Item 442  Superpave Asphalt Concrete

442.01  Description

442.02  Type A Mix Design

442.03  Type B Mix Design

442.04  Asphalt Binder

442.05  Quality Control

442.06  Compaction

442.07  Acceptance

442.08  Basis of Payment

 

442.01  Description.  This work consists of gyratory mix design, material, and quality control requirements for constructing a Superpave asphalt concrete pavement surface or intermediate course.  The asphalt concrete pavement course consists of aggregate, and asphalt binder mixed in a central plant and spread and compacted on a prepared surface.

The requirements of Item 441 apply, except as modified by this specification.

442.02  Type A Mix Design.  Design the mixture composition for a Type A mix according to 441.02 and the most recent Asphalt Institute Superpave Mix Design Manual (SP-2) for design procedures and material properties except as modified by this subsection.  Include in the JMF submittal the standard Department cover and summary page; all printouts from the gyratory compactor (all gyratory points not necessary); and analysis covering the required mix properties.  Submit one compacted gyratory sample and loose mix for compaction of another sample, in addition to a 5-pound (2000 g) loose sample, for each JMF.

The Contractor may use the Marshall flow test in design as an indicator of potential for excess tenderness.

Set the design gyrations according to the lane current average daily truck traffic (Lane ADTT) as follows unless otherwise shown on the plans:

 

Where:

     Current ADT =  current average daily traffic count from the plans

                  T24 =  percent trucks per day from the plans

 

Table 442.02-1  Gyration Level and Material Requirements

Lane

ADTT

Nini

Ndes

Nmax

Coarse

Aggregate

Angularity

Fine

Aggregate

Angularity

Flat and

Elongated

Particles

Sand

Equivalent

<4000

7

65

105

95/90

44

10

45

>4000

7

65

105

100/100

44

10

50

 

If multiple Ndes exist due to a multiple section project, etc., apply the lower design gyrations unless otherwise shown on the plans.

Submit aggregate to be used to the Laboratory for approval a minimum of 3 weeks before submitting a JMF for approval.

If fine aggregate is from crushed carbonate stone or air-cooled blast furnace slag, the Department will not require the fine aggregate angularity (FAA) test.  The Department will allow a blend of a material not meeting the FAA with a material that meets the FAA, but calculate the FAA result based on the individual Department FAA results and actual blend percentages.  The Department must approve blends.

The restricted zone does not apply.  Use control points according to SP-2, except as specified in Table 442.02-2.

Table 442.02-2  Aggregate Gradation Requirements

Sieve Size

9.5 mm mix

(% passing)

12.5 mm mix

(% passing)

19 mm mix

(% passing)

1 1/2 inch (37.5 mm)

 

 

100

3/4 inch (19 mm)

 

100

85 to 100

1/2 inch (12.5 mm)

100

95 to 100

90 max

3/8 inch (9.5 mm)

90 to 100

 

 

No. 4 (4.75 mm)

70 max

 

 

No. 8 (2.36 mm)

32 to 52

32 to 45

28 to 45

No. 200 (75 µm)

2 to 8

2 to 8

2 to 6

 

Ensure that the F/A ratio is a maximum of 1.2.  Use a 2-hour cure in design process.

If more than 15 percent fine aggregate not meeting FAA is used, perform a loaded wheel test (LWT) according to Supplement 1057.  To estimate a LWT sample mix volume, use the bulk density from gyratory specimens at Ndes.  Results less than 0.20 inch (5.0 mm) at 115 °F (46 °C) are considered passing.

The Contractor may use reclaimed asphalt concrete pavement according to 401.04 in surface courses or up to 20 percent in intermediate courses.  Test design volumetric properties at Ndes.  Test Nmax for the required criteria.  Ensure that the VMA is not less than the minimum values of Table 442.02-3.

Table 442.02-3  VMA Criteria

Mix

VMA (percent minimum)

9.5 mm

15

12.5 mm

14

19.0 mm

13

 

442.03  Type B Mix Design.  Apply the mix design specified in 442.02 for a Type A mix except as modified by this subsection:

Modify the Coarse Aggregate Angularity of Table 442.02-1 according to Table 442.03-1.

