Skip to contentUnited States Department of Transportation - Federal Highway AdministrationSearch FHWAFeedback

Pavements

<< PreviousContentsNext >>

Pavement Recycling Guidelines for State and Local Governments
Participant's Reference Book

PDF Version (72 kb)

Appendix B: New Mexico State Highway And Transportation Department
Special Provisions For In-Situ Cold Recycling With Hot Hydrated Lime Slurry
Section 305-A

NH-285-2 (17) 78
May 6, 1996

All provisions of the New Mexico State Highway and Transportation Department's Standard Specifications for Highway and Bridge Construction shall apply in addition to the following:

305.1. Description

305.11. This work shall consist of pulverizing the existing surfacing to the specified width and depth, mixing an emulsified binder agent, hot hydrated lime slurry, and water if required, with the pulverized surfacing, spreading and compacting said mixture to the specified width and thickness, and sealing of the compacted surface if required. All work shall be as shown on the plans and as provided herein unless otherwise directed by the Project Manager.

305.2. Materials

305.21. The emulsified binder agent shall be Polymerized High Float Emulsion of the type shown on the plans with the option to change one grade up or down at a change in unit price based on a difference in invoice prices for the different grades of emulsion. Changes in grade of binder agent shall be made only with the concurrence of the Project Manager. The Polymerized High Float Emulsion shall meet the requirements of Section 402 - Bituminous Materials, Hydrated Lime, & Liquid Anti-Stripping Agents.

305.22. The cold recycled material shall meet the following gradation requirements:

Table 1. Cold recycled pavement gradation requirements.
Sieve SizePercent Passing
1¼"100
1"90-100

305.23. The sealing emulsion shall be diluted with High Float Emulsion, CSS-1h or other approved equal.

305.24. The lime used for the production of the hot hydrated lime slurry shall be a high calcium pebble quicklime meeting the requirements of ASTM C 977.

305.25. The water used for the production of hot hydrated lime slurry shall be clear and free of deleterious amounts of acid, oil, alkali, organic matter, salt, sugar, or other detrimental material. Water meeting the requirements of Subsection 510.25 Water, is acceptable.

305.26. The hot hydrated lime slurry shall have a minimum dry solids content of 35 percent by weight and shall consist of a uniform, pumpable suspension of solids in water.

305.3. Construction Requirements

305.31. General. The existing surfacing shall be cold recycled in a manner that does not disturb the underlying material in the existing roadway.

Prior to initiating recycling operations or other inherent work, the Contractor shall clear, grub, and remove all vegetation and debris within the width of pavement to be recycled. Disposal of said vegetation and debris shall be as directed by the Project Manager.

The Contractor may add water to the pulverized material for the purpose of cooling the cutting teeth on the mill or pulverizing equipment or to facilitate uniform mixing with the emulsified binder agent. Water may be added prior to or concurrently with the emulsified binder agent. A means shall be provided for accurately metering and registering the rate of flow of water into the pulverized material.

When the typical section that is to be recycled is situated on a super elevated or sloped section, the initial pass of the milling equipment shall begin at the lowest portion of the section and proceed in succession towards the higher end of the slope.

Fillets of fine, pulverized material which form adjacent to a vertical face shall be removed prior to spreading the recycled mix, except that such fillets adjacent to existing pavement which will be removed by overlapping during a subsequent milling operation need not be removed.

If segregation occurs either in the windrow or behind the paver, the Project Manager may require the Contractor to make changes in the equipment or operations. These changes may include, but shall not be limited to, the following:

  1. Reducing the forward speed of the milling operation.
  2. Increasing the amount of material going through the crusher.
  3. Adjusting the crusher to produce more fines.
  4. Adjusting the height of free fall of material from the mixing unit.
  5. Adjusting the amount of water in the mixture.

The Contractor may be required to make other changes in his equipment or operations, as necessary to obtain a satisfactory end-product.

