4-56 Section 413 – Hot In -Place Recycling
413.01 DESCRIPTION . This work shall consist of hot in -place recycling (HIR) of the existing pavement surface, including heating the pavement surface using specialized equipment causing the asphalt to soften, scarifying the softened pavement surface in a continuous process to the depth specified in the Plans, mixing the scarified asphalt pavement with a recycling agent that rejuvenates the asphalt, and placing and compacting the mix back onto the roadway. Excess recycled material not used in the HIR process will become the property and responsibility of the Contractor. 413.02 MATERIALS . Materials shall meet the requirements of the following subsections: Hot Recycling Agents ................................ ................................ ................................ 702.05 The HIR mixture shall be free of any materials not generally considered to be asphalt pavement. 413.03 EQUIPMENT .
a.General Requirements . The recycling equipment shall be capable of milling the existing roadway, sizing the resulting RAP, and mixing th e RAP with the recycling agent and any additives stipulated in the mix design. The equipment used shall be capable of placing the recycled pavement mixture to the requirements provided herein and to the lines and grades shown on the Plans. Any additional equipment used by the Contract or beyond th at specified below shall be approved by the E ngineer based on its suitability to produce results meeting the specification requirements.
b.Heating Unit . The heating unit shall generate sufficient heat to soften the asphalt pavement to the depth required. Care shall be taken not to overheat the existing pavement thereby softening the underlying asphalt pavement not to be scarified. The burner assembly shall be adjustable to heat between 8 feet and 14 feet i n width. The entire heating unit shall be enclosed and vented to contain the heat and prevent damage to adjacent properties and landscape. In cooler temperatures, an additional heating unit may be required.
c.Heater Scarification Train . This equipment sh all be a self -contained machine designed to reprocess only the upper layers of the existing pavement. The heater scarification train shall be self -propelled and capable of operating at speeds of 16 feet to 50 feet per minute while uniformly heating and scarifying the existing pavement to a minimum depth of one inch. Listed below are the various units that are part of the heater scarification train.
4-57 (1) Scarifying Unit . The scarifying unit shall contain at least two rows of spring -loaded tines
that are a djustable in one inch increments to scarify a width of 14 feet. This unit shall also be able to conform to the pavement contours to ensure a uniform penetration from the tines and prevent damage to utility structures.
2.Spray Unit . A rejuvenator shall be applied to the material during the scarifying process. The size of the nozzles located on the spray bar and pump shall be selected based upon the rate of application rate and the forward speed of the heater scarification unit. The spray unit shall be equi pped with an electronic digital measuring system, which shall be capable of maintaining the required application rate of the recycling agent with a tolerance of ± 5% for the mix design. The electronic digital measuring system shall continuously verify and display the application rate of recycling agent and cumulative total with respect to the volume of scarified material for the road surface. The Contractor shall calibrate the electronic digital measuring system in the presence of th e Engineer. Approved calibrations shall be done for each project. Work shall not progress until the calibration has been completed and verified.
d.Remixer Unit . Immediately following the application of the rejuvenating agent, the Contractor shall thoroug hly mix the agent with the scarified material to the required depth. This process may be completed with the use of a dual drum enclosed auger or mill head in a manner to perform proper and continuous blending. The remixer unit shall be an integral part of the scarifying machine and shall be located between the spray unit, which applies the recycling agent, and the screed. This unit shall be operated hydraulically, able to work at variable speeds from 0 rpm to 120 rpm, and shall be adjustable from 8 feet to 14 feet wide. In addition, this unit shall be able to break in the center to allow for quarter point and crown control.
e.Screed Unit . The hot scarified material shall be uniformly distributed to the desired longitudinal and transverse section by the use of an attached heated, augured vibratory screed. T he temperature of the hot scarified material shall be maintained between a minimum of 275°F and a maximum of 330°F. The screed shall be equipped with an adjustable crown control and each end of the screed shall have hand wheel adjusting screws for providing the desired longitudinal grade and transverse slope.
