S-12-0004 Attachment 1D NDOT Specs.pdf

NDOT

SPECIFICATIONS

The State of Nevada Standard Specifications for Road and Bridge Construction, US Standard Units (Inch Pound Units), Edition of 2001 applies on this project as a static Specification Book as well as all other applicable specification changes. A limited number of Division II NDOT specifications have been included with this submittal that directly apply to this project. Refer to the NDOT Standard Specification book if other referenced sections are not included herein.

The State of Nevada Standard Plans for Road and Bridge Construction, US Standard Units (Inch Pound Units), Edition of 2010 applies on this project as a static Drawing Book as well as all other applicable drawing changes.

Voids in Mineral Aggregate (Types 2 and 2C Plantmix Aggregate)

Indirect Tensile Strength (Retained Strength)

Indirect Tensile Strength (Unconditioned) (With AC-10 Asphalt)

Indirect Tensile Strength (Unconditioned) (Type 3 except with AC-10 Asphalt)

Indirect Tensile Strength (Unconditioned) (Types 2 and 2C except with AC-10 Asphalt)

Stabilometer Value (Type 3)

Stabilometer Value (Type 2C)

Stabilometer Value (Type 2)

Percent Air Voids of Compacted Bituminous Mixture (Types 2 and 3) (Premixed)

Percent Air Voids of Compacted Bituminous Mixture (Type 2C)

Percent Air Voids of Compacted Bituminous Mixture (Types 2 and 3)

TEST

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SECTION 401

PLANTMIX BITUMINOUS PAVEMENTS

GENERAL

DESCRIPTION

401.01.01 General. These specifications include general requirements that are applicable to all types of bituminous pavements of the plantmix type, irrespective of gradation of aggregate, kind and amount of bitumi-nous material, or pavement use. Deviations from these general requirements will be indicated in the specific requirement for each type.

This work consists of constructing one or more courses of bituminous mixture on the prepared foundation.

MATERIALS

401.02.01 General. Material shall conform to the following Sections and Subsection:

Bituminous Materials ...............................................................................................................Section 703 Aggregates for Bituminous Courses .............................................................................................Section 705 Commercial Mineral Filler ............................................................................................Subsection 705.03.03 Engineering Fabrics .................................................................................................................Section 731

401.02.02 Composition of Mixtures. Compose the bituminous plantmix of a mixture of aggregate, min-eral filler, and bituminous material. Size, uniformly grade, and combine the several aggregate fractions in such proportions that the resulting mixture meets the grading requirements of the job-mix formula.

Do not commence paving or coldmilling operations until the following requirements have been complied with:

(a) An approved mix design conforming to the requirements of this Subsection and Section 705 is received from the Department’s Materials Division.

Mix Design Requirements (Plantmix and Roadmix Bituminous Surface Aggregates):

TEST METHOD

30 Min.

REQUIREMENTS

AASHTO T269

AASHTO T269

AASHTO T269

Nev. T303

Nev. T303

Nev. T303

Nev. T341

Nev. T341

Nev. T341

Nev. T341

Nev. T338

70% Min.

12 to 22%

448 kPa (65 psi) Min.

400 kPa (58 psi) Min.

345 kPa (50 psi) Min.

35 Min.

37 Min.

6 to 9%

4 to 7%

3 to 6%

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401 PLANTMIX BITUMINOUS PAVEMENTS

In addition, the mixture design will be evaluated per Nevada Test Method No. Nev. T760. Mixture designs not meeting this requirement may be rejected.

(b) Based upon the approved mix design, submit a written proposed job-mix formula for use by the Engineer in setting the job-mix to be used. For metric unit contracts, provide the proposed job-mix formula in metric units or both metric and English units. For English unit contracts, provide the proposed job-mix formula in English units or both English and metric units. Identify the asphalt cement supplier in the job-mix formula. Include in the proposed formula definite single values for:

1. The percentage of aggregate passing each specified sieve.

2. The percentage of bitumen to be added (to 0.1%), by dry mass of aggregate.

3. The temperature of the mixture leaving the mixer.

4. The minimum temperature of the mixture in the hopper of the paving machine.

5. The percentage of each aggregate bin used. (Bin percentages of less than 5% will not be allowed.)

The job-mix formula with the allowable tolerances shown herein shall conform to Section 705.

A job-mix formula with single values for 1, 2, 3, 4, and 5 above will be determined and notification will be given in writing. This job-mix formula shall be in effect until modified in writing by the Engineer.

Furnish mixture conforming to the job-mix formula, within the following range of tolerances:

Aggregate passing the 4.75 mm (No. 4) and larger sieves .................................................................± 7% Aggregate passing the 2.36 mm to 150 µm (No. 8 to No. 100) sieves .................................................± 4% Aggregate passing the 75 µm (No. 200) sieve................................................................................± 2% Bitumen content......................................................................................± 0.4% dry mass of aggregate Temperature leaving the mixer......................................................................................± 11 °C (20 °F)

Job-mix formula (1) shall reflect the asphalt percentage recommended by the approved mix design.

Consistently produce a mixture with an asphalt content at the target value. Do not use the above opera-tional tolerance as a means to alter the asphalt content target value.

If the aggregates and asphalt cement submitted for a bituminous mix design produces a mixture exhibiting critical properties, see Note 1 below, be responsible for deciding whether a mixture can be produced which consistently meets project specification requirements, see Note 2 below.

If electing to use a mix design that yields a critical mix, proceed and place the three field trial mixture sec-tions to be subjected to testing.

