406.01 406-1 SECTION 406 COLD ASPHALT PAVEMENT (RECYCLE) DESCRIPTION
406.01 This work consists of pulverizing the existing asphalt surfacing to the depth shown on
the plans, mixing a recycling agent and water, if required, with the pulverized material, then spreading and compacting the mixed material. MATERIALS
406.02 The recycling agent shall be either a high float emulsified asphalt (polymerized) or
emulsified recycling agent meeting the requirements of subsection 702.02(e). The pulverized material shall meet the following gradation requirements: Table 406 -1 COLD ASPHALT PAVEMENT (RECYCLE) PULVERIZED MATERIAL GRADATION REQUIREMENTS Sieve Size Percent Passing 31.5 mm (1 1/4 inch) 100 25.0 mm (1 inch) 90-100 The sealing emulsion shall be high float emulsion (diluted), emulsified asphalt (SS), or approved equal. CONSTRUCTION REQUIREMENTS
406.03 Weather Limitations . Daily recycling operations shall not begin until the atmospheric
temperature is 55 ºF and rising. Recycling operations shall be discontinued when the temperature is 60 ºF and falling. Recycling operations shall not be performed when the weather is foggy or rainy, or when weather conditions are such that the proper mixing, spreading, compacting, and curing of the recycled material cannot be accomplished. Cold recycled pavement damaged by precipitation shall be reprocessed or repaired by methods approved by the Engineer, at the Contractor’s expense. The construction of cold recycled pavement will not be allowed from September 16 through May 14 unless otherwise approved. The Contractor’s Progress Schedule shall show the methods to be used to comply with this requirement.
406.04 Milling . The existing asphalt surfacing shall be cold recycled in a manner that does not
disturb the underlying material in the existing roadway. Adjacent recycling passes shall overlap at the longitudinal joint a minimum of 4 inches. The beginning of each day’s recycling operation shall overlap the end of the preceding recycling operation a minimum of 100 feet unless otherwise directed. 406.05 406-2 Any fillet of fine, pulverized material that forms adjacent to a vertical face shall be removed before spreading the mixed material, except that such fillet adjacent to existing pavement that will be removed by a subsequent overlapping milling operation need not be removed. Vertical cuts in the roadway shall not be left overnight.
406.05 Mixing. When commencing recycling operations, the recycling agent shall be
applied to the pulverized material at the initial design rate determined by the Materials Laboratory, based on samples obtained by the Department before construction. The exact application rate of the recycling agent will be determined and may be varied as required by existing pavement conditions. An allowable tolerance of plus or minus 0.2 percent of the initial design rate or directed rate of applicat ion shall be maintained at all times. A representative of the recycling agent supplier shall be present on the project during recycling operations until an acceptable production sequence is established as determined by the Engineer. The Contractor may add water to the pulverized material to facilitate uniform mixing with the recycling agent. Water may be added before or concurrently with the recycling agent, provided that this water does not adversely affect the recycling agent.
406.06 Spreading. Recycling and placing recycled material shall be at a rate sufficient to
provide continuous operation of the paving machine. If paving operations result in being excessively behind or in excessive stopping of the paving machine, as determined by the Engineer, recycling operations shall be suspended. Recycling may resume when the Contractor can synchronize the rate of recycling with the capacity of the paving machine. If segregation occurs behind the paver , the Contractor shall make changes in equipment, operations, or both to eliminate the segregation.
406.07 Compacting and Finishing. After the recycled material has been spread, traffic,
including Contractor’s equipment, shall not be allowed on the recycled material until it starts its initial break as determined by the Engineer. However, if precipitation is imminent, compaction may proceed to seal the surface from additional moisture. Initial rolling shall be performed with one or more pneumatic tire rollers and be continued until no displacement is observed. Final rolling to eliminate pneumatic tire marks and achieve the required density shall be done by steel wheel rollers either in static or vibratory mode. The use of vibratory rollers shall be approved by the Engineer. If rollers are used in the vibratory mode, vibration shall be at low amplitudes to prevent transverse cracks. The recycled material shall be compacted to a minimum of 100 percent of the density of a laboratory specimen compacted per CP 53. If the area tested fails to meet the required density, the area shall be reworked until it attains 100 percent compaction. The frequency of density testing for project acceptance will be one per 5 ,000 square yards. The Engineer will perform one CP 53 for calculation of the percent relative compaction with each field density taken. Rollers shall not be started or stopped on uncompacted recycled material. Rolling shall be accomplished so that starting and stopping will be on previously compacted cold recycled pavement or existing pavement. Any type of rolling resulting in cracking, movement, or other types of pavement distress shall be discontinued until the problem is resolved. 406.08 406-3 After the recycled material has been compacted, traffic, including the Contractor’s equipment, shall not be permitted on the cold recycled pavement for at least two hours, unless otherwise approved. Before placing the sealing emulsion or hot mix asphalt overlay, the cold recycled pavement shall be allowed to cure until the free moisture is reduced to 1 percent free moisture or less, by total weight of mix. Free moisture will be measured according to CP 57. After the free moisture content of the cold recycled pavement has reached the acceptable level, the hot mix asphalt overlay or sealing emulsion, if required, shall be placed. However , unless otherwise approved by the Engineer, the cold recycled pavement shall be covered with a minimum thickness of 2 inches of hot mix asphalt within10 calendar days after it is laid and compacted. The sealing emulsion, if required, shall be applied to the surface at an approximate rate of 0.025 to 0.10 gallons per square yard. The sealing emulsion shall be applied when the Engineer determines that it is necessary to prevent raveling (prog ressive separation of aggregate particles). Damage caused by the Contractor to the cold recycled pavement shall be repaired at Contractor’s expense, as directed, before placing any hot asphalt surfacing. Soft areas that are not caused by the Contractor or weather shall also be repaired before placing the hot mix asphalt.
