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SECTION 32 12 16
SECTION 32 12 16
HOT-MIX ASPHALT (HMA) FOR ROADS
PART 1 GENERAL
| 1.1 | SECTION INCLUDES |
| A. | Products and procedures for placing and compacting one or more layers of HMA comprised of aggregate, asphalt binder, hydrated lime and other additives. |
| B. | Option to incorporate Reclaimed Asphalt Pavement (RAP) materials into HMA pavement. |
| 1.2 | REFERENCES |
| A. | AASHTO M 323: Superpave Volumetric Mix Design |
| B. | AASHTO R 35: Standard Practice for Superpave Volumetric Design for Hot-Mix Asphalt (HMA) |
| C. | AASHTO T 19: Unit Weights and Voids in Aggregate |
| D. | AASHTO T 89: Determining the Liquid Limit of Soils |
| E. | AASHTO T 90: Determining the Plastic Limit and Plasticity Index of Soils |
| F. | AASHTO T 96: Resistance to Abrasion of Small Size Coarse Aggregate by Use of the Los Angeles Machine |
| G. | AASHTO T 104: Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate |
| H. | AASHTO T 112: Clay Lumps and Friable Particles in Aggregate |
| I. | AASHTO T 176: Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test |
| J. | AASHTO T 195: Determining Degree of Particle Coating of Bituminous Aggregate Mixtures |
| K. | AASHTO T 255: Total Moisture Content of Aggregate by Drying |
| L. | AASHTO T 304: Uncompacted Void Content of Fine Aggregate |
| M. | AASHTO TP 61: Determining the Percentage of Fractured Particles in Coarse Aggregate |
| N. | UDOT Materials Manual of Instruction |
| O. | UDOT Minimum Sampling and Testing Requirements |
| 1.4 | SUBMITTALS |
| A. | Submit mix design at least 14 calendar days before paving. |
| B. | Submit verification that hydrated lime meets the requirements. |
| C. | Submit verification that asphalt binder meets the requirements of Section 32 12 03. |
| D. | Changes in job mix targets: |
| 1. | Submit a written request for a change in the job-mix gradation at least 48 hours before incorporating changes into production. |
| a. | Include documentation, Contractor QC test data, supporting correlation between suggested target changes and mix design volumetric requirements. |
| b. | Contractor shall perform field volumetric mix design verification at no additional cost to the Government. Field volumetric mix design verification consists of three sets of two gyratory specimens run at the new target gradation or asphalt binder content or both. Previous acceptance tests for the same field volumetric mix design from within the past two years are acceptable for field verification. |
| c. | Submit a new laboratory volumetric mix design from a laboratory qualified by UDOT if the field volumetric mix verification does not meet the volumetric requirements. Allow at least four working days for Contractor field verification and COR acceptance. |
| E. | Submit a new laboratory volumetric mix design if changes occur in the aggregate source, asphalt binder source, or grade. |
| 1.6 | ACCEPTANCE |
| A. | Acceptance sampling and testing of material is as specified herein. |
| B. | Gradation and asphalt binder content |
| 1. | A lot equals the number of tons of HMA placed during each production day. The COR evaluates a lot on the test results of four samples with the following exceptions: |
| a. | Compute disincentive using the test results from three samples if only three samples can be taken for the production day. |
| b. | Add the lot to the next day’s production if three random samples cannot be taken. |
| c. | Add the lot to the previous day’s production for the final day’s production if three random samples cannot be taken. |
| d. | The lot may be increased to include up to three production days when agreed upon in advance by both the Contractor and the COR when less than 900 tons are anticipated per production day. |
| 2. | Aggregate: Verify gradation prior to the drum mixer or after going through the drier. |
| 3. | Asphalt shall meet the requirements specified herein and in Section 32 12 03. |
Table 1: Asphalt Binder Content Pay Factors
| Pay Factor |
| Mean Absolute Deviation from Job Mix Formula |