If no satisfactory recommendation can be made by the Engineer from the test results of the trial sections, a new bituminous mix design will be required and a suspension of paving operations will be required until a new mix design is approved. Working days will continue to be charged.

If the test results are satisfactory, the paving may continue, however, the mixture will be monitored to assure that the project specification requirements are consistently met, see Note 2 below.

Note 1: A critical mixture is one where there is a narrow range in the bitumen ratio in which project specification requirements are met for Stabilometer Value and Percent Air Voids of Compacted Bituminous Mixture (being a single point value or values in the acceptable range that do not allow for a ±0.4% fluctuation from the target value in bitumen content and still meet Stabilometer Value and Percent Air Voids requirements). If the range in the bitumen ratio, where Stabilometer Value and Percent Air Voids specification requirements are met, is 0.7% or less, the mixture will be reported as “critical” and the above listed criteria shall be met before its use on the project.

Note 2: If two consecutive behind the paver samples (field samples) or 25% of the material sampled and tested, on a rolling 10 samples, fail to meet specification requirements for Stabilometer Value and/or Percent Air Voids, the paving operations will be shut down. Submit a plan outlining corrective measures to alleviate the failing material, and receive approval before any further paving. Working days will not be suspended during any such shutdown. (Rolling 10 samples indicates that only the preceding 10 samples will be counted in the analysis for consideration of failure, not the entire set of samples.)

On the first day of bituminous mix production, produce 3 trial mixtures of 450 metric tons (500 tons) of mix each. Complete production of the trial mixtures the same shift. Produce the trial mixtures at the medium speed used during the plant calibration. The trial mixtures may be placed on the shoulder of the roadway or the pass-ing lane of four lane roadways and become a section of the completed roadway. For other roadways place at an

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401PLANTMIX BITUMINOUS PAVEMENTS

approved location. Suspend production of the bituminous mix for a maximum of 3 working days or until all test results, except for Indirect Tensile Strength (Unconditioned) or Indirect Tensile Strength (Retained Strength), are available. Working days will not be charged during the 3 working day suspension. Production may com-mence without the results of the Indirect Tensile Strength (Unconditioned) or Indirect Tensile Strength (Retained Strength) tests.

Field Trial Mixture No. 1 shall conform to job-mix formula (1). Field Trial Mixture No. 2 shall conform to job-mix formula (1) except the asphalt content shall be +0.4%. Field Trial Mixture No. 3 shall conform to job-mix formula (1) except the asphalt content shall be –0.4%.

Acceptance of the plant produced trial mixtures will be based on test results meeting the requirements of this Subsection with the aggregate gradation within the job mix ranges given and the in-place densities meeting the requirements of Subsection 402.03.06.

When test results of the trial mixtures do not meet the requirements, additional plant trial mixtures may be required and the required tests performed during one additional maximum 3 working day suspension or a new mix design may be required.

Remove field trial mixtures not meeting all the requirements of the specifications from the roadway. One half the quantity of rejected trial mixtures will be paid for at the applicable unit bid prices. Also, one half of the removal quantity of rejected trial mixtures will be paid for at the applicable unit bid price or, when no removal item exists, according to Subsection 104.03. The other one half of the above quantities will not be paid for.

A revised job-mix formula (if applicable) will be provided based on the results of the tests performed on the field trial plant produced mixtures. The asphalt content will be selected, based on meeting the specifications for Hveem stability and percent air voids.

Should there be a change in sources of material, establish a new approved mix design and a new job-mix for-mula. When unsatisfactory results make it necessary, the Engineer may establish a new job-mix formula and give notification in writing.

The final plantmix product placed on the roadway shall comply with the approved mixture design, and the following project control requirements:

TEST METHOD

30 Min.

TEST REQUIREMENTS

Percent Air Voids of Compacted Bituminous Mixture (Types 2 and 3)

Percent Air Voids of Compacted Bituminous Mixture (Type 2C)

Percent Air Voids of Compacted Bituminous Mixture (Types 2 and 3)(Premixed)

Stabilometer Value (Type 2)

Stabilometer Value (Type 2C)

Stabilometer Value (Type 3)

Indirect Tensile Strength (Unconditioned) (Types 2 and 2C except with AC-10 Asphalt)

Indirect Tensile Strength (Unconditioned) (Type 3 except with AC-10 Asphalt)

Indirect Tensile Strength (Unconditioned) (With AC-10 Asphalt)

Indirect Tensile Strength (Retained Strength)

AASHTO T269

AASHTO T269

AASHTO T269

Nev. T303

Nev. T303

Nev. T303

Nev. T341

Nev. T341

Nev. T341

Nev. T341 70% Min.

448 kPa (65 psi) Min.

400 kPa (58 psi) Min.

345 kPa (50 psi) Min.

35 Min.

37 Min.

6 to 9%

4 to 7%

3 to 6%

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GRADE AND TYPE MC OR SC

BITUMINOUS MATERIAL AND MIXTURES

401 PLANTMIX BITUMINOUS PAVEMENTS

Cease production if, two consecutive test results or 40% of the total tests taken to date for the current tar-get percent mineral filler and target percent bitumen content, for Indirect Tensile Strength (Unconditioned) or Indirect Tensile Strength (Retained Strength) are below the required value. A change greater than or equal to 0.5% in the target percent mineral filler or target percent bitumen content or a new mix design is needed to restart the recording of the test results as stated above. Closely evaluate available information and determine the likely cause or causes of the problem, and take corrective action. Resume production when the results or other information satisfactorily indicate that the material to be produced will meet the specified values.

