Minimum Requirements for Furnishing and Installing Asphalt Concrete

1.         PURPOSE

 

1.1       This specification defines for the contractor the minimum requirements for furnishing and installing asphalt concrete.

 

 

2.         Scope

 

2.1       The contractor shall provide all labor, supervision, tools, equipment, engineering, surveying, and materials to perform the asphalt paving work in strict accordance with this specification and all other contract documents.

 

 

3.         RELATED DOCUMENTS

 

3.1       American Association of State Highway and Transportation Officials (AASHTO)

 

T11         Materials Finer Than 0.075 mm (200) Sieve in Mineral Aggregates by Washing

T19         Bulk Density and Voids in Aggregate

T30         Mechanical Analysis of Extracted Aggregate

T96         Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine

T245       Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus

 

3.2       American Society for Testing and Materials (ASTM)

 

D 1557    Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3))

D 2172    Test Methods for Quantitative Extraction of Bitumen from Bituminous Paving Mixtures

D 3381    Specification for Viscosity-Graded Asphalt Cement for Use in Pavement Construction

D 4318    Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils

 

3.3       The Asphalt Institute (AI)

 

MS-2       Mix Design Methods for Asphalt Concrete and Other Hot-Mix Types

 

 

4.         ASPHALT DESIGN MIX

 

4.1       One week after contract award the contractor shall submit, for Air Products approval, a design mix that has been developed according to the provisions of this specification. The mix shall include test data certifying that mixtures conforming to the proposed design mix will have the properties as specified.

 

4.2       Bituminous Material

 

4.2.1   The bituminous material that is used in the design mix shall meet the requirements of viscosity grade AC-20, ASTM D 3381. The contractor shall submit a certification from the bituminous supplier that the material meets the above specification. This shall be done for every batch delivered to the plant and used in the production of the design mix. The contractor shall supply a sample to the Air Products designated laboratory for a penetration test to ensure continuous quality.

 

4.2.2   The design mix shall propose definite values for the percentage (in units of one-tenth of one percent) of bituminous material to be added, based on the total weight of the mixture. The following general composition limits are extreme ranges within which the design mix must be established:

 

Minimum          4.0%

Maximum         10.0%

 

4.3       Aggregate Material

 

4.3.1   The aggregate material that is used in the design mix shall consist of crushed stone, crushed gravel, or crushed slag and shall have a percentage of wear not exceeding 50 as determined by AASHTO T96.

 

4.3.2   The aggregate shall be of uniform density and quality with a rodded unit weight of not less than
75 pounds per cubic foot (PCF) determined by AASHTO T19.

 

4.3.3   The design mix shall propose definite values for the percentage of aggregate passing each specified sieve, based on the dry weight of aggregate. The following general composition limits are extreme ranges within which the design mix must be established:

 

 

 

Sieve Size

Total Percent Passing

(percent by weight)

   
1 inch 100
3/4 inch 76–100
1/2 inch 66–86
3/8 inch 57–77
No. 4 40–60
No. 8 26–46
No. 6 17–37
No. 30 11–27
No. 50 7–19
No. 100 6–16
No. 200 3–6

 

 

4.3.4   Coarse aggregate, retained on the No. 8 sieve, shall consist of clean, hard, tough, durable, and sound fragments and shall be free from organic matter or other deleterious substances.

 

4.3.5   That portion of the aggregate retained on the No. 8 sieve shall have not less than 50% of particles by weight with at least two or more mechanically fractured faces and 85% having at least one fractured face.

 

4.3.6   Fine aggregate passing the No. 8 sieve may be either a natural or manufactured product. The aggregate shall be clean, hard grained, and moderately sharp and shall contain not more than 2% by weight of vegetable matter or other deleterious substance.

 

 

4.3.7   That portion of the material passing the No. 200 sieve shall have a plasticity index not greater than 4 when tested according to ASTM D 4318.

