401.01 401-1 DIVISION 400 PAVEMENTS PLANT MIX PAVEMENTS –GENERAL DESCRIPTION
401.01 These specifications include general requirements that are applicable to all types of
hot mix asphalts irrespective of gradation of aggregate, kind and quantity of asphalt cement , or pavement use. Deviations from these general requirements will be indicated in the specific requirements for each type. This work consists of one or more courses of asphalt mixture constructed on a prepared foundation per these specifications and the specific requirements of the type under contract, and in conformity with the lines, grades , thicknesses, and typical cross sections shown on the plans or established. MATERIALS
401.02 Composition of Mixtures . The asphalt plant mix shall be composed of a mixture of
aggregate, filler or additives if required and approved, asphalt cement, and reclaimed material if permitted and used.
a.Mix Design . The Contractor shall submit the following to the Engineer:
1.A proposed hot mix asphalt mix design prepared per Colorado Procedure 52, including a proposed job -mix gradation for each mixture required by the Contract , which shall be wholly within the Master Range Table in subsection 703.04 before the tolerances shown in Section 401 are applied. The weight of lime shall be included in the total weight of the material passing the 75 µ m (No. 200) sieve.
2.The name of the refinery supplying the asphalt cement and the source of the anti- stripping additive.
3.A sufficient quantity of each aggregate for the Department to perform the tests specified in Section 3.2.1 of CP 52. The Contractor’s proposed job -mix formula for each hot mix asphalt grading will be tested by the Department utilizing materials actually produced and stockpiled for use on the project. The job -mix formula for each mixture shall establish a single percentage of aggregate passing each required sieve size, a single percentage of asphalt cement to be added to the aggregate, and a single temperature for the mixture at the discharge point of t he plant. When Laboratory tests indicate that a proposed job- mix formula complies with the specifications as revised for the project, a Form 43 shall be executed between the Engineer and the Contractor to establish the job -mix formula. After the Form 43 is executed, and all materials are available on the project, the Contractor shall notify the Engineer a minimum of one working day in advance of beginning production of the hot mix asphalt. Any changes in the Form 43 will require the same notification unless otherwise approved by the E ngineer. 401.02 401-2 (b) Mixtures Furnished to the Project. After the job -mix formula is established, all mixtures furnished for the project shall conform thereto within the ranges of tolerances listed in Table 401- 1. Table 401 -1 *TOLERANCES FOR HOT MIX ASPHALT *Hot Mix Asphalt – Item 403, Gradations #Passing the 9.5 mm ( 3/8 inch) and larger sieves ± 6% #Passing the 4.75 mm (No. 4) and 2.36 mm (No. 8) sieves ± 5% #Passing the 600 µm (No. 30) sieve ± 4% #Passing the 75 µm (No. 200) sieve ± 2% Asphalt Content ± 0.3% Asphalt Recycling Agent ± 0.2% Table 401 -1 Notes: * When 100% passing is designated, there shall be no tolerance. When 90 – 100% passing is designated, 90% shall be the minimum; no tolerance shall be used. #These tolerances apply to the Contractor’s Process Control Testing. The job -mix formula for each mixture shall be in effect unless modified in writing on Form 43. Should a change in sources of materials be made, a new job -mix formula shall be established before the new material is used. This new job -mix formula shall be in effect until modified by the Engineer. Requests made in writing by the Contractor for changes in the job -mix formula will be considered. The job -mix formula may be changed by the Engineer if the change will produce a mixture of equal or better quality and will:
1.Permit better utilization of available material, or
2.Result in a saving in cost to the Department through an adjustment in unit price. Tests for cleanliness, abrasion loss, and percent of fractured faces will be made on representative samples of aggregate taken during production or from the stockpiles. Hot mix asphalt (HMA ) will be tested for moisture susceptibility by the Department per Table 401- 2. If a sample fails to meet the criteria shown in Table 401 -2, the Contractor shall take corrective action before being permitted to continue production. If proper corrective action cannot be readily determined, the Engineer will suspend the us e of such material until Laboratory tests indicate that the corrective measures taken by the Contractor will provide material that is in compliance. If one or more samples fail to meet the requirements of Table 401 -2, material from the area represented by the failing sample will be evaluated as follows: If the area represented by the failing sample contains 2 ,000 tons of the new pavement or less, then the result for the failing sample shall be considered a lot of one and will be evaluated according to the formulas and procedures in subsection 105.03. 