The temperature of the bituminous material just before mixing, and completed mixture in the hauling vehi-cle just before leaving the plant shall conform to the following tables:

PLANTMIX BITUMINOUS MIXTURES WITH ASPHALT CEMENT

BITUMINOUS MATERIAL

Minimum °C (°F)

Minimum °C (°F)

Minimum °C (°F)

Maximum °C (°F)

Maximum °C (°F)

Maximum °C (°F)

PLANTMIX OPEN–GRADED MIXTURESPLANTMIX SURFACE MIXTURES

GRADE OF

ASPHALT

CEMENT

AC-2.5

AC-5

AC-10

AC-20

AC-20P

AC-30

AC-40

121 (250) 135 (275) 135 (275) 135 (275) 149 (300) 135 (275) 135 (275)

163 (325) 177 (350) 177 (350) 177 (350) 177 (350) 177 (350) 177 (350)

104 (220) 118 (245) 124 (255) 129 (265) 143 (290) 132 (270) 135 (275)

163 (325) 177 (350) 177 (350) 177 (350) 177 (350) 177 (350) 177 (350)

104 (220) 118 (245) 124 (255) 129 (265) 143 (290) 132 (270) 135 (275)

135 (275) 135 (275) 143 (290) 143 (290) 163 (325) 143 (290) 143 (290)

The minimum temperature of the completed mixture at the hopper of the paver will be a single value deter-mined by the Engineer, which shall conform to the following table, but shall not be more than 11 °C (20 °F) lower than the temperature of the completed mixture leaving the plant, except for AC-20P Open-Graded mix-tures which shall not be more than 8 °C (15 °F) lower than the temperature of the completed mixture leaving the plant.

Minimum °C (°F)

Minimum °C (°F)

Maximum °C (°F)

Maximum °C (°F)

PLANTMIX BITUMINOUS OPEN–GRADED MIXTURESPLANTMIX BITUMINOUS SURFACE MIXTURES

GRADE OF

ASPHALT

CEMENT

AC-2.5

AC-5

AC-10

AC-20

AC-20P

AC-30

AC-40

93 (200) 107 (225) 113 (235) 118 (245) 141 (285) 121 (250) 124 (255)

163 (325) 177 (350) 177 (350) 177 (350) 177 (350) 177 (350) 177 (350)

93 (200) 107 (225) 113 (235) 118 (245) 141 (285) 121 (250) 124 (255)

135 (275) 135 (275) 143 (290) 143 (290) 163 (325) 143 (290) 143 (290)

PLANTMIX BITUMINOUS MIXTURES WITH LIQUID ASPHALT

Minimum °C (°F) Maximum °C (°F)

35 (95) 57 (135) 74 (165) 93 (200)

60 (140) 79 (175) 96 (205)

116 (240)

The temperature of the completed mixture (when using liquid asphalts) at the hopper of the paver shall not be more than 11 °C (20 °F) below the specified completed mixing temperature in the hauling vehicle just before leaving the plant.

The temperature of the completed mixture discharged from the mixer also shall not exceed the range speci-fied in the tables.

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Furnish five 3.75 L (1 gal), samples of each grade of asphalt cement specified in the contract not less than 20 working days before starting paving operations. Furnish samples for polymerized asphalt cements in paint can type containers.

Also furnish a sample of the aggregates not less than 20 working days before starting paving operations. Do not submit samples for bituminous mix designs until a minimum of 4,500 metric tons (5,000 tons) or 25% of the required contract quantity is produced proportionately in stockpile, whichever is less. Obtain samples from the produced stockpiles, or a composite of informational belt samples taken during the production of the min-imum quantity stated above, to represent each individual stockpile. The Engineer will obtain these samples or witness the Contractor obtaining them.

See Subsection 106.04.

Bituminous material may be conditionally accepted at the source.

In lieu of furnishing samples of asphalt cement and aggregates for a mixture design a mix design may be submitted which has been previously approved by the Department’s Materials Division.

A maximum of 1% of the material passing the 75 µm (No. 200) sieve may be removed from the combined aggregates submitted for the mix design to bring the combined gradation within specification.

If the submitted plantmix bituminous surface aggregate and asphalt cement meet the individual specification requirements, but fail to meet the mix design requirements when combined, a one time suspension of up to 10 working days may be allowed, when deemed necessary, for resubmittal and retesting for an acceptable mix design.

CONSTRUCTION

401.03.01 Bituminous Mixing Plant.

(a) General. Maintain the storage yard in a neat and orderly manner. Make stockpiles, readily accessible for sampling.

Store asphalt cement in tanks separate and apart from dryer burner fuel. Tanks with separate compartments may be used only if the compartments do not have a common wall. Provide viewing port between compart-ments.

(b) Burner Fuel and Burner. Limit fuel used for heating aggregates to the following types; natural gas, liqui-fied natural gas, fuel oil (ASTM D396, Grades No. 1 and No. 2), butane, propane, diesel fuel oil (ASTM D975, Grades No. 1-D and No. 2-D).

Certify that burner fuels comply with the foregoing and provide Certificate of Compliance conforming to Subsection 106.05.

The burner used for heating the aggregate shall achieve complete combustion of the approved fuel and not leave any fuel residue that will adhere to the heated aggregate.