Table 2: Aggregate Gradation Pay Factors
| Sieve Size |
| Pay Factor |
| Mean Absolute Deviation |
| 1/2 inch and larger |
| 1.00 |
| 0.0 to 5.6 |
| D. | Density and Thickness |
| 1. | The COR evaluates a lot on the test results of two samples per lot. Lot size is 1,000 square yards or part thereof. |
| 2. | Contractor obtains cores within two days after the pavement is placed. |
| a. | COR marks coring location for in-place density and joint density cores. |
| b. | Move transversely to a point 1 ft from the edge of the pavement for In-place density if the random location for coring falls within 1 ft of the edge of the overall pavement section (outer part of shoulders). |
| c. | Fill core holes with HMA or high AC content cold mix and compact as approved by the COR. |
| d. | The Government witnesses the coring operation and testing the cores begins within 24 hours for density acceptance. |
| 3. | Density Requirements |
| a. | The target for in-place density including longitudinal joint density is 93.5 percent of Maximum Specific Gravity for projects where the design thickness is greater than 2 inches. |
| b. | The target for in-place density including longitudinal joint density is 92.5 percent of Maximum Specific Gravity for projects where design thickness is less than or equal to 2 inches. |
| c. | Use the average of the Maximum Specific Gravity tests for each lot. |
| d. | Acceptance for in-place density may be based on establishing a rolling pattern for bridge decks, utility work, traffic signals, detours, lane leveling, driveways, etc, or small projects with plan quantities less than 3,000 tons. |
| 4. | Thickness Requirements |
| a. | The Government accepts a lot for thickness when: |
| 1) | The average thickness of all sublots is not more than 1/2 inch greater nor 1/4 inch less than the total thickness specified. |
| 2) | No individual sublot shows a deficient thickness of more than 3/8 inch. |
| b. | Excess Thickness: The COR may allow excess thickness to remain in place or may order its removal. |
| 1) | The Government pays for 50 percent of the mix for material in excess of the +1/2 inch tolerance when excess thickness is allowed to remain in place. |
| c. | Deficient Thickness: Place additional material where lots or sublots are deficient in thickness. |
| 1) | The Government pays for material necessary to reach specified thickness. |
| 2) | The Government pays for 50 percent of the mix for additional material over specified thickness necessary to achieve minimum lift thickness. |
| 3) | Minimum compacted lift is 3 times the nominal maximum aggregate size. |
| 4) | At COR’s discretion, a lot with a deficient thickness greater than 1/4 inch may stay in place at the reduced pay factor as listed in Table 4. |
| d. | Thickness tolerances established above do not apply to leveling courses. Check final surfaces in staged construction. |
| e. | Thickness acceptance for thin lift projects of 2 inches or less consists of checking thickness regularly with a depth probe during placement and taking corrective action as necessary. |
| 5. | Compaction determinations are full core depth or overlay depth in overlay construction. |
| 6. | Based upon core samples, compaction and thickness is acceptable if test deviations are within pay factor 1.00 limits. At COR’s discretion, a lot with a test deviation greater than Reject may stay in place at 50 percent cost. |
Table 3: Density Pay Factors
| Pay Factor |
| Density, in Percent (ASTM D 2041) |
| Average Thickness |
| Lowest Test |
| 0.70 |
| More than 96 |
| More than 96 |
| - |
| 1.00 |
| 93 to 96 |
| 92 to 96 |
| 89 or greater |
| 0.90 |
| 93 to 96 |
| 92 to 96 |
| Less than 89 |
| 0.80 |
| Less than 92 |
| Less than 92 |
| 89 or greater |
| Reject |
| Less than 92 |
| Less than 92 |
| Less than 89 |
Table 4: Thickness Pay Factors
| Pay Factor |
| Thickness Variation, in Inches (ASTM D 3549) |
| 0.50 for excess material |
| Greater than + 0.50 |
| Reject |
| Greater than – 0.75 |