401.03 401-3 If the area represented by the failing sample contains more than 2 ,000 tons of the new pavement, then the material from the area represented by the failing sample will be sampled and tested according to the following method: Pavement samples for possible moisture susceptibility testing will be taken at a minimum frequency of once every 2 ,000 tons throughout the project. The Engineer will observe the sampling, take possession of the samples, and retain these samples for possible testing. Sample size shall be a minimum of 20 pounds. If a 10,000 -ton sample fails, then the four 2,000- ton samples from the area represented by that failing 10,000- ton sample will be tested for moisture susceptibility. The 10,000 -ton result and the fo ur 2,000- ton results will be considered a lot of five and will be evaluated according to the formulas and procedures in subsection 105.03. If less than four retained samples are on hand because the 10,000 -ton sample represents less than 8 ,000 tons of hot mix asphalt, the price adjustment will be based on the test results from the retained samples on hand plus the test result from the 10,000- ton sample. For the above evaluation, the “F” factor used in calculating P factors shall be 2.5. The P value shall be applied to price of the HMA item. If asphalt cement is not paid for separately, the price reduction shall be multiplied by 0.60. Lottman P values will not be combined with Pay Factors for other elements determined per Process Control/Owner Acceptance (PC/OA) specifications. Table 401 -2 HMA MOISTURE SUSCEPTIBILITY TEST FREQUENCY/CRITERIA Grading Test Procedure Minimum Test Result Sampling Frequency All Gradings CP L-5109 Method B 70 One per 10,000 tons or fraction (minimum)
401.03 Aggregates. Aggregates shall meet the applicable requirements of subsection 703.04.
401.04 Mineral Filler. Mineral filler shall meet the requirements of subsection 703.06.
401.05 Hydrated Lime. Hydrated lime shall meet the requirements of subsection 712.03.
401.06 Asphalt Cement s. The type and grade of asphalt cement will be specified in the
Contract. The asphalt cement shall meet the applicable requirements of Section 702. CONSTRUCTION REQUIREMENTS
401.07 Weather Limitations and Placement Temperatures . Hot mix asphalt shall be placed
only on properly prepared unfrozen surfaces that are free of water, snow, and ice. The hot mix asphalt shall be placed only when both the air and surface temperatures equal or exceed the temperatures specified in Table 401 -3 and the Engineer determines that the weather conditions permit the pavement to be properly placed and compacted. 401.08 401-4 Table 401 -3 PLACEMENT TEMPERATURE LIMITATIONS IN °F Compacted Layer Thickness in inches Minimum Surface and Air Temperature ºF Top Layer Minimum Surface and Air Temperature ºF Layers Below Top Layer < 1 1/2 60 50 1 1/2 - < 3 50 40 3 or more 45 35 Table 401 -3 Notes: Air temperature is taken in the shade. Surface is defined as the existing base on that the new pavement is to be placed. If the temperature falls below the minimum air or surface temperatures, paving shall stop. The Contractor shall schedule the work so that no planed or recycled surface is left without resurfacing for more than 10 calendar days during the period specified in Table 401 -4, below. The Contractor shall immediately place a temporary hot mix asphalt layer on any surface that has been planed or recycled and cannot be resurfaced per the above temperature requirements within 10 calendar days after being planed or recycled. The minimum thickness of the temporary hot mix asphalt layer shall be 2 inches. The Contractor shall perform the process control required to assure adequat e quality of the hot mix asphalt used in the temporary layer. All applicable pavement markings shall be applied to the temporary layer surface. The Contractor shall maintain the temporary layer for the entire period that it is open to traffic. Distress that affects the ride, safety, or serviceability of the temporary layer shall be immediately corrected to the satisfaction of the Engineer. The temporary hot mix asphalt layer shall be removed when work resumes. Table 401 -4 PERIODS REQUIRING OVERLAY OF TREATED SURFACES Location by Elevation Period That Planned or Recycled Surfaces Must be Overlaid within 10 Days All areas below and including 7000 feet October 1 to March 1 All areas above 7000 feet up to and including 8500 feet September 5 to April 1 All areas above 8500 feet August 20 to May 15
401.08 Asphalt Mixing Plant . The asphalt mixing plant shall be capable of producing a
uniform material, have adequate capacity, and be maintained in good mechanical condition. Defective parts shall be replaced or repaired immediately if they adversely affect the proper functioning of the plant or plant units, or adversely affect the quality of the hot asphalt plant mix. 401.09 401-5 Dust, smoke, or other contaminants shall be controlled at the plant site to meet all air quality requirements per subsections 107.01 and 107.24. Acceptable safety equipment shall be provided by the Contractor to accommodate sampling and testing. Hot asphalt plant mix shall not be stored longer than nine hours, unless additional protective measures are used and approved. When hot asphalt plant mix is obtained from a commercial plant, the Contractor shall make arrangements for approved laboratory facilities at the plant site for testing hot asphalt paving mixtures. The plant laboratory shall meet the requirements of subsect ion.