(c) Mixing Plants. Use mixing plants conforming to the following:

1. Requirements for All Plants. Use mixing plants of sufficient capacity and coordinate to adequately han-dle the proposed bituminous construction. Provide 48 hours notice before beginning mixing plant cali-brations. For job-site plants, provide a copy of the current NDEP permit covering the limitations of the mixing plant production capacity not less than 48 hours before beginning calibrations.

a. Equipment for Preparation of Bituminous Material. Equip tanks for the storage of bituminous material to heat and hold the material at the required temperatures. Accomplish the heating by steam coils, elec-tricity, or other approved means so that no flame shall be in contact with the tank. Design the circulat-ing system for the bituminous material to assure proper and continuous circulation during the operating period. Make provision for measuring and sampling storage tanks.

b. Drier. Use a drier or driers which continuously agitate the aggregate during the heating and drying process.

c. Thermometric Equipment. Fix an armored thermometer of adequate range in temperature reading in the bituminous feed line at a suitable location near the charging valve at the mixer unit.

Replacement of any thermometer by an approved temperature-recording apparatus for better regulation of

[ 152 ] the temperature of aggregates may be required. Use thermometers that record in degrees Celsius (Fahrenheit for English unit contracts).

d. Smoke and Dust Control. Install satisfactory precipitation devices, or use other methods which will meet local conditions, city, county, and state laws pertinent to air pollution.

e. Truck Scales. Except as allowed in Subsection 401.04.01, provide approved platform or silo scales con-forming to Subsection 109.01.

f. Safety Requirements. Provide adequate and safe stairways to the mixer platform and sampling points and place guarded ladders to other plant units at all points where accessibility to plant operations is required. Provide access to the top of truck bodies by a platform to enable the Engineer to obtain sam-ples and mixture temperatures. Provide a hoist or pully system to raise scale calibration equipment, sam-pling equipment, and other similar equipment from the ground to the mixer platform and return.

Thoroughly guard and protect gears, pulleys, chains, sprockets, and other dangerous moving parts.

Maintain ample and unobstructed passage at all times in and around the truck loading areas. Keep this area free from drippings from the mixing platform.

g. Baghouse Fines. If introducing baghouse fines into the mix, draw the material from a storage facility in which the material is kept in a uniform free flowing condition. Supply the baghouse fines for deliv-ery to the plant from a positive weighing device which is interlocked, (rate of baghouse fines introduc-tion shall automatically vary with the rate of the aggregate feeder) to the flow of each aggregate feeder.

Equip the baghouse feeder to provide continuous uniform flow within 5% of the actual mass.

In a continuous mix and/or dryer drum plant add the baghouse fines at the asphalt feed line to insure a uniform mix.

In batch plants add the baghouse fines by the use of a separate bin.

Introduce the baghouse fines at an approved point, at a percentage determined by the Department’s Materials Division, and not exceeding 2% by dry mass of the aggregate.

Consider baghouse fines as part of the aggregate, and not as a mineral filler.

h. Controls. Do not operate mixing plants with manual controls when equipped with computer controls.

2. Requirements for Batching Plants.

a. Plant Scales. Provide scales accurate to 0.5% of the maximum load that may be required. Design poises to be locked in any position to prevent unauthorized change or position. In lieu of truck scales, an approved automatic printer system which will print the masses of the material delivered may be used, provided the system is used in conjunction with an approved automatic batching and mixing control sys-tem. Document such masses by a weigh ticket for each load.

b. Feeder for Drier. Provide the plant with accurate mechanical means for uniformly feeding the aggre-gate into the drier so that uniform production and uniform temperature will be obtained.

c. Screens. Use plant screens capable of screening all aggregates to the specified sizes and proportions when the aggregate is proportioned after the drying operations. Plant screens may be eliminated when proportioning is done before the drying process and the aggregate is proportioned according to subpara-graph 4. b., of this Subsection and prepared according to the first paragraph of Subsection 401.03.08.

d. Bins. Provide storage bins of sufficient capacity to supply the mixer when it is operating at full capac-ity. Arrange bins to assure separate and adequate storage of appropriate fractions of the mineral aggre-gates. Provide separate dry storage for mineral filler when used and equip the plant to feed such mater-ial into the mixer. Provide each bin with overflow pipes, of such size and at such locations as to prevent backing up of material into other compartments or bins. Provide each compartment with its own indi-vidual outlet gate, constructed to cut off quickly and completely. Construct bins so that samples can be readily obtained.

e. Weigh Box or Hopper. Include a means for accurately weighing each size of aggregate in a weigh box or hopper suspended on scales and of ample size to hold a full batch without hand raking or running over. The gate shall close tightly so that no material is allowed to leak into the mixer while a batch is being weighed.

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f. Bituminous Control Unit. Provide satisfactory means, either by weighing or metering, for obtaining the proper amount of bituminous material in the mix within the tolerance specified. Provide means for check-ing the quantity or rate of flow of bituminous material into the mixer.

g. Bituminous Control. Use equipment to measure the bituminous material accurately to ±0.5%. The bitu-minous material bucket shall be a nontilting type with a loose sheet metal cover. Use a discharge open-ing or spray bar with a length of not less than 75% of the length of the mixer and which discharges directly into the mixer. Adequately heat the bituminous material bucket, its discharge valve or valves, and spray bar. Efficiently drain steam jackets, if used, and construct connections so that they will not interfere with the efficient operation of the bituminous scales. Provide bituminous material bucket with a capacity of at least 15% in excess of the mass of bituminous material required in any batch. Provide adequately heated quick-acting, nondrip, charging valve located directly over the bituminous material bucket.