4-58 (f) Rollers . Rollers shall be in good mechanical condition, capable of reversing without backlash, and
operated at speeds slow enough to avoid d isplacement of the bituminous mixture. The weight of the rollers shall be sufficient to compact the mixture to the required density without crushing the aggregate. Rollers shall be equipped with tanks and spray bars for wetting the rolls or tires. Pneumat ic-tired rollers shall be equipped with appropriate skirts at all times and be preheated prior to use in order to avoid picking. The Contractor shall remove all picked material from the surface. Vibratory rollers shall have separate controls for energy an d propulsion. They shall be equipped with automatic cutoffs that stop the vibration prior to the roller stopping or reversing its direction of travel. 413.04 CONSTRUCTION REQUIREMENTS .
a.General Requirements . Agency personnel and equipment shall be allo wed free and full access to the project site at no additional compensation due the Contractor to allow for any and all sampling required to assess compliance with the provisions of this specification. The Contractor shall afford the Agency all traffic cont rol operations and provide means to extract samples as requested to achieve this effort. The recycling agent content used in production may vary throughout the project and be adjusted by the Contractor based on the results of QC testing or other variables with the approval of the Engineer, to maintain an optimized finished product.
b.Design Criteria . The HIR shall increase the average penetration value of the mixture by at least 30% over the original penetration, while not exceeding 100 microns, when te sted in accordance with AASHTO T 49 .
c.Mix Design . The Contractor shall develop an HIR mix design consisting of RAP and hot recycling agent. To obtain material to conduct mix designing, the Contractor shall sample exi sting pavement to represent the recycled aggregates. A minimum of six core samples representative of the project shall be taken . The Contractor shall develop and submit a material sampling plan for review and approval by the Agency a minimum of 5 working da ys prior to obtaining HIR mix design samples. At a minimum, the sampling plan shall include the number of samples, location of samples, and the method of sampling and backfilling. The mix design process shall include recovery of the asphalt binder from the RAP for penetration testing, dosing with recycling agent, and testing to determine the percent improvement of penetration. The mix design shall provide the type and recommended d osage rate of the recycling agent.
4-59 (d) Cleaning . The existing pavement and shoulder to be recycled shall be cleaned by using mechanical
sweepers, hand brooms, or other effective means until the surface is free of all material which might interfere with the scarification process.
e.Heater Scarification . The heating unit shall be operated in such a manner as to prevent damage to adjacent property and vegetation. All heat -damaged areas shall be repaired immediately to the satisfaction of the Engineer and at no additional cost to the Agency. The speed of the equipment shall be controlled to ensure that the recycled pavement is properly mixed, and uniformly distributed to the proper thickness, slope, and crown shown in the Plans. Extra care shall be taken i n controlling heater scarification equipment to prevent segregation of the recycled mix at the start and end of paving production as well as at any locations where the heater scarification train needs to stop and restart. The hot in -place pavement shall b e constructed to conform to the depth requirements and tolerances shown in the Plans. The width of each pass shall be controlled to provide proper placement of longitudinal joints, including a 3 inch overlap onto adjacent lane passes. Recycling agent shal l be added uniformly to the scarified pavement at the predetermined application rate to produce a homogenous recycled mix. The temperature of the scarified mixture shall be maintained between 275°F and 330°F prior to initial compaction. In areas having c atch basins or manholes that are not accessible to scarifying equipment, the Engineer will determine if they require repair. Pavement surfaces that are in good condition and are less than one square yard in size do not require repair. Areas that are greate r than one square yard in size or with cracks or spalls shall be repaired with bituminous concrete pavement, as approved by the Engineer.
f.Compaction . The CIR shall be compacted to 98% to 102% of the target maximum density (TMD). If two out of three co nsecutive density test results are outside of the allowable range, the Contractor will be required to construct a new test section to establish an updated TMD. If the Engineer determines that the TMD is apparently incorrect, as evidenced by being achiev ed with little or minimal compactive effort, then the Engineer will require a new test section to establish a new TMD.
4-60 (g) Surface Tolerance . The surface will be tested by the Engineer using a straightedge at least 12 feet
in length at selected locati ons parallel with the centerline. Any variations exceeding 1/8 inch between any two contact points shall be eliminated. A straightedge at least 10 feet in length may be used on a vertical curve. The straightedges shall be provided by the Contractor in acco rdance with Subsection 631.0 4.
h.Curing and Stability . The HIR may be opened to traffic after achieving the target density and after the material is determined to be stable by the Engineer. The required density shall be achieved and maintained until a wearing course pavement has been placed. Any additional compaction effort or repair of imperfections in the HIR material shall be performed as directed by the Engineer at no additional cost to t he Agency.
i.Weather and Seasonal Limitations . Hot in-place activities shall only be performed between the dates of May 16th and October 15th, inclusive. In addition, hot in-place activities shall only occur when the following conditions are met:
1.The atmospheric and road surface temperature, as measured by a thermometer placed in the shade at the recycling location, is at least 50°F and rising.