401.09 Hauling Equipment. Trucks used for hauling asphalt mixtures shall have tight, clean,
smooth metal beds thinly coated with a minimum amount of paraffin oil, lime solution, or other approved release agent. Petroleum distillates such as kerosene or fuel oil will not be permitted. Each truck shall have a cover of canvas or other suitable mater ial to protect the mixture from the weather.
401.10 Asphalt Paver s. Self-propelled asphalt pavers shall be provided and equipped with an
activated screed assembly, heated , if necessary, capable of spreading and finishing the asphalt plant mix material in lane widths applicable to the typical section and thicknesses shown in the Contract. Pavers used for shoulders and similar construction shall be capable of spreading and finishing courses of asphalt plant mix material in widths shown in the Contract. The paver’s receiving hopper shall have sufficient capacity for a uniform spreading operation and shall have an automatic distribution system that will place the mixture uniformly in front of the screed. The screed or strike- off assembly shall produce the specified finished surface without tearing, shoving, or gouging the mixture. The paver shall include an approved longitudinal paver wedge system to create a sloped SafetyEdge SM as shown on the plans. The wedge system shall be attached to the screed and shall compact the HMA to a density at least as dense as the compaction imparted to the rest of the HMA layer by the paving screed. The system shall provide a sloped SafetyEdge SM equal to 32 degrees plus or minus 5 degrees measured from the pavement surface cross slope extended. A single plate strike off shall not be used. The system shall be adjustable to accommodate varying paving thicknesses. The Engineer may allow the Contractor to use handwork for short sections or to saw cut the sloped SafetyEdge SM after paving operations are completed in areas such as transitions at driveways, intersections, interchanges. The Contractor shall submit the proposed paver wedge system for approval at the Pre-construction Conference. The Engineer may require proof that the system has been used on previous projects with acceptable results or may require a test section constructed before the beginning of work to demonstrate that it creates an acceptable wedge shape and compaction. Paving shall not begin until the system is approved in writing by the Engineer. The SafetyEdge SM may be constructed on each lift of HMA or on the full -specified plan depth on the final lift. The finished shape of the SafetyEdge SM shall extend for the full depth of the asphalt pavement or for the top 5 inches whichever is less. 401.10 401-6 The paver shall be capable of operating at forward speeds consistent with uniform and continuous laying of the mixture. Stop and go operations of the paver shall be avoided. The asphalt paver shall be equipped with a means of preventing the segregation of the coarse aggregate particles from the remainder of the asphalt plant mix when that mix is carried from the paver hopper back to the paver augers. The means and methods used shall be approved by the paver manufacturer and may consist of chain curtains, deflector plates, or other such devices and any combination of these. The following specific requirements shall apply to the identified asphalt pavers :
1.Blaw-Knox asphalt pavers shall be equipped with the Blaw -Knox Materials Management Kit (MMK).
2.Cedarapids asphalt pavers shall be those that were manufactured in 1989 or later.
3.Caterpillar asphalt pavers shall be equipped with deflector plates as identified in the December 2000 Service Magazine entitled “New Asphalt Deflector Kit {6630, 6631, 6640}”. Before the start of using the paver for placing plant mix, the Contractor shall submit for approval a full description in writing of the means and methodologies that will be used to prevent asphalt paver segregation. Use of the paver shall not commence before receiving approval from the Engineer. The Contractor shall supply a Certificate of Compliance that verifies that the approved means and methods used to prevent asphalt paver segregation have been implemented on all pavers used on the project. Pavers shall be equipped with automatic screed controls with sensors capable of sensing grade from an outside reference line and maintaining the screed at the specified longitudinal grade and transverse slope. The sensor shall be constructed to operate from either or both sides of the paver and shall be capable of working with the following devices:
1.Ski-type device at least 30 feet in length.
2.Short ski or short shoe.
3.At least 5,000 feet of control line and stakes. The type or types of devices to be furnished shall be as provided in the Contract. The controls shall be capable of maintaining the screed at the specified transverse slope within plus or minus 0.1 percent. Manual operation will be permitted for constructing irregularly shaped and minor areas. If the automatic controls fail or malfunction the equipment may be operated manually for the remainder of the normal working day, provided specified results are obtained. If the Contractor fails to obtain and maintain the specified surface tolerances, the paving operations shall be suspended until satisfactory corrections, repairs, or equipment replacements are made. Placement of hot mix asphalt on a waterproofed bridge deck shall be accomplished with equipment that will not damage the membrane or protective covering. 401.11 401-7 401.11 Tack Coat . When ordered by the Engineer or specified in the Contract, a tack coat shall be applied between pavement courses and paid for per Section 407.