Measure bituminous material by means of springless dial scales or metering devices. Provide springless dial scales with a capacity of not more than 450 kg (1,000 lb) in 1 kg (2 lb) gradations.

Provide the indicator dial with a capacity of at least 15% in excess of the quantity of bituminous mate-rial used in a batch. Construct the controls so that they may be locked at any dial setting and will auto-matically reset to that reading after the addition of bituminous material to each batch. Place the dial in full view of the mixer operator. Automatically control the flow of bituminous material so that it will begin when the dry mixing period is over. Discharge all of the bituminous material required for one batch in not more than 15 seconds after the flow has started. Provide the size and spacing of the spray bar open-ings for a uniform application of bituminous material the full length of the mixer. Provide the section of the bituminous line between the charging valve and the spray bar with a valve and outlet for checking the meter when a metering device is substituted for a bituminous material bucket.

h. Mixer. Provide the batch mixer of a twin pugmill type, with steam jackets, or heat by other approved means and capable of producing uniform mixtures within the specified tolerances. Equip it with a suffi-cient number of paddles or blades set in proper order and operated at such speed as to produce a prop-erly and uniformly mixed batch. Do not exceed 25 mm (1 in.) clearance of the paddles or blades from all fixed and moving parts. Do not use badly worn or defective paddles or blades in mixing operations.

i. Control of Mixing Time. Equip the mixer with an accurate time lock to control the operations of a com-plete mixing cycle. The time lock shall lock the weigh box gate after the charging of the mixer until the closing of the mixer gate at the completion of the cycle. The time lock shall lock the bituminous mate-rial bucket throughout the dry mixing period and shall lock the mixer gates throughout the dry and wet mixing periods. The dry mixing period is defined as the interval of time between the opening of the weigh box gate and the start of introduction of bituminous material. The wet mixing period is the interval of the time between the start of introduction of bituminous material and the opening of the mixer gate.

Equip the mixer with a timing device which will indicate by a definite audible or visual signal the expi-ration of the mixing period. The device shall measure the time of mixing within an accuracy of 2 sec-onds. Provide and maintain a suitable automatic device in proper working condition for counting the num-ber of batches.

When the aggregates and the bituminous material have been combined, mix the entire mass in an approved mixer. Continue the mixing until a homogeneous mixture with a uniform coating is achieved.

Do not exceed output rate greater than the manufacturer’s capacity rating.

3. Requirements for Continuous Mixing Plants (Proportioned After Drying).

a. Feeder for Drier. Provide the plant with accurate mechanical means for uniformly feeding the aggre-gate into the drier so that uniform production and uniform temperature will be obtained.

b. Screens. Provide plant screens capable of screening all aggregates to the specified sizes and propor-tions.

c. Bins. Provide storage bins of sufficient capacity to supply the mixer when it is operating at full capacity. Arrange bins to assure separate and adequate storage of appropriate fractions of the mineral aggregates. Provide separate dry storage for mineral filler when used and equip the plant to feed such material into the mixer. Provide each bin with overflow pipes, of such size and at such locations as to prevent backing up of material into other compartments or bins. Provide each compartment with its indi-vidual outlet gate. Construct bins so that samples can be readily obtained. Equip bins with adequate tell-tale devices to indicate the position of the aggregates in the bins at the lower quarter points.

d. Aggregate Proportioning. Provide a means for accurately proportioning each size of aggregate after the drying operation.

Provide a mechanical feeder mounted under each compartment bin. Each compartment bin shall have an accurately controlled individual gate for volumetrically measuring the material drawn from each com-partment. The feeding orifice shall be rectangular with one dimension adjustable by positive means.

Provide indicators for each gate to show the respective gate opening.

Provide a meter for determining the rate of each feeder, or a revolution counter.

e. Mass Calibration of Aggregate. Provide a means for calibration of each aggregate feeder by weighing test samples. Provide accurate scales and test boxes for this mass calibration.

f. Bitumen Metering Device. Introduce the bituminous material into the mixer through a positive dis-placement metering device. Equip this metering device with a ready means of varying the bituminous material delivery rate.

g. Synchronization of Aggregate Feed and Bituminous Material Feed. Provide satisfactory means to afford a positive interlocking control between the flow of each feeder and the flow of bituminous material. The interlocking control shall indicate a visible or audible signal when the level of material in any one feeder approaches the strike off capacity of the feed gate, or shut the plant down.

h. Mixer. Include a continuous mixer of an approved type, adequately heated and capable of producing a uniform mixture within the job-mix tolerances. Use paddles adjustable for angular position on the shafts and reversible to retard the flow of the mix. The mixer shall have a manufacturer’s plate giving the net volumetric contents of the mixer at the several heights inscribed on a permanent gage. Provide charts showing the rate of feed of aggregate per minute for the aggregate being used.

i. Surge Bins. Equip the plant with an approved surge bin at the discharge. Provide surge bin in excess of 18 metric tons (20 tons), and equip with an approved surge batcher or other approved method that will prevent segregation of the bituminous mixture as it is being discharged into the hauling vehicle.

