Heating, recycling, and laydown. The HIR process includes heating (generally using either radiant or infrared heating to minimize emissions and damage to the asphalt binder) and scarifying the existing pavement surface (typically maximum depth of 2 in.). The scarified material is typically remixed with additional aggregate, binder, and recycling agent (as necessary) and placed back on the roadway in a single pass. Examples of the HIR process are shown in Figure 10-20 through Figure 10-22. Compaction. Typical asphalt compaction equipment and processes are used. Wearing surface application. The HIR surface may be left as the final wearing surface, overlaid with asphalt if increased structural capacity is needed, or chip sealed. Table 10-10. Key characteristics of hot in-place recycling. Pavement Performance Conditions Addressed Contraindications Indicators Affected Functional/Other Structural failure (i.e., + Non-load-related transverse Thermal and surface extensive fatigue cracking cracking. cracking. and/or structural rutting). + Load-related alligator Raveling/weathering. Distresses deeper than range cracking. Friction loss. of treatment effectiveness. + Load-related, surface Bleeding. Urban road sections. initiated cracking. Roughness. + Asphalt rutting. Corrugation. + Smoothness. Rutting. + Friction. Structural Low severity top-down cracking. Adds some structural benefit. Expected Life 5 to 15 years. sealant should be removed prior to placement to reduce risk of flash fires or excessive blue smoke. Recommended to repair localized structural problems prior to placement. Presence of rubber in the surface lift (rubberized seals, some crack fillers, and similar sources) requires special attention during the mix design process. Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. Remarks Although treatment can perform well in all climatic conditions, placement should not occur when temperature is below 50 °F, or when it is raining. Appropriate for all traffic volumes; however, the heat scarification process should be used for only low-volume roads. Due to the length of the recycling equipment train, short road Additional sections, particularly in urban settings, are not suitable. Require mix design to determine quantities of new materials, additives. Characterization of in place materials should consider material variability and adequacy of lift thicknesses.
Heating, recycling, and laydown. The HIR process includes heating (generally using either radiant or infrared heating to minimize emissions and damage to the asphalt binder) and scarifying the existing pavement surface (typically maximum depth of 2 in.). The scarified material is typically remixed with additional aggregate, binder, and recycling agent (as necessary) and placed back on the roadway in a single pass. Examples of the HIR process are shown in Figure 10-20 through Figure 10-22. Compaction. Typical asphalt compaction equipment and processes are used. Wearing surface application. The HIR surface may be left as the final wearing surface, overlaid with asphalt if increased structural capacity is needed, or chip sealed. Table 10-10. Key characteristics of hot in-place recycling. Conditions Addressed Contraindications Pavement Performance Indicators Affected Functional/Other Thermal and surface cracking. Raveling/weathering. Friction loss. Bleeding. Roughness. Corrugation. Rutting. Structural Low severity top-down cracking. Adds some structural benefit. Structural failure (i.e., extensive fatigue cracking and/or structural rutting). Distresses deeper than range of treatment effectiveness. Urban road sections. + Non-load-related transverse cracking. + Load-related alligator cracking. + Load-related, surface initiated cracking. + Asphalt rutting. + Smoothness. + Friction. Expected Life 5 to 15 years. Additional Remarks sealant should be removed prior to placement to reduce risk of flash fires or excessive blue smoke. Recommended to repair localized structural problems prior to placement. Presence of rubber in the surface lift (rubberized seals, some crack fillers, and similar sources) requires special attention during the mix design process. Pavement surface must be dry and swept clean of dirt, sand, gravel, and other surface contaminants. Although treatment can perform well in all climatic conditions, placement should not occur when temperature is below 50 °F, or when it is raining. Appropriate for all traffic volumes; however, the heat scarification process should be used for only low-volume roads. Due to the length of the recycling equipment train, short road sections, particularly in urban settings, are not suitable. Require mix design to determine quantities of new materials, additives. Characterization of in place materials should consider material variability and adequacy of lift thicknesses.