When a paving fabric is encountered during the cold recycled in-situ operation, the Contractor shall make the necessary adjustments in the equipment or operations so that at least 90 percent of the shredded fabric in the recycled is five square inches or less in size. Additionally, no fabric piece shall have any dimension exceeding a length of four inches. These changes may include but not be limited to adjusting the milling rate, adding or removing screens, etc, in order to obtain a specification end product. The Contractor shall be required to waste material containing oversized pieces of paving fabric as directed by the Project Manager. These changes will be made at not additional cost to the Department.

The recycled bituminous base shall be spread in one continuous pass, without segregation, to the typical section shown on the plans.

305.311. Surface Tolerance. The final surface of recycled bituminous base shall not deviate in excess of ½ inch from the testing edge with a 10-foot straightedge resting on any two points. all deviations from this tolerance shall be corrected at no additional cost to the Department.

305.32. Temperature & Weather Limitations. Recycling operations shall not be performed when the atmospheric temperature is below 60°F or when the chill factor is below 35°F or when the weather is foggy or rainy or when weather conditions are such that in the judgement of the Project Manager, proper mixing, spreading and compacting of the recycled material cannot be accomplished. The chill factor shall be as defined in Subsection 401.341 Temperature & Weather Limitations.

305.33. Binder Application. When commencing recycling operations, the emulsified binder agent shall be applied to the pulverized material at the rate determined by the Department based on samples obtained by the Contractor for the mix design. The exact application rate of the emulsified binder agent will be determined and varied by the Project Manager as required by existing pavement conditions. An allowable tolerance of plus or minus 0.2 percent of the initial design rate or of the rate determined by the Project Manager of application shall be maintained at all times.

305.34. Lime Slurry Addition. The quicklime shall be slaked with the required amount of water and uniformly incorporated into the pulverized surfacing at a rate that will result in 1.5% hydrated lime by dry weight of pulverized surfacing. The amount of lime slurry being added shall be controlled by the continuous weighing of the pulverized surfacing.

305.35. Density & Rolling Requirements. The Contractor shall establish a rolling pattern such that a minimum density of 96 percent of a laboratory briquette, prepared in accordance with Department molding and testing procedures, is obtained. The Project Manager may require a re-demonstration of rolling capabilities when a change in the recycled materials is observed, whenever a change in rolling equipment is made, or if densities are not being obtained with the rolling pattern being used.

Initial rolling shall normally be performed with a 30 ton pneumatic roller and continued until no displacement is discerned or until the pneumatic rollers have walked out. If necessary, in order to initially seat the mixture, one or two passes with a small pneumatic roller may be made prior to application of the 30 ton roller. Final rolling to eliminate pneumatic tire marks and achieve density shall be done by steel wheel roller(s), either in static or vibratory mode, as required, to achieve required density.

Rolling shall be performed in accordance with Subsection 401.35 Compaction.

Rollers shall not be started or stopped on uncompacted recycled material. Rolling shall be established so that starting and stopping will be on previously compacted recycled material or on existing PMBP.

Rolling which results in cracking, movement, or other types of pavement distress shall be discontinued until such time as the problem can be resolved. Discontinuation and commencement of rolling operations shall be at the sole discretion of the Project Manager.

305.36. Finishing Operations. After the recycled material has been spread and compacted, vehicles, including Contractor's equipment, shall not be permitted on the completed recycled bituminous base for at least two hours. The area may then be opened to all traffic and shall be allowed to cure such that the free moisture in the recycled material is reduced to one percent or less above the natural moisture of the material by total weight of mix, before placing the surfacing.

The surface of the recycled pavement shall be maintained in a condition suitable for the safe accommodation of traffic. All loose aggregate that develops on the surface of the recycled pavement shall be removed by power brooming. After the free moisture content of the recycled material is one percent or less above the natural moisture of the material, the Project Manager may require that the surface be sealed with emulsion at an approximate rate of 0.05 to 0.10 gallon per square yard in order to control surface raveling.

All unacceptable recycled bituminous base shall be repaired by the Contractor, as directed by the Project Manager prior to placing a subsequent surfacing course. Said repair(s) shall be made at no additional cost to the Department.