 

4.3.8   The weight of minus 200 mesh material retained in the aggregate, as determined by the difference in percent passing a No. 200 sieve by washing and dry sieving without washing, shall not exceed 6% of the total sample weight.

 

4.3.8.1            The portion of fine aggregate passing the No. 200 sieve shall be determined by washing with water according to AASHTO T11.

 

4.3.9   The contractor shall submit samples to the Air Products designated laboratory for gradation, specific gravity, absorption, and sodium sulfate soundness tests.

 

4.4       The design mix shall include the mixing temperature. Extreme ranges within which the design mix must be established are:

 

Minimum    135C   (275F)

Maximum   162C   (325F)

 

4.5       The design mix shall have properties as listed below as determined by a Marshall analysis:

 

 

  Property Test Method Acceptable Range of Values
       
  Number of Blows AASHTO T245 50
       
  Stability, Pounds AASHTO T245 1200 minimum
       
  Flow, 0.01 Inches AASHTO T245 8–16
       
  Percent Air Voids AI MS-2 3–5
       
  Voids in Mineral Aggregate (VMA) AI MS-2 13 minimum

 

4.5.1   The contractor shall submit a minimum of six test results, taken in the last two years, which indicate that the proposed design mix conforms to the above properties.

 

 

5.         MIXING REQUIREMENTS

 

5.1       It is the intent of this specification to require the contractor to produce a mixture of uniform composition conforming closely to the approved design mix and meeting the requirements of Section 4.

 

5.2       During mixing, Air Products will require daily extraction tests for bitumen content and aggregate gradation through its designated material testing laboratory. The mixture will be tested for bitumen content according to ASTM D 2172 and for aggregate gradation according to AASHTO T30. Tests on Marshall specimens shall be made daily according to AASHTO T245. The mixture shall comply with the requirements of paragraph 4.5 when tested according to the Marshall method procedures contained in Chapter III of the AI Manual, Series No. 2 (MS-2).

 

5.3       The Air Products designated material testing laboratory shall record mix temperatures daily and review for compliance with paragraph 4.4.

 

 

5.4       Design mix tolerances are shown below and shall be applied to the design mix formula to establish a job control grading band. Tolerances that result in a job control grading band outside the master grading band as stated in paragraphs 4.2.2, 4.3.3, and 4.4 are not allowable.

 

  Material Tolerance Plus or Minus
     
  Aggregate Passing No. 4 Sieve or Larger 7%
     
  Aggregate Passing No. 8 Sieve 6%
     
  Aggregate Passing No. 30 and 50 Sieves 5%
     
  Aggregate Passing No. 100 and 200 Sieves 3%
     
  Bitumen 0.5%
     
  Temperature of Mix 20F

 

5.5       Results from the extraction test will be compared with the design mix specification. If there is a deviation from the design mix, the Air Products designated material testing laboratory will immediately notify mixing plant personnel and Air Products and halt delivery of the mix to the construction site. Immediate corrective action shall be taken by the mixing plant. The Air Products representative will determine the acceptability of any incorrect mix that has been placed before discovery. This may include removal and replacement, which would be to the contractor’s account.

 

5.6       The contractor shall fully cooperate with the Air Products designated material test laboratory and shall provide whatever samples and assistance required.

 

5.7       The mineral aggregate shall be dried before mixing. Drying shall be accomplished in a suitable drier and shall continue until the average moisture content is not more than 1% by weight. Moisture determinations shall be made on samples taken from the drier discharge. Flames used for drying and heating shall be properly adjusted to avoid damage to the aggregate and to avoid contamination of the aggregate by soot or fuel oil.

 

5.8       The shortest mixing time consistent with satisfactory coating of the aggregate shall be used. The mineral aggregate shall be considered satisfactorily coated with bitumen when all of the particles passing the No. 4 sieve and 96% of the particles retained on the No. 4 sieve are coated.

