SECTION 7021 - HOT MIX ASPHALT OVERLAYS
HMA Overlays
Includes the requirements for the construction of HMA overlay surface course placed upon an existing pavement.
Comply with Division 1 - General Provisions and Covenants and Section 7020, 1.03.
Comply with Division 1 - General Provisions and Covenants.
1.05 DELIVERY, STORAGE, HANDLING, AND SALVAGING
Comply with Division 1 - General Provisions and Covenants and Section 7020, 1.05.
Comply with Division 1 - General Provisions and Covenants, as well as Section 7020, 1.06.
None.
Comply with Section 7020, 1.08, except as modified herein:
1. Measurement: Measurement will be in tons of HMA overlay.
2. Payment: Payment will be at the unit price per ton of HMA overlay.
3. Includes: Unit price includes, but is not limited to, asphalt mix with asphalt binder, tack coats between layers, construction zone protection, and quality control.
B. HMA Overlay by Square Yards:
1. Measurement: Measurement will be in square yards for each different thickness of HMA overlay. The area of manholes, intakes, or other fixtures in the pavement will not be deducted from the measured pavement area.
2. Payment: Payment will be at the unit price per square yard for each thickness of HMA overlay.
3. Includes: Unit price includes, but is not limited to, asphalt mix with asphalt binder, tack coat, construction zone protection, and quality control.
Comply with Iowa DOT Section 2303, with the following exception:
Follow the procedure outlined in Iowa DOT Materials I.M. 510 for HMA mixture designs, except replace Table 1 in Appendix A, HMA Mixture Design Criteria with the SUDAS HMA Mixture Design Criteria (Table 7020.01) (Tables 2 through 4 in Appendix A still apply).
2.02 WARM MIX ASPHALT MATERIALS
If use of warm mix asphalt (WMA) is approved by the Jurisdiction, comply with Iowa DOT Section 2303.
2.03 RECYCLED ASPHALT MATERIALS
When recycled asphalt materials (RAM) are used and they exceed 20% replacement of the total binder, the binder grades may need to be modified. Comply with Iowa DOT Materials I.M. 510.
A. Recycled Asphalt Pavement: If use of recycled asphalt pavement (RAP) is approved by the Jurisdiction, comply with Iowa DOT Section 2303.
B. Recycled Asphalt Shingles: If use of recycled asphalt shingles (RAS) is approved by the jurisdiction, comply with Iowa DOT Section 2303.
A. Conventional Overlays: Use the specified binder grade meeting the following requirements.
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Asphalt Mixture |
PG Binder |
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Design Traffic (1 x 106 ESALs) |
Mix Designation |
Design Traffic (1 x 106 ESALs) |
Design Speed (MPH) |
|
|
|
≤ 0.3 M |
LT |
≤ 0.3 M |
and |
≤ 45 |
58-28S |
58-28S |
0.3 M to 1 M |
ST |
0.3 M to 1 M |
and |
> 45 |
58-28S |
58-28S or |
0.3 M to 1 M |
ST |
0.3 M to 1 M |
and |
15 to 45 |
58-28S2 |
58-28S2 or 58-34S1,3 |
1 to 10 M |
HT |
1 to 10 M |
and |
15 to 45 |
58-28H |
58-34H |
Overlays |
LT/ST/HT |
≤ 10M |
and |
15 to 45 |
64-22S4 or 58-28S or H |
58-28S or H |
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L = Low S = Standard H = High |
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1 Use of PG 58-34 binder should consider the low temperature reliability in the project area, the availability and cost of different binders, and the ability of the contracting agency to provide on-going maintenance activities. 2 Use of PG 58-28H should be considered if heavy truck or bus traffic is present 3 For high traffic roadways use 58-34H binders 4 If methods are used to retard reflective cracking, PG 58-28S or H is recommended |
B. HMA Interlayer: Use PG 58-34E meeting AASHTO T 321 with minimum 100,000 cycles to failure. Comply with Iowa DOT Materials I.M. 510A. Do not use RAP.
C. High Performance Thin Lift: Use PG 58-34E meeting AASHTO T-324 with minimum 90% elastic recovery. Comply with Iowa DOT I.M. 510A. Do not use RAS.
2.05 HIGH PERFORMANCE THIN LIFT
Design Gyrations |
50 |
Design Target (%Gmm) |
3.0 |
Film Thickness |
8.0 to 13.0 |
Aggregate Quality |
A |
Minimum crushed content |
50% |
FAA minimum |
40 |
Minimum sand equivalency |
50 |
VMA |
16% |
Friction Aggregate |
Minimum 50% Type 4 or better |
B. Replacement: Do not use more than 15% binder replacement. Do not use RAS.
C. Hamburg Testing: Compact to 3.5% air voids. No more than 8 mm rutting in first 8,000 passes.
Sieve Size |
Minimum Percent Passing |
Maximum Percent Passing |
1 1/2” |
|
|
1” |
|
|
3/8” |
91 |
100 |
No. 4 |
|
90 |
No. 8 |
27 |
63 |
No. 16 |
|
|
No. 30 |
|
|
No. 50 |
|
|
No. 100 |
|
|
No. 200 |
2 |
10 |
2.06 NOMINAL AGGREGATE SIZE FOR ASPHALT OVERLAYS
Nominal aggregate size dictates lift thickness. Minimum lift thickness should be at least 3 times the nominal maximum aggregate size to ensure aggregate can be aligned during compaction to achieve required density. Therefore, desired lift thickness can direct the decision on nominal aggregate size to use.
PART 3 - EXECUTION
Comply with Section 7020, Iowa DOT Section 2303, Section 7040, and the following:
A. Preparation of Existing Pavement:
1. Remove pavement by
milling as required by the contract documents. Mill to the depth, cross
section, or profile specified.
2. Sweep existing pavement with approved broom. Provide dust control during brooming.
3. If milling is not required, correct irregularities in existing pavement cross slope with partial patching, full-depth patching, and leveling base coat prior to placing the overlay. Use base or intermediate course mixes to correct irregularities. Surface course thickness per plan.
B. Special Requirements for Thin Lift Overlays and HMA Interlayer:
1. Apply tack coat prior to placement of thin lift overlay and HMA interlayer. Comply with Section 7020.
2. Compact with steel wheel roller.
3. Do not pave unless ambient air temperatures are at least 60°F and rising.
Comply with Section 7020, 3.03.
Comply with Section 7020, 3.04.
Comply with Section 7020, 3.05.
A. General: Comply with Section 7020, 3.06.
B. Special Requirements for Thin Lift Overlays and HMA Interlayer:
1. Complete field voids for Class II compaction as defined in Iowa DOT Section 2303.
2. Sample and test at least one hot box per day of production unless otherwise approved by the Engineer. Apply Iowa DOT Article 2303.05, A, 3 for AAD acceptance. Air void target is based on approved JMF.
3. Take at least one cold feed each day for gradation control.
Comply with Section 7040.
END OF SECTION