| F. | The COR may elect to accept material on visual inspection for work such as utility work, traffic signals, detours, lane leveling, driveways, etc., or small projects with plan quantities less than 3,000 tons. |
| 1. | The COR reserves the option of requiring the Contractor to conduct any acceptance tests necessary to determine that the material and workmanship meets the project requirements. |
| 2. | Acceptance for density may be based on establishing and maintaining a roller pattern to obtain maximum density without over-stressing the pavement. |
| G. | Smoothness |
| 1. | Lot size is 100 linear feet per lane or part thereof. A minimum of two tests per lot shall be taken in both the longitudinal and transverse directions. |
| 2. | Longitudinal requirement: 1/8 inch in 10 feet parallel to centerline. |
| 3. | Transverse requirement: 1/4 inch in 10 feet perpendicular to centerline except at cross section grade breaks. |
Table 5: Smoothness Pay Factors
| Pay Factor |
| Measurement Deviations, in Percent |
| 4. | Regardless of the above, any small individual area with surface deviation which exceeds the tolerance given above by more than 50 percent, shall be corrected by diamond grinding to meet the specification requirements above or shall be removed and replaced at no additional cost to the Government. |
| H. | For payment of any lot the lowest applicable pay factor for aggregate gradation, asphalt binder content, smoothness, density, and thickness shall be applied to the contract line item cost. |
| I. | Tests listed above are the minimum required to conform to the Contract. If there is reason to suspect non-compliance with the requirements herein or with the requirements specified within the Delivery Order, COR may require Contractor to perform additional tests at no additional cost to the Government. |
PART 2 PRODUCTS
| 2.1 | ASPHALT BINDER |
| A. | Asphalt Material. Refer to Section 32 12 03. |
| 2.2 | AGGREGATE |
| A. | Crusher processed virgin aggregate material consisting of crushed stone, gravel, or slag. |
| B. | Refer to Table 6 to determine the suitability of the aggregate. |
| 1. | Coarse aggregates: |
| a. | Retained on No. 4 sieve. |
| 2. | Fine aggregates: |
| a. | Clean, hard grained, and angular. |
| b. | Passing the No. 4 sieve. |
Table 6: Aggregate Properties – HMA
| Test Method |
| Test No. |
| Test Requirement |
| One Fractured Face |
| AASHTO TP 61 |
| 95% min. |
| Two Fractured Face |
| AASHTO TP 61 |
| 90% min. |
| Fine Aggregate Angularity |
| AASHTO T 304 |
| 45 min. |
| Flakiness Index |
| UDOT MOI 933 (Based on ⅜ inch sieve and above) |
| 17% max. |
| L.A. Wear |
| AASHTO T 96 |
| 35% max. |
| Sand Equivalent |
| AASHTO T 176 (Pre-wet method) |
| 60 min. |
| Plasticity Index |
| AASHTO T 89 and T 90 |
| 0 |
| Unit Weight |
| AASHTO T 19 |
| min. 75 lb/cu ft |
| Soundness (sodium sulfate) |
| AASHTO T 104 |
| 16% max. loss with five cycles |
| Clay Lumps and Friable Particles |
| AASHTO T 112 |
| 2% max |
C. Meet gradation requirements in Table 7 as specified in the Delivery Order documents.
Table 7: Aggregate Gradations (Percent Passing by Dry Weight of Aggregate)
| Control Sieve Size |
| Nominal Maximum Size of Aggregate |
| 1 inch |
| ¾ inch |
| ½ inch |
| ⅜ inch |
| 1 inch |
| 90.0 - 100.0 |
| 100.0 |
| ¾ inch |
| <90 |
| 90.0 - 100.0 |
| 100.0 |
½ inch
⅜ inch
No. 4
< 90
| No. 8 |
| 19.0 - 45.0 |
| 23.0 - 49.0 |
| 28.0 - 58.0 |
| 32.0 - 67.0 |
| No. 200 |
| 1.0 - 7.0 |
| 2.0 - 8.0 |
| 2.0 – 10.0 |
| 2.0 – 10.0 |
| 2.3 | HYDRATED LIME |
| A. | Hydrated Lime shall be added to the mix. |
| 1. | Meet AASHTO M 303, Type I, as specified, and |
| 2. | Conform to the physical requirements of ASTM C 1097, subparagraph d.1, and |
| 3. | Use test method ASTM C 110, paragraph 5.4. |
| B. | Base the amount of hydrated lime used on the dry weight of the aggregate. Use either Method A or B, unless Method B is specified. |
| C. | The hydrated lime shall be considered as mineral filler and shall be considered in the gradation requirements. |