 

5.9       If a drier-drum mixing process is used, the drier-drum mixing system shall be equipped to provide positive control of the cold aggregate feed and automatically regulate the feed gate and permit instant correction of variations in the load. The cold feed shall be automatically coupled with the bitumen flow to maintain the required proportions. The system shall be equipped with automatic burner controls and shall provide for temperature sensing of the bituminous mixture at discharge.

 

5.9.1   The mixing system shall be equipped with an adequate and approved surge bin capable of dumping into hauling units. The surge bin shall be loaded in a manner to prevent segregation of the mix. Dumping on the ground and reloading of the bituminous mix shall not be permitted.

 

 

6.         ASPHALT CONCRETE PLACEMENT

 

6.1       Subgrade Preparation

 

6.1.1   The asphalt paving shall be placed on top of a shaped and compacted subgrade. The contractor shall survey the existing subgrade with a registered surveyor and submit an “as is” drawing of the area to be paved.

 

6.1.2   The contractor shall shape the existing subgrade to meet the elevation requirements as indicated on the drawings and specifications. Any additional crushed rock that may be required to bring up the grade to that required will be on a “as placed” unit price basis as established by the contract. All placed rock must be compacted to not less than 95% of the maximum dry density as determined by modified Proctor ASTM D 1557.

 

6.1.3   The roadway base course shall be reshaped as necessary to maintain general slopes from high points to catch basins or to reestablish areas such as roadway cross slopes and warped areas.

 

6.1.4   Elevations shown on the drawings shall be the finish grade at the top of the paving to which the contractor shall work. Finish grade elevations may be varied only when the top of the new paving must be set flush with existing concrete surfaces (i.e., the truck scale, trailer loading slab, fuel island, liquid oxygen (LOX) pump/meter test pad, trailer wheel stop, and landing gear pad).

 

6.1.5   After reshaping and rehabilitation, the subgrade shall be given a proof roll test by the contractor. All areas to be paved shall be rolled with a loaded 10-ton dump truck. This proof roll must be witnessed and accepted by the Air Products representative and the Air Products designated soil testing laboratory. Those areas that are unacceptable and were placed by previous contractors will be repaired on a unit price basis as established by the contract. Unacceptable areas placed by the contractor must be repaired to the contractor’s account.

 

6.1.6   All subgrade to be paved shall be primed before placement of the asphalt.

 

6.2       Spreading and Compaction

 

6.2.1   The bituminous mixture shall be spread with self-propelled, vibratory, mechanical spreading and finishing equipment capable of spreading at least a 3.6 m (12 ft) width.

 

6.2.2   A motor grader or other method of spreading the material may be used (if approved by the Air Products representative) for small projects under 20 tons, for irregular areas and miscellaneous construction (such as sidewalks), and for the initial leveling course where the base is placed on an existing pavement.

 

6.2.3   The mixture shall be spread and struck off in such a manner that the finished surface shall conform to the elevations, grades, and cross sections shown on the plans or as designated by the Air Products representative.

 

6.2.4   Unless otherwise designated or directed, the bituminous surface course [more than 100 mm (4 in) in total compacted thickness] shall spread in two or more courses with no course exceeding 100 mm (4 in) in compacted thickness.

 

6.2.5   Longitudinal joints, in succeeding courses, shall be offset at least 150 mm (6 in) transversely to avoid a vertical joint through more than one course.

 

6.2.6   After the mixture has been spread, the surface shall be longitudinally rolled beginning at the outside edge or lower side and proceeding toward the higher side. Each pass of one roller shall overlap the preceding pass by at least one-half the width of the roller. Rolling operations shall be conducted in such a manner that shoving or distortion will not develop beneath the roller.

 

6.2.7   When placing more than one lift, all courses shall be properly rolled and compacted. If longitudinal joints exist that have hardened, have been driven upon, or have become contaminated, these edges shall be tacked before placing an adjacent layer.