4. Requirements of Continuous Mixing Plants (Proportioned Before Drying).

a. Aggregate Stockpiles. The first paragraph of Subsection 401.03.08 shall apply.

b. Aggregate Proportioning. Include a means for accurately proportioning each size of aggregate before the drying operation. Separate each compartment bin by a vertical divider of adequate height to prevent aggregate spillover from adjacent bins. In addition, provide each bin with an accurate method of regu-lating and measuring the material being drawn from the bin. Provide indicators for each bin to show respective feed rates.

c. Mass Calibration of Aggregate. Calibrate plants after receiving an approved mix design. Calibrate the aggregate weigh belt at 3 different speeds, (lowest, medium, and the highest speed of anticipated opera-tion) using the bin percentages from the approved mix design with the assigned material in the bins.

Provide accurate platform scales in the same pit as the plant, and test boxes having a capacity of not less than 9 metric tons (10 tons) for this purpose. Calibrate plants before beginning the plantmix operation or whenever a plant is moved, and no less than once a year, or any other time directed. Calibrate the aggregate feed so the masses shown on the console indicators are within 1% of the actual mass as weighed on the sealed platform scales. The difference of the 3 runs will be within 1% of each other.

During production do not run outside the parameters of the plant calibration masses. Supply a graph of each individual bin showing the speed of the belt to the tons per hour of the material. The graph will be checked during the calibration and must be approved before production proceeds. This calibration pro-cedure will be observed and must be approved. Once the plant is calibrated and a minimum of 24 hours prior to beginning production, produce a quantity of bituminous mixture that shall provide a representa-tive sample to prove that the gradation and bitumen content of the mixture conform to the approved job-mix formula before beginning production.

d. Bitumen Metering Device and Calibration. Introduce the bituminous material into the mixer through a positive displacement metering device. Equip this metering device with a ready means of varying the bituminous delivery rate. Before beginning the plantmix operation, and at any other time directed, cali-brate the bitumen feed at 3 different speeds using the asphalt percentage set in the approved mix design

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[ 155 ] so the masses or liters (gallons) shown on the indicators are within 0.5% of the actual mass as weighed on the sealed platform scales. Use a vessel for calibration having a capacity of not less than 3,785 L (1,000 gal). Furnish the vessel and platform scales. This calibration procedure will be observed and must be approved.

e. Synchronization of Aggregate Feed and Bituminous Material Feed. Provide satisfactory means to afford a positive interlocking control between the flow of each feeder and the flow of bituminous material. The interlocking control shall indicate a visible or audible signal when the level of material in any one feeder approaches the strike off capacity of the feed gate, or shut the plant down.

f. Mixer. Include a continuous mixer of an approved type, adequately heated and capable of producing a uniform mixture within the job-mix tolerances. Use paddles adjustable for angular position on the shafts and reversible to retard the flow of the mix. Retard the flow of material through the mixer by reversing a minimum of the last two rows of paddles or providing a material dam. The mixer shall have a manu-facturer’s plate giving the net volumetric contents of the mixer at the several heights inscribed on a per-manent gage. Provide charts showing the rate of feed of aggregate per minute for the aggregate being used.

g. Surge Bins. Equip the plant with an approved surge bin at the discharge. Provide surge bin in excess of 18 metric tons (20 tons) capacity, and equip with an approved surge batcher or other approved method that will prevent segregation of the bituminous mixture as it is being discharged into the hauling vehicle.

5. Requirements for Dryer Drum Mixing Plants. The requirements of subparagraph 4 of this Subsection shall apply, with the exception of subparagraph 4. f.

a. Mixer. Include a mixing device which will obtain a homogeneous mixture with a uniform coating. The mixing output shall not exceed the manufacturer’s capacity rating.

401.03.02 Hauling Equipment. Use trucks for hauling bituminous mixture with tight, clean, and smooth metal beds which may be thinly coated with a minimum amount of one of the asphalt release agents listed in the QPL to prevent the mixture from adhering to the truck beds. Do not use diesel or kerosene.

Discharge the bituminous mixture from the surge-storage system directly into the hauling vehicle.

401.03.03 Pavers. Use pavers that are self contained, power-propelled units, provided with an activated screed or strike-off assembly, heated if necessary, and capable of spreading and finishing courses of bituminous mixture in lane and shoulder widths applicable to the specified typical section and thicknesses shown on the plans.

Equip pavers with a receiving hopper having sufficient capacity for a uniform spreading operation. Equip the hopper with a distribution system to place the mixture uniformly in front of the screed.

Equip the screed with automatic controls which will make adjustments in both transverse and longitudinal direction. The external longitudinal reference devices used to pick up grade information for the automatic sens-ing control shall conform to the following:

When picking up grade information from an underlying base, the external longitudinal reference device shall be a floating beam at least 9 m (30 ft) long or an 8 m (27 ft) non-contact averaging ski with a min-imum of 4 sensors.

When picking up grade information from an adjacent compacted pavement course or a concrete surface, the external longitudinal reference device shall be a floating beam or a non-contact averaging ski with a minimum of 2 sensors. Either referencing device shall be at least 3 m (10 ft) in length.

When using a floating beam to pick up grade information, place the sensing device in the middle third of the floating beam.

A non-contact sensor may be used to pick up grade information from a newly placed adjacent compacted course only when approved.

Should the automatic controls fail to function properly, finishing the half shift with manual controls may be approved. Do not resume until the controls are repaired.

401.03.04 Rollers. Rollers shall meet the following requirements:

(a) Breakdown rollers shall be a 2 axle tandem steel wheeled weighing not less than 9.1 metric tons (10 tons) and capable of rolling with or without vibration.

