verify that<br><ul> <li>Good construction practices and the project specifications are followed</li> <li>Problems can be anticipated before they occur, in some cases</li> <li>Problems that do arise are caught early, and their cause can oftentimes be identified</li> <li>All parties are in good communication</li> <li>The project stays on schedule</li></ul></p></p>