Hot in Place Recycling
FHWA-Approved Pavement
Preservation Technique


Q. Why is a surface course or surface treatment required AFTER HIR?
A. HIR effectively re-mediates the existing 1.5" of pavement by re-establishing its “ride-ability” and softening the properties of the oxidized road with the rejuvenating agent. The process itself will retard reflective cracks and essentially turn that existing wearing course into a new leveling course. And much like a leveling binder, it too needs to be sealed/capped with a surface treatment, chip seal or hotmix overlay.
Q. What is the most recommended surface course?
A. Your budget, service life expectation and traffic load will dictate what surface treatment or overlay is most appropriate. However, a chip seal with a fog seal or 1-2" of hotmix asphalt is most typical.
Q. What is the recommended thickness of the final wearing course to be applied after HIR?
A. Most agencies opt for 1-2" of hotmix when a structural increase is desired. For projects that do not require additional structure, most agencies choose a chip seal with a fog seal or 1" of hotmix. Micro-surfacing or slurry seal are popular options in some parts of the country as well.
Q. What is the typical service life of an HIR pavement?
A. That depends on a couple of factors: the final surface treatment or overlay; the traffic loads; the climate; how much overall structure exists on the pavement after treatment and overlay. However, when compared to a standard 2" mill & hotmix overlay, HIR with a 1" hotmix overlay typically delivers the very same life expectancy. HIR with a chip-seal typically lasts 8-10 years.
Q. Is there a project minimum quantity desired?
A. Ideally HIR projects will have a minimum of 75,000 square yards encompassed in 1-3 locations.
Q. can chip sealed pavements benefit from the HIR process?
A. Yes, sometimes. The oil content of the road should be tested to determine whether or not it is a suitable candidate. Too much oil can produce excessive smoke.
Q. How soon does it need to be capped/overlaid afterwards?
A. A pavement that has received HIR should be surface treated, chip sealed or hotmix overlaid within 10 working days.
Q. Can rubberized hotmix asphalt pavements benefit from the HIR process?
A. Yes, there are no issues with using the HIR process on rubberized hotmix pavements.
Q. Is there a minimum pavement thickness required to make it an eligible candidate?
A. Yes, a minimum of 3" of hotmix and/or chip seal is required.
Q. Where does the HIR process typically fit?
A. HIR is used by public works departments in urban and suburban/residential settings just as much as it is used by counties in rural areas.
Q. What is needed to determine whether or not a pavement is a good candidate for HIR?
A. On a structurally-sound pavement, pre-bid pulling of cores (seven 6" cores per unique pave) is required so a materials testing lab can benchmark various key properties of the existing pavement (e.g., penetration value/softness, AC content %, Dust to AC %) before and after adding rejuvenating agent.
Q. Is providing cores necessary if I know the thickness and contents of the pavement?
A. Yes, visual observation of the pulled cores allows the lab to verify pavement thickness and absence of road fabric (Petromat). More importantly, the results of the lab testing allow the lab to confirm to the agency whether or not the pavement is a good candidate for the HIR process.
Q. Who does the recommended testing of the cores?
A. The HIR contractor does NOT do the testing. It is highly recommended the agency hire an AMRL-certified materials testing laboratory that can perform the specific tests. Chicago Testing Laboratory, Inc. specializes in doing the exact tests needed (e.g., AASHTO R59, T30, T49,T164, T166, T209, T269, ASTM D5).
Q. What kind of rejuvenating agent is used?
A. Typically it is simply specified as a non-proprietary rejuvenating agent (ideally an oil, as opposed to an emulsion) capable of effectively softening the existing asphalt pavement.
Q. What is the standard way for putting this out for bid?
A. Most agencies either put it out as a “stand-alone” contract to bid on, or as part of a larger scope of work that includes the hotmix overlay. When put out as a stand-alone contract, the HIR contractor would bid it directly to the agency. When put out as part of a larger contract, the HIR contractor would typically bid as a subcontractor to the various prime contractors bidding the project.
Q. Can I put it out for bid as an Alternate?
A. Yes, however there is a high likelihood the HIR contractor may not bid it since the prime contractor now has the ability to inflate the quoted price—making it “cost prohibitive” to the agency.
Q. Can I be sure more than one HIR contractor will bid my project?
A. Simply put, there is no guarantee more than one contractor will bid your project, as is the case with any project. However, this does NOT mean it is a “sole source method or proprietary.” If we bid your project, it will be bid competitively.