401.12 Surface Conditioning . Irregularities in the existing pavement or base shall be brought
to uniform grade and cross section. Before placing tack coat and beginning overlay work, the surface to be tack coated shall be swept to remove accumulations of loose gravel and debris. Asphalt plant mix shall be placed only on properly constructed surfaces that are free from substances that would adversely affect the pavement quality. Contact surfaces of curbing, gutters, manholes, and other structures shall be painted with a uniform coating of asphalt cement before placing asphalt mixture against them.
401.13 Preparation of Asphalt Cement . The asphalt cement shall be heated to the specified
temperature without local overheating and shall be continuously supplied to the mixer at a uniform temperature within the specified range.
401.14 Preparation of Aggregates . Heating and drying of the aggregates shall be
accomplished without damaging the aggregate. When hydrated lime is used it shall be added to the aggregate per one of the following methods:
a.Lime Slurry Added to Aggregate. The hydrated lime shall be added to the aggregate in the form of a slurry and then thoroughly mixed in an approved pugmill. The slurry shall contain a minimum of 70 percent water by weight.
b.Dry Lime Added to Wet Aggregate. The dry hydrated lime shall be added to the blended aggregate wetted a minimum of 2 percent above the surface saturated dry condition (SSD) as shown on the Form 43, and then thoroughly mixed in an approved pugmill. The Engineer will not require the Contrac tor to increase the moisture above 5 percent total, although the Contractor may elect to do so if the added water is necessary to meet the minimum Lottman specification (See Table 401 -2). The Contractor may request that the 2 percent above SSD requirement be waived, provided the requirements of CPL 5150 have been met. If the HMA fails to meet the minimum TSR requirements defined in Table 401 -2 at any point during production, the Contractor shall immediately be required to add the minimum amount of moisture as defined above. The lime- aggregate mixture may be fed directly into the hot plant after mixing or it may be stockpiled for not more than 90 days before introduction into the plant for mixing with the asphalt cement. The hydrated lime may be added to different sized aggregates and stockpiled, by adding 75 percent of the lime to the aggregate passing the 4.75 mm (No. 4) sieve and 25 perc ent to the aggregate retained on the 4.75 mm (No. 4) sieve. In order to ensure the required lime and water quantities are introduced, lime and water feed for lime operation shall have control systems that change introduction rates in conjunction with changes in plant mix production. The control systems shall be do cumented in the Contractor’s PC Plan. When a test for aggregate percent moisture falls below the required minimum, the Contractor will receive a warning. When two consecutive tests for aggregate percent 401.15 401-8 moisture fall below the required minimum, a follow up test will immediately be performed. A failure on the follow up test will result in suspension of work. Production will remain suspended until the source of the problem is identified and corrected. Each time production is suspended, corrective actions shall be proposed in writing by the Contractor and approved in writing by the Engineer before production may resume.
401.15 Mixing . The dried aggregates and asphalt shall be combined in the mixer in the
quantities required to meet the job -mix formula. The materials shall be mixed until the aggregate is completely and uniformly coated, and the asphalt is uniformly distributed throughout the aggregate. The minimum temperature of the mixture when discharged from the mixer and when delivered for use shall be as shown in Table 401 -5: Table 401 -5 HMA MINIMUM DISCHARGE/DELIVERY TEMPERATURES Asphalt Grade Minimum Mix Discharge Temperature, ºF * Minimum Delivered Mix Temperature, ºF# PG 58- 28 275 235 PG 64- 22 290 235 PG 76- 28 320 280 PG 64- 28 320 280 PG 70- 28 320 280 PG 58- 34 300 280 Table 401 -5 Notes: *The maximum mix discharge temperature shall not exceed the minimum discharge temperature by more than 30 ºF. # Delivered mix temperature shall be measured behind the paver screed. Hot mix asphalt mixture shall be produced at the lowest temperature within the specified temperature range that produces a workable mix and provides for uniform coating of aggregates (95 percent minimum per AASHTO T 195), and that allows the required compaction to be achieved. Storing or holding of asphalt mixture will be permitted provided the characteristics of the mixture are not altered. If storing or holding of the mixture causes segregation, excessive heat loss, or adversely affects the quality of the finished product, corrective action shall be taken. Unsuitable mixture shall be disposed of at the Contractor’s expense. When placing hot asphalt mixture over bridge decks covered by waterproofing membrane, the minimum temperature of the mixture when rolling operations begin shall be 250 ºF . The job-mix formula temperature may be increased up to 30 ºF to obtain this temperat ure.