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(b) Pneumatic tired rollers shall weigh not less than 9.1 metric tons (10 tons) and be equipped with pneu-matic tires of equal size and diameter mounted on 2 axles attached to a rigid frame equipped with a load-ing platform or body suitable for ballast loading. The minimum width between the outer edge of the out-side tires on a given axle is 1.5 m (60 in.). Use tires with satisfactory treads. Space the tires on the rear axle so that the entire gap between adjacent tires on the front axle will be covered by the tread of the rear tires. Uniformly inflate the tires so that the air pressure in the tires will not vary more than 35 kPa (5 psi). Use the tire manufacturer’s recommended inflation pressure. Use a minimum tire size of 185 mm x 375 mm (7.5 in. x 15 in.), 4 ply. Fully skirt roller with rigid material to within 25 mm (1 in.) of the pavement surface.

(c) The finish roller shall be a 2 axle tandem steel wheeled weighing not less than 7.2 metric tons (8 tons).

401.03.05 Weather Limitations. Do not place plantmix bituminous surface when frozen materials are present in the base.

Do not place plantmix bituminous surface during rain or snowfall or when the roadway is wet.

Place plantmix bituminous surface when the atmospheric temperature is above those listed below:

Compacted Thickness Atmospheric Temperature Less than 25 mm (1 in.) ...............................................................................................13 °C (55 °F) 25 to 50 mm (1 to 2 in.) ................................................................................................7 °C (45 °F) Greater than 50 mm (2 in.) .............................................................................................2 °C (35 °F)

Place plantmix bituminous surface only when the surface temperature is above 10 °C (50 °F).

Place open-graded plantmix surface only when the atmospheric temperature and the pavement surface tem-perature are above 15 °C (60 °F).

401.03.06 Preparation of Existing Surface. When the surface of the existing pavement or old base is irregular, bring it to a uniform grade and cross section as directed.

Paint contact surface of curbing, gutters, manholes, and other structures with a thin, uniform coating of emul-sified asphalt before the bituminous mixture is placed.

401.03.07 Preparation of Bituminous Materials. Heat the bituminous material to the specified temper-ature in a manner that will avoid local overheating and provide a continuous supply of the bituminous material to the mixer at a uniform temperature at all times.

When polymer modified asphalt is specified, deliver and maintain the material in storage tanks at a mini-mum temperature of 149 °C (300 °F).

When polymer modified bituminous asphalt is placed in storage tanks, continuously circulate or moderately agitate them within the tanks.

401.03.08 Preparation of Aggregates. Separate aggregates proportioned before the heating and drying process, into two general sizes: (1) that portion of the material having a minimum of 80% passing a 4.75 mm (No. 4) sieve, and (2) that portion of the material having a minimum of 80% retained on a 4.75 mm (No. 4) sieve. Maintain the material within these limits with a uniformity of ± 5%. Store each portion of the material separately. When moving the aggregate from storage to compartment bins, use any method which will not cause segregation, degradation, or combinations of aggregate which fail to meet the specified gradation requirements.

Do not commence plantmix operations until a minimum of 4,500 metric tons (5,000 tons) combined has been proportionately stockpiled and marinated, unless the tonnage required is less than 4,500 metric tons (5,000 tons).

Screen aggregates proportioned immediately after the heating and drying process into a minimum of two frac-tions, if minus 12.5 mm (1/2 in.) aggregate is used, and into a minimum of three fractions when larger sized aggregate is used. Convey the screened material to separate compartments ready for proportioning, and mixing with bituminous material. Do not commence plantmix operations until a minimum of 4,500 metric tons (5,000 tons) has been proportionately stockpiled and marinated, unless the tonnage required is less than 4,500 metric tons (5,000 tons).

When the required tonnage is more than 4,500 metric tons (5,000 tons), then maintain a minimum of 4,500 metric tons (5,000 tons) of material proportionately stockpiled until such time as 4,500 metric tons (5,000 tons)

[ 157 ] or less are needed to complete the plantmix operations. Place the aggregates in the cold feed proportioning bins directly from the stockpile. Do not charge the cold feed bins from the crushing plant.

The plasticity index for any individual stockpile for use in the plantmix products before marination shall not exceed 10. Correct the plasticity problem if the plasticity index of any individual stockpile exceeds 10 before marinating the material. Do not blend with sand to lower the plasticity index.

Mineral Filler Feeding. Add mineral filler to all plantmix bituminous aggregates according to the Marination Method.

Marination Method. Wet cure the coarse aggregates with mineral filler at a minimum rate of 1% of the mass of dry aggregate. Wet cure the fine aggregates with mineral filler at a minimum rate of 2% of the mass of the dry aggregate. Marinate (wet cure) the aggregates in stockpiles for a minimum of 48 hours. Fine aggregate stockpiles have a minimum of 50% passing the 4.75 mm (No. 4) sieve. All other stockpiles will be treated as coarse aggregate. Marinate stockpiles individually. Do not use the marination method process to combine stock-piles.

Use the wet cured aggregate in the stockpile within 60 days.

Before the introduction of the mineral filler add sufficient moisture by way of spray bars at the aggregate bins to bring the aggregate to a moisture content where enough free surface moisture is available to thoroughly wet the aggregate and activate the lime. The actual amount of moisture shall be as approved. After the addition of water and mineral filler, mix the aggregate using a horizontal twin-shaft pugmill with a minimum effective mix-ing length of 1.5 m (5 ft). Use mixing paddles which are adjustable for angular position on the shaft to permit altering of the mixing pattern or retarding the flow to insure that the aggregate is thoroughly coated with min-eral filler. Do not extend the volume of material in the pugmill above the vertical position of the blade tips.