305.37. Equipment.

305.371. Cold In-Situ Machinery. The Contractor shall furnish a self-propelled machine capable of pulverizing in-situ bituminous materials to the depth shown on the plans in one pass. The machine shall have a minimum rotor cutting width of 12 feet, standard automatic depth controls and shall maintain a constant cutting depth. The machine shall also incorporate screening and crushing capabilities to reduce or remove oversize particles prior to mixing with emulsion. Oversize particles shall be reduced to size by crushing, however, the Contractor may, with concurrence of the Project Manager, waste up to a maximum of two percent oversize material prior to adding emulsion. This waste shall generally be limited to that material which is flattened out rather than broken down by the crusher.

The emulsified agent shall be applied through a mixing machine capable of mixing the pulverized material and the emulsified binder agent to a homogeneous mixture and placing the mixture in a windrow. The method of depositing the mixed material in a windrow shall be such that segregation does not occur.

A positive displacement pump, capable of accurately metering the required quantity of emulsified binder agent, into the pulverized material, shall be used. The pump shall be equipped with a positive interlock system which will permit addition of the emulsified binder agent only when the pulverized material is present in the mixing chamber and will automatically shut off when the material is not in the mixing chamber.

Each mixing machine shall be equipped with a meter capable of registering the rate of flow and total delivery of the emulsified binder agent introduced into the mixture. The meter shall be calibrated by the Contractor, in the presence of the Project Manager, before commencing recycling operations. Subsequent checks or calibrations of the meter shall be as directed by the Project Manager.

305.372. Lime Slurry Equipment. The lime slurry shall be produced at the job site using a batch type process. The equipment shall accurately proportion the quicklime and water; adequately mix the two to obtain proper slaking; and maintain a uniform, homogeneous slurry.

Transports used to convey the slurry to the roadway shall employ sufficient agitation to prevent settlement and maintain a uniform homogeneous mixture.

The lime slurry shall be added to the pulverized surfacing by a spray bar located at the cutting head on the milling machine. A metering device shall be used and it shall accurately measure the amount of slurry delivered to within plus or minus 10 percent by weight.

305.373. Pavers. Placing of the recycled bituminous base course shall be accomplished with a self-propelled bituminous paver meeting the requirement of Subsection 401.323 Pavers, except that heating of the screed will not be permitted. This equipment shall be capable of spreading the recycled bituminous base in one continuous pass, without segregation, to the typical section shown on the plans.

When a pick-up machine is used to feed the windrow into the paver hopper, the pick-up machine shall be capable of picking up the entire windrow down to the underlying materials.

305.374. Rollers. Rollers shall meet the requirements of Subsection 401.324 Compaction Equipment. The number, weight, and type of rollers shall be sufficient to obtain the required compaction while the mixture is in a workable condition except that one pneumatic roller shall be 30 ton minimum weight. All rollers shall be equipped with pads and a water system which prevents sticking of the recycled mixture to the roller wheels.

305.375. Brooms. The Contractor shall have on hand at all times a rotary power broom maintained in good working order and of a design suitable for removing aggregate that becomes dislodged from the surface of the recycled surface.

305.4. Method Of Measurement

305.41. In-situ cold recycling of existing surfacing will be measured by the square yard.

Polymer modified high float emulsion will be measured by the ton.

Sealing emulsion will be measured by the ton. Quicklime will be measured by the ton.

305.5. Basis Of Payment

305.51. In-situ cold recycling of existing surfacing will be paid for at the contract unit price per square yard.

Polymer modified high float emulsion will be paid for at the contract unit price per ton.

Sealing emulsion will be paid for at the contract unit price per ton.

Quicklime will be paid for at the contract unit price per ton. This price will be full compensation for the quicklime, and production of the hot lime slurry including all necessary equipment, labor, and water.

Payment will be made under:

Pay ItemPay Unit
In-Situ Cold Recycling of Existing SurfacingSquare Yard
Polymer Modified High Float Emulsion (Type)Ton
Sealing EmulsionTon
QuicklimeTon
PDF files can be viewed with the Acrobat® Reader®
<< PreviousContentsNext >>
 
Updated: 04/07/2011
 

FHWA
United States Department of Transportation - Federal Highway Administration