401.16 Spreading and Finishing . Asphalt pavers shall be used to distribute the mixture to
the established grade and required thickness over the entire width or partial width as practicable. 401.16 401-9 The longitudinal joint in both a new pavement and an overlay pavement layer shall offset the joint in the layer immediately below by 6 inches. In every pavement layer, the longitudinal joints shall not be constructed in the wheel paths . The Contractor shall submit a longitudinal joint and pavement marking plan three days before the Pre -paving Conference. The plan shall show the location and configuration of the proposed longitudinal joints and pavement markings and shall detail the methods to be used to field establish a control line. The Contractor shall use a continuous string line to delineate every longitudinal joint during paving operations. All exposed string line shall be picked up and disposed of at the en d of each day’s pavin g. Paving shall not commence until the plan has been approved in writing by the Engineer. The joints in the top layer of pavement shall be located as follows unless otherwise approved in writing by the Engineer:
1.For 2 -lane roadways, offset 6 to 12 inches from the center of pavement and from the outside edge of travel lanes.
2.For roadways of more than 2 lanes, offset 6 to 12 inches from lane lines and outside edge of travel lanes. Longitudinal joints shall not cross the centerline, lane line, or edge line unless approved by the Engineer. Where paving operations are on the present traveled roadway, the Contractor shall arrange paving operations so there will be no exposed longitudinal joints between adjacent travel lanes at the end of a day’s run. With the approval of the Engineer, the Contractor may leave an exposed longitudinal joint conforming to the following:
1.When the thickness of the pavement course being placed is 1.5 inches or less a vertical exposed longitudinal joint may be constructed.
2.When the thickness of the pavement course being placed is greater than 1.5 inches the joint shall be constructed according to one of the following:
A.The entire joint shall be tapered 3:1 or flatter. A Taper steeper than 3:1 shall be considered vertical.
B.The top portion of the longitudinal joint may be vertical. The vertical portion shall be a maximum of 1.5 vertical inches. The remainder of the joint, below the vertical portion, shall be tapered 3:1 or flatter. On areas where the use of mechanical spreading and finishing equipment is impracticable, the mixture shall be dumped, spread, raked, screeded, and luted by hand tools to the required compacted thickness and grades. Production of the mixture shall be maintained so pavers can be used in echelon to place the wearing course in adjacent lanes. The asphalt mixture shall be transported and placed on the roadway without segregation. All segregated areas behind the paver shall be removed immediately upon discovery. The segregated material shall be replaced with specification material before the init ial rolling has taken place. If more than 50 square feet of segregated pavement is ordered removed and replaced in any continuous 500 linear feet of paver width laydown, operations shall be discontinued until the source of the segregation has been found an d corrected. If at any time, the Engineer observes segregated areas of pavement, they will notify the Contractor immediately. 401.16 401-10 After rolling, segregated areas will be delineated by the Engineer and evaluated as follows:
1.The Engineer will delineate the segregated areas to be evaluated and inform the Contractor of the location and extent of these areas within two calendar days, excluding weekends and holidays, of placement.
2.In each segregated area or group of areas to be evaluated, the Contractor shall take five 10 -inch cores at random locations designated by the Engineer. Per CP 75, the Contractor shall also take five 10 -inch cores at random locations designated by the Engineer in non -segregated pavement adjacent to the segregated area. These cores shall be within 30 feet of the boundary of the segregated area and in the newly placed pavement. The coring shall be in the presence of the Engineer and the Engineer will take immediate possession of the cores. The Contractor may take additional cores at the Contractor’s expense.
3.Gradation of the aggregate of the cores will be determined by CDOT per CP 46.
4.The core aggregate gradations from the segregated area will be compared to the core aggregate gradations of the corresponding non -segregated area.