Retard the flow of material through the pugmill by reversing a minimum of the last two rows of paddles or pro-viding a material dam.

Draw mineral filler from a storage facility in which the mineral filler is agitated by air or other means to keep it in a uniform free flowing condition. Deliver the mineral filler to the mixer from a positive weighing device which is interlocked, (actuate electric driven feeders from the same circuit) to the flow of each aggre-gate feed. Equip the mineral filler feeder to provide a continuous uniform flow to within 5% of the required amount. Provide an aggregate feed and weight system which meets the requirements of Subsection 401.03.01.

Cold Feed Method. The Cold Feed Method is not allowed for use unless specifically stated in the Special Provisions. When the Cold Feed Method is allowed for use, add hydrated lime (hereinafter referred to as min-eral filler) to all plantmix bituminous aggregates at the rate of not less than 1% nor more than 2.5% of the mass of the dry aggregate. The exact rate of application shall be as approved.

Draw mineral filler from a storage facility in which the mineral filler is agitated by air or other means to keep it in a uniform free flowing condition. Deliver the mineral filler to the mixer from a positive weighing device which is interlocked, (actuate electric driven feeders from the same circuit) to the flow of each aggre-gate feeder. Equip the mineral filler feeder to provide continuous uniform flow to within 5% of the required amount.

In continuous mix and/or drum dryer plants, add the mineral filler to the aggregate after the aggregate is proportioned.

In batch plants, add the mineral filler to the aggregate before drying.

Before the introduction of the mineral filler add sufficient moisture by way of spray bars at the aggregate bins to bring the aggregate to a moisture content where enough free surface moisture is available to thoroughly wet the aggregate and activate the lime. The actual amount of moisture shall be as approved. After the addition of water and mineral filler, mix the aggregate using a horizontal twin-shaft pugmill with a minimum effective mix-ing length of 1.5 m (5 ft). Use mixing paddles which are adjustable for angular position on the shaft to permit altering of the mixing pattern or retarding the flow to insure that the aggregate is thoroughly coated with min-eral filler. Do not extend the volume of material in the pugmill above the vertical position of the blade tips.

Retard the flow of material through the pugmill by reversing a minimum of the last two rows of paddles or pro-viding a material dam. Directly introduce the completed mixture into the hot plant. Do not stockpile the com-pleted mixture.

Interlock the moisture control valve with the hot plant control room so the moisture control valve is auto-

[ 158 ] matically turned off when the cold feed belts are shut off. The control valve shall also turn on automatically when the cold feed belts are activated.

Baghouse Fine Feeding. Use the same type storage facility and feeding system for baghouse fines as used for mineral filler.

In batch plants, add the baghouse fines by the use of a separate bin.

In a continuous mix and/or a dryer drum plant, add the baghouse fines at or near the asphalt feed line.

401.03.09 Mixing. Do not exceed a moisture content of 1% in the bituminous mixture just behind the paver as determined by Test Methods No. Nev. T112 (Method A) or T306. Take satisfactory corrective action before resuming plantmix operations should the aggregate contain excessive moisture when heated within the temperature limits.

Combine the dried aggregate in the mixer in the amount of each fraction of aggregates required to meet the job-mix formula. Measure and gage the bituminous mixture and introduce into the mixer in the amount speci-fied by the job-mix formula.

When the aggregates and the bituminous material have been combined, mix the entire mass in an approved mixer. Continue mixing until homogeneity and a uniform coating are achieved. Do not exceed the manufac-turer’s capacity rating for the output rate.

Should the mixture at the discharge of the mixer, at the plant, in the haul vehicle, or in place, show a non-uniform or nonhomogeneous mix, show an excess or deficiency of bitumen, show injury or damage due to burn-ing or overheating, show an improper combination of aggregates, show a separation of the bituminous material from the aggregates, or fail to conform to specification requirements, it will be rejected. Provide an adequate access point at the mixer discharge for sampling. If the unsatisfactory mix, as referred to above, is still in the truck, dispose of the mix, or if it has been placed, remove, dispose, and replace the mix.

Immediate control of the asphalt content for bituminous mixtures will be accomplished by testing the com-pleted mixture according to Test Method No. Nev. T761.

For the job mix formula values listed in Subsection 401.02.02, take corrective measures at the plant before production continues if two consecutive test results indicate the material is out of tolerance. If three consecu-tive test results for any one job mix formula property are outside of tolerance, cease production until test results or other information satisfactorily indicate that the next material to be produced will meet the specified values.

When directed, produce a sufficient quantity of bituminous mixture to prove the material is within specifica-tion prior to beginning full production.

Delay bituminous mixture production 24 hours from completion of calibration of the plant according to Subsection 401.03.01, in order for the Engineer to calibrate the Asphalt Content Tester.

401.03.10 Spreading and Finishing. Place each course of the plantmix bituminous surface full width.

Any portion of the course may be advanced only to the extent of one day’s operation before beginning work on a succeeding width. Complete the course to its full plan width before any general longitudinal advancement beyond the width first placed. Bring all portions of the course to as near the same point as practicable before suspending paving operations for more than one day, unless otherwise ordered.

Dump and spread the hot mix asphalt on the prepared surface with the spreading and finishing machine.

If windrow pick-up equipment is used, make it capable of removing and loading all of the mixture deposited on the roadbed into the spreading and finishing machine.

Do not turn hauling equipment in areas where such turning may…