Table 442.03-1

Lane ADTT

Coarse Aggregate Angularity

<4000

65/65

>4000

75/70

 

Ensure that at least 50 percent by weight of virgin fine aggregate is aggregate meeting FAA or is crushed carbonate stone or air-cooled blast furnace slag.  Modify the No. 8 (2.36 mm) sieve requirement for a 12.5 mm mix in Table 442.02-2 to 34 to 40 percent.  Apply an F-T value of +2 according to 441.02 and 441.09.

442.04  Asphalt Binder.  Use a PG 70-22M asphalt binder for surface courses and a PG 64-28 asphalt binder for intermediate courses.

The minimum total asphalt binder content for a surface course is 5.7 percent.

442.05  Quality Control.  Conform to 441.09, except as specified in this subsection.  Ensure that plant operation and quality control testing conform to the Contractor’s Quality Control Program (QCP).

Use a gyratory compactor conforming to the requirements of Superpave and verified by FHWA.  If the gyratory compactor was moved to the plant before production, calibrate it and present the results to the DET.  Condition samples for air voids for 2 hours.

Determine bulk gravity for air voids determination on specimens compacted to Ndes.  Once each day for the first 3 production days, and once each third production day thereafter compact one set of specimens to Nmax.  Ensure that density at Nmax is less than 98.0 percent of MSG.  The Department will not allow production to continue if Nmax is greater than or equal to 98.0 percent of MSG unless acceptable corrections and retest are made.

If the design gradation requires an LWT test, take a sample sufficient to compact one LWT test beam once each day for the first 3 days and test it according to Supplement 1057.  The Contractor may perform the LWT test in the Contractor’s Level 2 laboratory, but must compact the sample beam the same day the sample was taken, cure it overnight, and test it the following day.  Give the test result and beam density to the DET the day of the LWT test.  Report the LWT data on the Quality Control Report.

At least once a week, the Department monitor will instruct the Contractor to obtain asphalt binder samples.  Take two 1-quart (1 L) asphalt binder samples for each asphalt binder type used.  Take these samples between the last piping “Tee” in the line and the inlet into the asphalt plant.  Label the samples with the asphalt binder type, supplier, project number, and date.  Retain them in the plant laboratory for future reference by the Department.  Hold these samples until otherwise notified by the Department monitor.

442.06  Compaction.  If the rollers are staying far behind the paver on a mix at normal compaction temperature, it is an indication of a tender, rut prone mix, and may be justification for the Department to require a redesign.

442.07  Acceptance.  The Department will base acceptance of the asphalt concrete mix on the item specified in the Contract (i.e., Item 446, Item 448).

442.08  Basis of Payment.  The Department will pay for accepted quantities at the contract prices as follows:

Item           unit                                Description

442             Cubic Yard                      Asphalt Concrete Surface
                   (Cubic Meter)                    Course, 12.5 mm, Type A (446)

442             Cubic Yard                      Asphalt Concrete Surface
                       (Cubic Meter)                 Course, 12.5 mm, Type B (446)

442             Cubic Yard                      Asphalt Concrete Surface
                       (Cubic Meter)                 Course, 9.5 mm, Type A (446)

442             Cubic Yard                      Asphalt Concrete Surface
                       (Cubic Meter)                 Course, 9.5 mm, Type B (446)

442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Intermediate Course, 19 mm, Type A (446)

442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Intermediate Course, 19 mm, Type B (446)
442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Intermediate Course, 9.5 mm, Type A (448)

442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Intermediate Course, 9.5 mm, Type B (448)

442             Cubic Yard                      Asphalt Concrete Surface
                       (Cubic Meter)                 Course, 12.5 mm, Type A (448)

442             Cubic Yard                      Asphalt Concrete Surface
                       (Cubic Meter)                 Course, 12.5 mm, Type B (448)

442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Surface Course, 9.5 mm, Type A (448)

442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Surface Course, 9.5 mm, Type B (448)

442             Cubic Yard                      Asphalt Concrete
                       (Cubic Meter)                 Intermediate Course, 19 mm, Type A (448)

442             Cubic Yard                      Asphalt Concrete 
                       (Cubic Meter)                 Intermediate Course, 19 mm, Type B (448)