5.Two key sieves of the core gradations from the segregated area will be compared to the core gradations from the corresponding non -segregated area to determine the difference. If differences for both key sieves exceed the allowable difference specified in the table below, the area is segregated. Table 401 -6 SEGREGATION DETERMINATION Mix Grading Key Sieves Allowable Difference, % SX 2.36 mm (#8), 4.75 mm (#4) 9 S 2.36 mm (#8), 4.75 mm (#4) 9
6.Segregated areas in the top lift shall be removed and replaced, full lane width, at the Contractor’s expense. The Engineer may approve a method equivalent to removal and replacement that results in a non- segregated top lift. Segregated areas, in lifts be low the top lift that are smaller than 50 square feet per 100 linear feet of lane width shall be corrected by the Contractor at the Contractor’s expense in a manner acceptable to the Engineer. Segregated areas larger than 50 square feet per 100 linear feet of lane width in any lift shall be removed and replaced, full lane width, by the Contractor at the Contractor’s expense. If the area is determined to be segregated, the coring shall be at the expense of the Contractor. If the area is determined to be non -segregated, the Engineer will reimburse the Contractor $2,000 for obtaining the 10 cores. The Engineer will perform a systematic segregation check per CP 58 as early in the project as is feasible to determine if temperature segregation problems exist. Temperature segregation will be of concern on the project if, across the width of the mat, temperatures vary by 25 °F or more. Densities will not need t o be taken in the systematic segregation check. The Engineer will discuss the temperature findings of the systematic segregation check with the Contractor. 401.17 401-11 The Engineer may evaluate the HMA for low density due to temperature segregation whenever industry best practices, as detailed on Form 1346, are not being followed or the Engineer suspects temperature segregation is occurring. The Engineer will first meet with the Contractor to discuss the paving practices that are triggering the temperature investigation. Areas across the mat, excluding the outside 1 foot of both edges of the mat, that are more than 25 °F cooler than other material across the width may b e marked for density testing. Material for temperature comparison will be evaluated in 3 - foot intervals behind the paver across the width of the mat. The material shall be marked and tested per CP 58. If four or more areas within a lot of 500 tons have densities of less than 93 percent of the material’s maximum specific gravity for SMA mixes or less than 92 percent of the material’s maximum specific gravity for all other HMA mixes, a 5 percent price disincentive will be applied to the 500- ton lot. The 5 00-ton count begins when the Engineer starts looking for cold areas, not when the first cold area is detected. This price disincentive will be in addition to those described in Sections 105 and 106. Only one area per delivered truck will be counted towar d the number of low - density areas. Temperature segregation checks will be performed only in areas where continuous paving is possible.
401.17 Compaction . The hot mix asphalt shall be compacted by rolling. Both steel wheel and
pneumatic tire rollers will be required. The number, weight, and type of rollers furnished shall be sufficient to obtain the required density while the mixture is in a workable condition. Compaction shall begin immediately after the mixture is placed and be continuous u ntil the required density is obtained. When the mixture contains unmodified asphalt cement (PG 58- 28 or PG 64- 22) or modified (PG 58- 34), and the surface temperature falls below 185 °F , further compaction effort shall not be applied unless approved, provided the Contractor can demonstrate that there is no damage to the finished mat. If the mixture contains modified asphalt cement (PG 76- 28, PG 70- 28 or PG 64 -28) and the surface temperature falls below 230 °F , further compaction effort shall not be applied unless approved, provided the Contractor can demonstrate that there is no damage to the finished mat. Warm Mix Asphalt compaction requirements shall conform to CP 59. All roller marks shall be removed with the finish rolling. Use of vibratory rollers with the vibrator on will not be permitted during surface course final rolling and will not be permitted on any rolling on bridge decks covered with waterproofing membrane . SMA shall be compacted to a density of 93 to 97 percent of the daily theoretical maximum specific gravity, determined according to CP 51. All other HMA shall be compacted to a density of 92 to 96 percent of the daily theoretical maximum specific gravity, d etermined according to CP 51. If more than one theoretical maximum specific gravity test is taken in a day, the average of the theoretical maximum specific gravity results will be used to determine the percent compaction. Field density determinations wil l be made per CP 44 or 81. The longitudinal joints shall be compacted to a target density of 92 percent of the theoretical maximum specific gravity. The tolerance shall be plus or minus 4 percent. The theoretical maximum specific gravity used to determine the joint density will be the average of the daily theoretical maximum specific gravities for the material that was placed on either side of the joint. Density (percent relative compa ction) will be determined per CP 44. 401.17 401-12 The Contractor shall obtain one 6 -inch diameter core at a random location within each longitudinal joint sampling section for determination of the joint density. The Contractor shall mark and drill the cores at the location directed by the Engineer and in the presence of the Engineer. The Engineer will take possession of the cores for testing. The Contractor may take additional cores at his own expense. Coring locations shall be centered on the visible line where the joint between the two adjacent lifts abuts the surface. The center of all joint cores shall be within 1 inch of this visible joint line. Core holes shall be repaired by the Contractor using materials and methods approved by the Engineer. PC and OA joint coring shall be completed within five calendar days of joint construction. Longitudinal joint coring applies to all pavement layers. When constructing joints in an echelon paving process, the joints shall be clearly marked to ensure consistent coring location. In small areas, such as intersections, where the Engineer prescribes p aving and phasing methods, the Engineer may temporarily waive the requirement for joint density testing. Incentive or disincentive payment determined for joint density per subsection 105.05 will apply to the HMA on each side of the joint. If a layer of pavement has joints constructed on both sides, incentive or disincentive payment for each of those joints will apply to one half of the pavement between the joints. Along forms, curbs, headers, walls, and all other places not accessible to the rollers, the mixture shall be thoroughly compacted with mechanical tampers. Any mixture that becomes loose and broken, mixed with dirt, or is in any way defective, shall be immediately removed and replaced with fresh hot mixture, and compacted to conform to the surrounding area. The Contractor shall construct a compaction pavement test section (CTS) for each job mix where 2,000 or more tons are required for the project. The CTS will be used to evaluate the number of rollers and the most effective combination of rollers and rolling patterns for achieving the specified densities. Factors to be considered include, but are not limited to, the following:
1.Number, size, and type of rollers.