2.There is no standing water on the surface to be recycled. 413.05 QUALITY CONTROL .
a.General Require ments . The Contractor shall be responsible for performing all process control and quality control sampling and testing and operate in accordance with an approved QC plan. Prior to performing any HIR production, the Engineer or the Contractor may request a pre -recycle conference to discuss the recycling schedule. The Contractor shall sample, test, and evaluate the HIR process in accordance with the procedures and minimum frequencies specified in Table 413.05A .
4-61 Table 413.05a – Minimum Quality Control Frequencies
Test or Action Frequency Test Method Density 1 per 1,000 feet per lane AASHTO T 355 or AASHTO T 343 Air temperature 4 per day at even intervals Verified thermometer Surface temperature At beginning and end of each day ’s operation Verified thermometer Yield of recycling agent 2 per day at even intervals Tank check Penetration of recovered binder of mix 1 per mile per lane AASHTO T 49 Density testing shall be the average of three points across the lane (transverse) for each testing location. Quality control records shall include all sampling events, testing events, and process changes with accurate time and location data. The Contracto r shall submit QC records and summaries to the Engineer by 1:00 p.m. on the next working day. The Contractor shall make all test results, including randomly sampled densities, available to the Engineer onsite and on request. The Contractor shall cease rec ycling operations whenever one of the following occurs:
1.The submitted QC plan is not followed.
2.Density between 98% to 102% of TMD is not being achieved following corrective action.
3.The finished product is visually defective.
4.The computed rejuvenator yield differs from the mix design value by more than 10%.
5.The QC penetration values are less than 30% greater than the average original penetration values in the mix design.
6.The QC penetration values exceed 100 microns.
7.The recycled layer depth varies more than 1/4 inch across the width of the mat when checked behind the screed prior to compaction. Recycling operations shall not resume until the Contactor and the Agency agree on the corrective action to be taken.
4-62 (b) Qual ity Control Plan . The Contractor shall submit a quality control plan (QC plan) to the Engineer
a minimum of 14 calendar days prior to initiating HIR operations and shall not commence HIR operations until the QC plan is accepted by the Engineer. The QC plan shall address any items that affect the quality of the recycling process including, but not limited to, the following:
1.QC Plan Administrator . The QC plan administrator shall be identified in the QC Plan and shall list their past experience on HIR projects. They shall:
a.Be a full -time employee of the Contractor or an independent consultant not involved with the acceptance activities of the project .
b.Have a minimum of four years of experience in quality control activities in construction o perations .
c.Have full authority to institute actions necessary for successful implementation of the QC Plan.
2.Quality Control Technician . The quality control technicians (QCT) shall be responsible for conducting quality control and inspection activities to implement the QC plan. There may be more than one QCT on a project. They shall:
a.Be a full -time employee of the Contractor or an independent consultant with a minimum of two years of experience in quality control activities in field construction operations .
b.Have completed the requirements for the applicable testing by the Northeast Transportation Training and Certification Program (NETTCP) for Soils and Aggregate Inspector , or an equivalent regional program .
c.Have full authority to institute actions necessary for successful implementation of the QC Plan.
3.Recycling Supervisor . The recycling supervisor shall be responsible for conducting controlling the recycling proces s, quality control and inspection activities to implement the QC plan. They shall:
4-63 a. Be a full -time employee of the Contractor or an independent consultant with a
minimum of two years of experience in quality control activities in field construction o perations .
b.Have full authority to institute actions necessary for successful implementation of the QC plan.
4.Minimum Quality Control Parameters . Minimum quality control parameters are:
a.Make and type of all hot in-place equipment to be used on the project.
b.Description of heating system (radiant or direct burner) , including the heating equivalency.
c.The mixing system, including any drum speeds, operation, time, type, spacing, and configuration.
d.Project specific hot in-place mix design.
e.Proposed method for reducing or eliminating damage to adjacent property and landscape.
f.Make and type of rollers, including weight, weight per inch of drum, and average contact pressure for pneumatic tired rollers.
g.Proposed roller patterns to achieve den sity.
h.Density testing plan.
i.Recycling operations, including recycling speed and methods to ensure that the required treatment depth is obtained and that segregation is minimized.
j.Methods for protecting the finished product from damage and procedur es for any necessary corrective action or repair.
k.Methods of grade checks.
l.Examples of quality control forms.
m.Confirmation that all testing will be performed in accordance with AASHTO or other applicable procedures.