| D. | The amount of hydrated lime or antistripping agent added to the bitumen shall be determined during development of the JMF and shall be sufficient to produce a retained coating area greater than 95 percent. |
| 1. | Use of additional antistripping agent may be directed during progress of the work, if necessary. |
| 2. | No additional payment will be made to the Contractor for addition of antistripping agent required. |
| E. | Method A: Lime Slurry |
| 1. | Create slurry by mixing one part lime and three parts water by weight. |
| 2. | Add lime at a minimum of 1 percent by weight. |
| 3. | Maintain the lime slurry mix in a malted milk consistency. |
| 4. | Deliver lime slurry to the twin shaft pugmill for mixing with aggregate. |
| 5. | Adjust quantity (percent) of lime as necessary, based on results of Hamburg Wheel Tracker test. |
| F. | Method B: Lime and Aggregate Stockpile Marination |
| 1. | Provide sufficient free moisture to thoroughly wet the aggregate and activate the lime before introducing hydrated lime. |
| 2. | Add lime at a minimum of 1.5 percent by weight. |
| 3. | Thoroughly mix wet aggregate/lime mixture in a twin shaft pugmill. |
| 4. | Marinate the aggregate/lime mixture in the stockpile for a minimum of 48 hours. |
| 5. | Adjust quantity (percent) of lime as necessary, based on results of Hamburg Wheel Tracker test. |
| 6. | Use the wet cured aggregate within 60 days. |
| G. | Mixing |
| 1. | For both Methods A and B adjust mixing paddles in the pugmill so that the aggregate being discharged is completely coated by the lime slurry. |
| 2. | Do not allow the volume of material in the pugmill to extend above the vertical position of the blade tips. |
| 2.4 | RECLAIMED ASPHALT PAVEMENT (OPTIONAL) |
| A. | No asphalt binder grade adjustment is necessary when reclaimed asphalt pavement (RAP) is limited to 15 percent by total weight of the hot mix. |
| B. | Adjust asphalt binder grade according to AASHTO M 323 when RAP content is between 15 to 25 percent of the total weight of the hot mix. |
| 1. | Select one grade softer than the grade specified. Do not select any grades lower than PG 64-34. |
| C. | Adjust asphalt binder grade according to AASHTO M 323 Appendix A when RAP content exceeds 25 percent. |
| 1. | Obtain COR’s approval to exceed 25 percent. |
| 2. | Use RAP from a single source. |
| 3. | Provide test reports indicating that the PG grade of the recovered asphalt binder is consistent throughout the stockpile. |
| 4. | Limit RAP to 30 percent of the total weight of the hot mix. |
| D. | RAP aggregate is required to meet Table 5 with exception of Sand Equivalent AASHTO T 176. |
| 2.5 | VOLUMETRIC DESIGN |
| A. | Perform Superpave Volumetric Mix Design according to UDOT Materials Manual of Instruction 960 and the following: |
| 1. | Incorporate hydrated lime into all designs. |
| 2. | Comply with Table 8 and Table 9. |
| B. | The Department Region Materials Lab verifies the Volumetric Mix Design. UDOT Materials Manual of Instruction 960 |
| 1. | Do not begin paving until verification is complete. |
Table 8: Volumetric Design Gyrations
| 20 Years Design ESALS (Million) |
| Compaction Parameters |
| Voids Filled with Asphalt (VFA) (%) |
| Ninitial /% of Gmm* |
| Ndesign /% of Gmm* |
| Nmax /% of Gmm* |
| 0.3 |
| 6/ 91.5 |
| 50/ 96.5 |
| 75/ 98 |
| 70 - 80 ** |
| 0.3 to <3 |
| 7/ 90.5 |
| 75/ 96.5 |
| 115/ 98 |
| 70 - 80 |
| 3 to < 30 |
| 8/ 89 |
| 100/ 96.5 |
| 160/ 98 |
| 70 - 80 |
| 30 |
| 9/ 89 |
| 125/ 96.5 |
| 205/ 98 |
| 70 - 80 |
* Gmm: Maximum specific gravity of mix. (Rice Method) ** 67 percent specified lower limit VFA for 1-inch nominal maximum size mixture.
Table 9: Volumetric Design Requirements
| HMA design mixing and compaction temperatures |
| Provided by the Contractor as approved by the COR |
| Dust Proportion Range |
| 0.6 - 1.40 |
Voids in Mineral Aggregate (VMA) at Ndesign AASHTO R 35.9.2 using Gsb at SSD.
Equation based on percent of total mix.
12.5 % - 13.5 % for 1 inch
13.5 % - 14.5 % for ¾ inch
14.5 % - 15.5 % for ½ inch
15.5 % - 16.5 % for ⅜ inch
Hamburg Wheel Tracker
UDOT MOI 990
Maximum 10 mm impression at 20,000 passes.