2.Amplitude, frequency, size and speed of vibratory rollers.
3.Size, speed, and tire pressure of rubber tire rollers.
4.Temperature of mixture being compacted.
5.Roller patterns. The CTS shall be constructed according to the following procedures: The CTS shall be constructed to provide the nominal layer thickness specified. The first 500 tons of hot mix asphalt on the project location shall constitute the CTS. The production and placement rates of the CTS shall closely approximate the anticipated production and placement rates for the remainder of the Contract. Compaction of the CTS shall commence immediately after the hot mix asphalt has been spread and shall be continuous and uniform over the entire CTS. For the CTS, compaction shall continue until no discernible increase in density is obtained by additional compactive efforts. All compaction shall be completed before the surface temperature of the mixture drops below 185 °F . 401.17 401-13 Approved types of rollers shall be used to achieve the specified density. The Contractor shall determine what methods and procedures are to be used for the compaction operation. The compaction methods and procedures shall be used uniformly over the entir e last 200 tons. The Contractor shall record the following information and a copy of this data shall be furnished to the Engineer.
1.Type, size, amplitude, frequency, and speed of roller.
2.Tire pressure for rubber tire rollers, and whether the pass for vibratory rollers is vibratory or static.
3.Surface temperature of mixture behind the laydown machine and subsequent temperatures and densities after each roller pass.
4.Sequence and distance from laydown machine for each roller, and number of passes of each roller to obtain specified density. Two sets of random cores shall be taken within the last 200 tons of the CTS. Each set shall consist of seven random cores. The Engineer will determine the coring locations using a stratified random sampling process. The locations of these cores will be such that one set can serve as a duplicate of the other. One set of these cores shall be immediately submitted to the Engineer. This set will be used for determining acceptance of the CTS and determining density correction factors for nuclear density equ ipment. Densities of the random samples will be determined by cores according to CP 44. Density correction factors for nuclear density equipment will be determined according to CP 81. Coring shall be performed under CDOT observation. Coring will not be measured and paid for separately but shall be included in the work. For SMA, a CTS is not used. The Contractor shall follow the requirements for the demonstration control strip per the Revision of Section 403, Stone Matrix Asphalt Pavement . The CTS meets requirements if the Quality Level of the random samples is greater than or equal to 75. The Quality Level will be determined according to CP 71. Once constructed and accepted, the CTS shall remain in place and become part of the hot mix asphalt on the project. When the Quality level is less than 75 the Contractor shall construct an additional test section, utilizing different rollers, or roller positions, or roller patterns as required. A written proposal detailing the changes in methods and procedures that wil l be used to obtain density is to be submitted to the Engineer for review before constructing the additional test section. If the Quality Level of a CTS is less than 75 and greater than or equal to 44, the Engineer may accept the material at a reduced price per Section 105. 401.18 401-14 If the Quality Level of a CTS is less than 44, the Engineer may:
1.Require complete removal and replacement with specification material at the Contractor’s expense.
2.Where the finished product is found to be capable of performing the intended purpose and the value of the finished product is not affected, as determined by the Engineer, permit the Contractor to leave the material in place with a pay factor, but not more than 75 percent of the bid price. Each CTS shall be 500 tons. If in -place densities of the CTS, as determined by nuclear density equipment before determining density of the cores, meet the CTS density requirements, the Contractor may begin production paving and continue to place hot mix asphalt pavement under the following conditions:
1.The period during which the Contractor continues to pave without test results from cores shall not exceed one workday .