4-64 (c) Control Section . Control sections shall be con structed to establish the TMD at the beginning of the
HIR, and through the project as needed. The Contractor shall construct a control section to assure the Engineer that the Contractor’s equipment and procedures are suitable for the work specified and establish the target maximum density. The rolling pattern shall be determined from buildup, when the density readings show an increase in dry density of less than 1 pcf for the final four roller passes of each roller. The averag e of a minimum of 10 tests taken throughout the control section after the buildup is complete shall be used to determine the TMD. If Agency personnel are available, their values shall be included in the average, or used to establish the density gauge offse ts, as directed by the Engineer. The control section shall be full lane width and a minimum of 500 feet long, or as approved by the Engineer. No further recycling shall be performed until all aspects of the control section and the TMD are approved by the Engineer. The Contractor shall use the same equipment for building both the accepted test sections and performing the HIR work on the project unless equipment substitution is approved by the Engineer. The Engineer may require an additional test section and additional process control sampling to investigate the suitability of substituted or changed equipment. If the control section does not meet the requirements of this specification, or the target density is not determined from buildup testing, then the Con tractor shall modify the procedure and either construct another test section or reconstruct the original test section until suitable results are obtained. The Contractor shall provide the Engineer with written copies of all process control and quality control results from the control section by 1:00 p.m. on the next working day, including test locations. The Contractor shall make all test results available to the Engineer onsite and on request. 413.06 METHOD OF MEASUREMENT . The quantity of Hot In -Place Rec ycling to be measured for payment will be the number of square yards of existing pavement which has been recycled in an acceptable manner as determined by actual surface measurements of the lengths and widths of the recycled area as shown on the Plans or a s directed by the Engineer. No additional compensation will be made for overlapping areas. Areas where the scarifying equipment cannot be used and that are repaired with bituminous concrete pavement, such as catch basins or manholes, will be measured for payment as square yards of Hot In - Place Recycling.
4-65 413.07 BASIS OF PAYMENT. The accepted quantity of Hot In -Place Recycling will be paid for at the
Contract unit price per square yard. Payment will be full compensation for cleaning debris from the exist ing pavement; providing the recycling agent; heating and scarifying, mixing, paving, compacting, coring, and testing the recycled materials; and for furnishing all labor, tools, equipment, and incidentals necessary to complete the work. Furnishing and inco rporating the recycling agent will not be paid for separately but will be included in the unit price bid for Hot -In-Place Recycling. Payment will be made under: Pay Item Pay Unit 413.0100 Hot In -Place Recycling ................................ ................................ ............. Square Yard
4-66 Section 414 – Cold In -Place Recycling
414.01 DESCRIPTION . This work shall consist of cold in -place recycling (CIR) of the existing pavement surface, including milling bituminous pavement from the existing roadway, crushing or screening the existing bituminous pavement if needed, the addition of asphalt emulsion or foamed asphalt binder, Portland cement, and virgin aggregate, and mixing and repaving of the material to the depths, lines, and grades shown on the Plans. Excess recycled material not used in the CIR process will become the property and responsibility of the Contractor. 414.02 MATERIALS . Materials shall meet the requirements of the following subsections: Portland Cement ................................ ................................ ................................ ......... 701.02 Performance -Graded Asphalt Binder ................................ ................................ ......... 702.01 Anionic Emulsified Asphalt ................................ ................................ ....................... 702.02(a) Cationic Emulsified Asphalt ................................ ................................ ...................... 702.02(b) Aggregate f or Bituminous Concrete Mixtures ................................ ........................... 704.10 Recycled Asphalt Pavement ................................ ................................ ...................... 704.22(a) Water ................................ ................................ ................................ .......................... 745.01 Emulsified asphalt for CIR, when used, shall be type HFMS -2, HFMS -2h, HFMS -2s, CSS -1, CSS -1h, MS-2h, or as recommended by the Contractor as a result of the design criteria of this specification and approved by the Engineer. Foamed asphalt binder for CIR, w hen used, shall be unmodified and grade 58S -28, unless otherwise specified in the Contract. The CIR shall meet the gradation requirements of Table 414.02A for extracted aggregate ( AASHTO T 30 , dry) taken from the pulverized material. TABLE 414.02A – EXTRAC TED AGGREGATE GRADATION Sieve Designation Percentage by Mass (Weight) Passing Square Mesh Sieves 1-1/2 inch (37.5 mm) 100 1 inch (25.0 mm) 90 – 100 No. 4 (4.75 mm) 30 – 70 No. 200 ( 0.075 mm) 0 – 12
Source: Vermont Standard Specifications for Construction, 2024 Edition. Pages 374–383 of 1,380.