 

6.2.8   Nuclear density tests shall be taken by the Air Products designated testing laboratory to determine the density of newly placed asphalt paving. The minimum acceptable density with the nuclear density test shall be 96%. Test areas below 96% are unacceptable and must be immediately rerolled and retested until 96% density is obtained. These are intended to provide continual feedback to the contractor as to the density acceptance. Final acceptance of asphalt paving will be determined from the analysis of core samples. The frequency of these tests will be according to Section 6.

 

6.2.9   The bituminous mixture shall not be placed on a wet surface or when the surface temperature of the underlying course is less than specified below. The temperature requirements may be waived, but only at the discretion of the Air Products representative.

 

 

Base Temperature Limitations
Course Thickness Base Temperature (Minimum)

             C                       F

   
75 mm (3 in) or greater              4                         40
   
Greater than 25 mm (1 in)              7                         45
but less than 75 mm (3 in)  
   
25 mm (1 in) or less            10                         50

 

 

6.3       Miscellaneous

 

6.3.1   The 900 mm (3 ft) wide tapered shoulders shall be constructed with yard surfacing aggregate. See the drawings for the gradation table and material description. The density of the compacted material shall not be less than 95% of the maximum dry density as determined by modified Proctor ASTM D 1557.

 

6.3.2   Lines painted on the asphalt pavement to delineate parking stalls shall be 100 mm (4 in) wide. Paint shall be spray applied and shall be chlorinated rubber yellow traffic paint No. 20202 as manufactured by Centerline Supply or approved equal.

 

6.3.3   The contractor shall take whatever steps, procedures, or means required to prevent abnormal dust conditions due to construction operations. The dust control measures shall be maintained at all times. The contractor shall fully describe in the bid what procedures the contractor will follow to accomplish effective dust control.

 

 

7.         TESTING AND INSPECTION

 

7.1       All material and workmanship shall be subject to inspection and examination by the Air Products representative or Air Products designated material testing laboratory. Any defective material or workmanship shall be corrected to the Air Products representative’s satisfaction by the contractor to the account of the contractor.

 

 

7.2       Air Products shall, through their designated material testing laboratory, perform those tests as indicated in previous sections of this specification. If the contractor does not accept the findings of the Air Products designated testing laboratory, the contractor has the option of obtaining an additional third party testing laboratory report at contractor’s expense. The contractor will submit to the Air Products representative two test results for every one taken by the Air Products designated testing laboratory. These test results must fully support the criteria of acceptability of this specification to be considered by the Air Products representative, who shall have final acceptability determination.

 

7.3       Final acceptance of the in-place asphalt paving shall be determined by cores as taken and analyzed by the Air Products designated material testing laboratory. The core holes shall be repaired by the contractor. The acceptability of these cores shall be according to this specification, the approved asphalt design mix, and a minimum 96% density.

 

7.4       The following tests shall be performed at the job site by the Air Products designated material testing laboratory:

 

Nuclear density test on subgrade.

 

Nuclear density test on each course of asphalt paving.

 

Record temperatures of asphalt being spread.

 

Core samples that will be analyzed for depth, density, and conformance to the approved asphalt design mix.

 

7.5       The criteria for the frequency of testing as indicated in Section 6 is as follows:

 

Roadways

 

–     Roadways/driveways submitted to normal wear by automobiles and occasional tractor/trailer use shall be tested to a linear dimension of every 30.5 m (100 ft).

 

–     Roadways/driveways submitted to frequent tractor/trailer use shall be tested to a linear dimension of every 15.2 m (50 ft).

 

Parking Areas

 

–     Parking areas normally used for automobiles and subject to normal wear shall be tested every 232.2 sq m (15.2 x 15.2 m grid). The Imperial Unit equivalent is 2500 sq ft (50 x 50 ft grid).

 

–     Parking areas for tractor/trailers shall be tested every 58 sq m (7.6 x 7.6 m grid). The Imperial Unit equivalent is 625 sq ft (25 x 25 ft grid).

 

–     Each test shall be taken in a different location within each grid.

 


 

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