2.Construction proceeds at the Contractor's risk. If correlation with the cores reveals that the densities do not meet the CTS requirements, the hot mix asphalt pavement placed subsequently will be subject to price reduction or removal and replacement. After production paving work has begun, a new Roller Pattern shall be demonstrated when a change in the compaction process is implemented. All additional costs associated with construction of the CTS shall be at the Contractor’s expense. The hot mix asphalt placed in the CTS will be paid for per subsection 401.22, at the contract price for the hot mix asphalt .
401.18 Joints . Placing of the hot mix asphalt shall be continuous, and rollers shall not pass
over the unprotected end of a freshly laid mixture. Transverse joints shall be formed by cutting back on the previous run to expose the full depth of the course. A coat of asphalt cement shall be applied to contact surfaces of all joints just before additi onal mixture is placed against the previously compacted material. Location and configuration of longitudinal joints shall be per subsection 401.16.
401.19 Pavement Samples . The Engineer may take samples of the compacted pavement at
random locations on the project for testing. Where samples have been taken, new material shall be placed and compacted by the Contractor to conform with the surrounding area.
401.20 Surface Smoothness . The roadway surface smoothness shall be tested per
subsection 105.07. METHOD OF MEASUREMENT
401.21 Hot mix asphalt and asphalt cement will be measured by the ton. Batch weights will
not be permitted as a method of measurement. The tonnage shall be the weight used in the accepted pavement. Deduction will not be made for the weight of asphalt cement in the mixture. 401.22 401-15 BASIS OF PAYMENT
401.22 All work performed and measured as described above will be paid for as provided in
the respective sections for each type specified. If there is no pay item for asphalt cement of the type specified it will not be measured and paid for separately but shall be included in the work. Water used in the mixing plant, per subsection 401.14, to bring the lime -aggregate mixture to approved moisture content will not be measured and paid for separately but shall be included in the work. Facilities for testing hot asphalt plant mix at the site of the commercial plant will not be paid for separately but shall be included in the work. When asphalt cement is a separate pay item, the amount of asphalt cement contained in reclaimed asphalt pavement (RAP) material will not be measured or paid for but shall be included in the work. Coring for in -place density, coring for longitudinal joint density, core hole repair, and associated expenses will not be paid for separately but shall be included in the work. Traffic control for this work will be paid for per the contract. All costs of the temporary hot mix asphalt layer required according to subsection 401.07, maintenance and removal of the temporary pavement layer, temporary pavement marking, and traffic control will not be paid for separately but shall be included in the work. All costs associated with the construction of the SafetyEdge SM specified in subsection 401.10 will not be paid for separately but shall be included in the work. 401.22 401-16 THIS PAGE INTENTIONALLY LEFT BLANK 403.01 403-1 SECTION 403 HOT MIX ASPHALT DESCRIPTION
403.01 This work consists of constructing one or more courses of hot mix asphalt (HMA ) on a
prepared base per these specifications, and in conformity with the lines, grades, thicknesses, and typical cross sections shown on the plans or established. The asphalt pavement shall be composed of a mixture of aggregate, filler if required, and asphalt cement. Hot Mix Asphalt (Patching) consists of those quantities required for the replacement of unstable corrugated areas in the existing pavement, pipe trenches, areas removed for curb and gutter forms, areas between the curb and gutter or sidewalk and the existing paved parking lots, and areas designated on the plans. These quantities will be restricted to small areas that require hand placement methods and where conventional paving equipment cannot be utilized. MATERIALS
403.02 The materials shall conform to the requirements of subsections 401.02 through 401.06.
CONSTRUCTION REQUIREMENTS
403.03 The construction requirements shall be as prescribed in subsections 401.07 through
401.20. Areas to be patched shall be excavated and squared to a neat line, leaving the sides of the excavation vertical. Before placement of the patch, the exposed sides of the existing pavement shall be thoroughly coated with emulsified asphalt (slow -setting). Hot mix asphalt shall then be placed and compacted in succeeding layers not to exceed 3 inches in depth. METHOD OF MEASUREMENT
403.04 Hot mix asphalt will be measured as prescribed in subsection 401.21.
BASIS OF PAYMENT
403.05 The accepted quantities of hot mix asphalt will be paid for per subsection 401.22, at
the contract unit price per ton for the asphalt mixture. Payment will be made under: Pay Item Pay Unit Hot Mix Asphalt (Grading ) Ton Hot Mix Asphalt (Grading ) (Asphalt) Ton Hot Mix Asphalt (Patching) (Asphalt) Ton
Source: Colorado Standard Specifications for Road and Bridge Construction, 2023 Edition. Pages 345–360 of 943.