<p><p><h2>Summary of Example Specifications</h2><strong>Hot In-Place Recycling (HIR) Guidelines and Specifications Example</strong></p><p>The necessary steps required for ensuring satisfactory construction of a hot in-place recycling (HIR) project are the development of an adequate specification, and ensuring that the specification requirements are met during mix design and construction. Also, a set of guidelines or specifications is required in hot in-place recycling to describe the materials, workmanship, and other general requirements for the project. Where appropriate, agencies should consider the hot in-place recycling process along with other alternatives. This process can help the user agency to evaluate two or more methods and determine the most cost effective approach.</p><p>A set of general specification guidelines for effective completion of hot in-place recycling process is presented in the table below. The major steps involved are preliminary pavement evaluation to determine structural adequacy, determination of applicability of hot in-place recycling, a detailed pavement evaluation, and selection of the particular hot in-place recycling technique.</p><p>Before any rehabilitation process is specified, the most suitable rehabilitation process should be determined on the basis of the source and cause of any surface defects such as rutting, cracking and/or deficient surface frictional resistance. If the cause of the defect remains unknown, then the proper rehabilitation technique cannot be applied, and the defect would most likely reappear in future.</p><p>General steps for a HIR project (FHWA-SA-98-042 Report)<br><img class="wp-image-2475 size-full alignnone" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="A table showing the general steps for a HIR project (FHWA-SA-98-042 Report)." width="592" height="355" /></p><p>Table below presents the information required for evaluation of the existing pavement so that a proper recycling process can be specified. The information required include an inventory information, details about the pavement structure, knowledge of the prior treatments, geometry and profile of the pavement, and the presence of miscellaneous structures such as manholes or utility covers on the pavement. These information help the user agency to evaluate the applicability of the hot in-place recycling process, determine the need for any prior treatment (such as cold milling), and specify the particular hot in-place recycling technique applicable (such as remixing or repaving).</p><p>The information from detailed evaluation of existing pavement surface is also important. The most important surface features which must be evaluated, include cracks, wear, and rutting while important existing HMA features include thickness, binder content, grading, density, and penetration and viscosity of the binder. Surface recycling is employed to improve the profile of a surface course deformed by rutting or wearing, but in comparatively unaged condition with minor cracking.</p><p>Repaving is used to improve the profile of a surface course severely deformed by rutting or wearing, with new hot-mix overlay placed in one pass. This method improves frictional characteristics, and provides some pavement strengthening. Remixing can be used to improve the quality of old, cracked, aged surface course by the addition of recycling agent and/or new hot mix asphalt. The existing HMA mixture should be evaluated to help specify the particular hot in-place recycling technique required and to determine the type and amount of any recycling agent required. The process basically consists of extraction and recovery of the asphalt binder from the mix, up to the scarification depth. The type and amount of recycling agent chosen should be such as to restore the binder to the as-placed rheological condition. Adjustments of amount of recycling agent may be required in the field, since laboratory evaluations often indicate more recycling agent than is actually needed.</p><p>Preliminary pavement structure evaluation information (FHWA-SA-98-042 Report)</p><p><img class="alignnone wp-image-2476 size-full" src="https://www.geoinstitute.org/sites/default/files/geotech-tools-uploads/…; alt="A table showing the preliminary pavement structure evaluation information (FHWA-SA-98-042 Report)." width="564" height="642" /></p><p>For construction guidelines in specifications for recycling, the average recycled mixture temperature required for satisfactory compaction is in the 105° C to 115° C (221° F to 239° F) range at the breakdown rolling, depending on specific site and ambient condition, and for scarification of the existing old HMA to be effective and efficient, the minimum temperature at the depth of the scarification should be the softening point for the project’s recovered asphalt cement before rejuvenation.</p><p>&nbsp;</p></p>

<div class="sub-block" id="rubblization-specifications-example"><h2><span style="font-size: 12pt;">Rubblization Specifications Example</span></h2>
<p><strong>&nbsp;</strong>Most specifications require the excavation of a 1.2 by 1.2 m (4 by 4 ft) test pit to ensure that the PCC has been fractured throughout its entire thickness and that the bond between any distributed steel and concrete has been broken. Most highway specifications have particle size requirements for broken PCC at the surface and through the depth of the slab, The range for typical maximum particle size at the surface for the vast majority of specifications is from 50 to 150 mm (2 to 6 inches). The range for typical maximum particle size through the depth of the slab for the vast majority of specifications is from 150 to 450 mm (6 to 18 inches). The test pit is usually excavated using a backhoe or similar equipment and patched using crushed stone or HMA as for repairing soft spots. Surface rolling is performed to prepare the surface for placing the overlay. Proof rolling with a heavy pneumatic-tired roller or loaded dump truck is performed when there are concerns regarding unstable subgrade, voids under the concrete or severely deteriorated joints. Excessively yielding areas are marked and repaired prior to placing the asphalt overlay. Vibratory smooth drum rollers (min. 9000 kg, 10 tons) operating at the highest frequency setting available are required by specification, as are pneumatic-tired rollers in some states. Two to four passes of the vibratory roller, depending on how the material responds to rolling, are normally applied, with the roller operating at a forward speed that results in at least 33 impacts/meter (10 impacts/ft). &nbsp;A few specifications state that water may be used in compaction but this is not standard practice in most states. Some early rubblizing specifications required the use of a heavily ballasted (31,750 to 45,350 kg, 35 to 50 ton) pneumatic-tired roller, similar to what has been used when cracking and seating or breaking and seating PCC pavements. This is not recommended for rubblized PCC, particularly on sites with questionable foundation conditions. As with vibratory rollers, the same pneumatic rollers used for rolling HMA are suggested for rolling rubblized PCC. After any soft areas have been patched and rolling is complete, the surface is ready for HMA paving operations. There is disagreement on the necessity of applying a tack or prime coat to the surface of the rubblized PCC. On one project where a diluted, slow-setting asphalt emulsion was applied, there were places where construction traffic marred the surface by picking up conglomerations of fine particles and asphalt. While this did not appear to cause major problems with the HMA paving operation, it was inconvenient and some areas had to be filled and tamped with aggregate materials or HMA ahead of the paving machine.</p>
<p>Once the PCC pavement has been rubblized and rolled, construction proceeds in the same manner as for a new or reconstructed thick asphalt pavement structure. Placement of the HMA overlay is usually performed in two or three lifts, depending on the overlay thickness and traffic control requirements. The most notable difference is in the placement of the HMA base course directly over the rubblized PCC, since there is more variance in the profile of rubblized PCC than there usually is for a finished aggregate base course. As the finished grade of the prepared rubblized PCC may be slightly higher than the original profile this should be taken into account when developing profile elevations of the finished surface and plan quantities for the HMA overlay.</p>
<p>Traffic is not routed over the rubblized surface until it is covered with an adequate thickness of HMA. This is for safety and to avoid loosening of surface particles. Where rubblization has been performed on relatively thin PCC pavements or soft supporting conditions, allowing traffic onto the rubblized pavement should be avoided until there is sufficient overlay thickness to avoid subgrade deformation under traffic. For Interstate highways, it is most common to place at least 150 mm (6 in.) of HMA before moving traffic onto the rubblized pavement. The total overlay thickness required depends on the subgrade support, thickness of the rubblized concrete, and projected traffic. Total HMA thickness for Interstate highway projects typically ranges from about 200 mm to 350 mm (8 to 14 in.).</p>
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