406.08 Recycling Train . The Contractor shall furnish a self -propelled machine capable of
pulverizing the existing asphalt surfacing to the depth shown on the plans, in one pass. The machine shall have a minimum rotor cutting width of 12 feet. The rotor cutting width selected for the project shall allow for the longitudinal joint to be offset from the longitudinal joint of the layer placed above by at least 6 inches. The longitudinal joint shall not fall in the wheel path. The machine shall have standard automatic depth contr ols and maintain a constant cutting depth. The machine shall also have screening and crushing capabilities to reduce or remove oversize particles before mixing with recycling agent. Oversize particles shall be reduced to size by crushing. The machine shall perform continuous weight measurement of the pulverized material interlocked with the recycling agent metering device so the required recycling agent content will be maintained. Positive means shall be provided for calibrating the weight measurement device and the recycling agent metering device. A positive displacement pump, capable of accurately metering the required quantity of recycling agent at rates as low as 4 gallons per minute, shall be used to apply the recycling agent. The interlock system shall allow addition of the recycling agent onl y when pulverized material is present in the mixing chamber. Each mixing machine shall be equipped with a meter capable of registering the rate of flow and the total amount of recycling agent introduced into the mixed material. The recycling agent shall be applied through a separate mixing machine capable of mixing the pulverized material and the recycling agent to a homogeneous mixture and placing the mixture in a windrow. The mixture shall be placed in a windrow in a manner that prevents segregation.
406.09 Paver. The recycled material shall be placed with a self -propelled asphalt paver
meeting the requirements of subsection 401.10, except that the screed shall not be heated. The mixed material shall be spread in one continuous pass, without segregation, to the lines and grades established on the plans. 406.10 406-4 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 to the underlying materials.
406.10 Compactors. Rollers shall be steel wheel, pneumatic tire, vibratory or combination
of these types. The number and weight of rollers shall be sufficient to obtain the required compaction while the recycled material is in a workable condition, except that each pneumatic tire roller shall be 30 tons’ minimum weight.
406.11 Smoothness. The longitudinal surface smoothness of the roadway before and after
cold recycling shall be tested by the Contractor per subsection 105.07. METHOD OF MEASUREMENT
406.12 In-place cold recycled pavement will be measured by the square yard of paved
surface actually recycled, complete in place and accepted. Repair of cold recycled pavement will be measured by the square yard of paved surface repaired and accepted. BASIS OF PAYMENT
406.13 The accepted quantity of in- place cold recycled pavement will be paid for at the
contract unit price per square yard. Payment will be made under: Pay Item Pay Unit Cold Asphalt Pavement (Recycle) Square Yard Repair of Cold Asphalt Pavement (Recycle) Square Yard Asphalt materials will be measured and paid for per Section 411. Water will not be measured and paid for separately but shall be included in the work. Repair of cold recycled pavement damaged by the Contractor or by weather will not be measured and paid for separately but shall be included in the work. Overlaps of preceding recycling operations will not be measured and paid for separately but shall be included in the work. 407.01 407-1 SECTION 407 PRIME COAT , TACK COAT , AND REJUVENATING AGENT DESCRIPTION
407.01 This work consists of preparing and treating an existing surface with asphalt material,
and blotter material if req uired, per these specifications and in conformity with the lines shown on the plans or established. MATERIALS
407.02 Asphalt Material. The type and grade of asphalt material for prime and tack coating
will be specified in the Contract. The asphalt material for all coatings shall meet the applicable requirements of Section 702. The asphalt material for prime and tack coating may be conditionally accepted at the source. The rejuvenating agent shall be accepted before loading into the distributor.
407.03 Blotter Material . Blotter material for prime coating shall consist of aggregate base
course conforming to the requirements specified for base course aggregate on the project. Blotter material for rejuvenating agent shall consist of dry, gritty sand conforming to the fine aggregate gradation of Table 703 -2, or as approved. Blotter material may be accepted in the stockpile at the source or at the roadway before placement. CONSTRUCTION REQUIREMENTS
407.04 Weather Limitations. Prime coat and tack coat shall not be applied under the
following conditions:
1.When the surface is wet.
2.When weather conditions would prevent the proper construction of the prime or tack coat.
407.05 Equipment. The Contractor shall provide equipment for heating and uniformly
applying asphalt material and blotter material. The distributor and equipment shall be capable of uniformly distributing asphalt material at even temperature and uniform pressure on variable widths of surface up to 15 feet at readily determined and controlled rates from 0.05 to 2.0 gallons per square ya rd. The allowable variation from any specified rate shall not exceed plus or minus 0.02 gallon per square yard. Distributor equipment shall include a tachometer, pressure gauges, accurate volume measuring devices or a calibrated tank, and a thermometer for measuring temperatures of tank contents. Distributors shall be equipped with a power unit for the pump and full circulation spray bars adjustable laterally and vertically. The distributor for rejuvenating agent shall also be equipped with the following:
1.Heating facilities with controls to reach a temperature of 130 °F .
2.Circulating system to maintain proper mixture of the rejuvenating agent.
Source: Colorado Standard Specifications for Road and Bridge Construction, 2023 Edition. Pages 365–368 of 943.