PART 3 EXECUTION
| 3.1 | HMA |
| A. | Dry aggregate to an average moisture content of not more than 0.2 percent by weight. |
| 1. | May be verified by AASHTO T 255. |
| 2. | Adjust burners to avoid damage or soot contamination of the aggregate. |
| B. | Treat aggregate with hydrated lime. |
| 1. | Insure lime slurry equipment is operating at all times when using Method A. |
| a. | Cease production if hydrated lime slurry treatment is interrupted. |
| b. | COR may require marination of the aggregate/hydrated lime mixture in the stockpile, Method B, if production continues without hydrated lime slurry treatment. |
| C. | Coat with asphalt binder 100 percent of the particles passing and 98 percent of the particles retained on the No. 4 sieve. |
| 1. | May be verified by AASHTO T 195. |
| 2. | Discontinue operation and make necessary corrections if material is not properly coated. |
| D. | Maintain temperature of the HMA between identified limits for mixing and compaction as defined on Volumetric Mix Design Verification Letter. |
| 1. | Government rejects materials heated over the identified limits. |
| 2. | Remove all material rejected by the Government for overheating. |
| 3.2 | HMA PLANT |
| A. | Provide: |
| 1. | Positive means to determine the moisture content of aggregate. |
| 2. | Positive means to sample all material components. |
| 3. | Sensors to measure the temperature of the HMA at discharge. |
| 4. | The ability to maintain mix discharge temperature according to the mix design. |
| B. | Provide asphalt binder storage tanks that: |
| 1. | Calibrate tanks so the quantity of material remaining in the tank can be determined at any time. |
| 2. | Provide a positive means of sampling the asphalt binder from the tanks. |
| 3.3 | CEASE PRODUCTION |
| A. | Cease production when any two out of three consecutive lots meet one of the following criteria: |
| 1. | A net disincentive. |
| 2. | Air voids at Ndes averaged for each lot are less than 2.5 or greater than 4.5 percent |
| 3. | VMA at Ndes averaged for each lot are not within Target Value ± 1.25 percent. |
| B. | Submit a corrective action plan to the COR before production continues indicating the changes in production procedures that will be implemented to correct the deficiencies. |
| 3.4 | CONTRACTOR INITIATED CHANGES IN MIX DESIGN |
| A. | Changes in job mix gradation: |
| 1. | Submit a written request for a change in a job-mix gradation. Refer to this Section, article 1.5. |
| 3.5 | LABORATORY CORRELATION |
| A. | Perform split-sample, paired t-testing based on project quality control testing using UDOT LQP qualified lab. |
| 1. | Perform split-sample, paired t analysis on all mix acceptance tests and tests related to volumetric properties. |
| 2. | Perform paired t analysis as defined in the UDOT Materials Manual of Instruction, Appendix C. |
| 3. | Continue paired t-testing until at least two consecutive production days meet α = 0.05 for a two tailed distribution. |
| 3.6 | SURFACE PREPARATION |
| A. | Locate, reference, and protect all utility covers, monuments, curb and gutter and other components affected by the paving operations. |
| B. | Remove all moisture, dirt, sand, leaves, and other objectionable material from the prepared surface before placing the mix. |
| C. | Complete spot leveling before placing pavement courses. |
| 1. | Place, spread, and compact leveling mix on portions of the existing surface. |
| 2. | Fill and compact any localized potholes more than 1 inch deep. |
| 3. | Allow compacted mix to cool sufficiently to below 150 degrees F to provide a stable structural platform before placing additional lifts of HMA. |
| D. | Allow sufficient cure time for prime coat/tack coat before placing HMA. |
| 3.7 | SURFACE PLACEMENT |
| A. | Provide a 3:1 (horizontal to vertical) sloped edge adjacent to the next lane to be paved when full-width or Echelon paving is impractical and more than one pass is required. |
| B. | Adjust the production of the mixing plant and material delivery until a steady paver speed is maintained. |
| 1. | Provide continuous forward movement such that minimum temperature 10 feet behind paver is as follows. |
Table 10: Minimum Temperature, Degrees F
| Air Temp. Degrees F |
| Compacted Mat Thickness, in Inches |
| C. | Offset longitudinal joints 6 to 12 inches in succeeding courses. |
| 1. | Place top course joint within 1 ft of the centerline or lane line. |
| 2. | Tack the longitudinal edge before placing the adjacent pass if the previous pass has cooled below 175 degrees F. |
| D. | Offset transverse construction joints at least 6 ft longitudinally. |
| E. | Do not allow construction vehicles, general traffic, or rollers to pass over the uncompacted end or edge of freshly placed mix until the mat temperature drops to a point where damage or differential compaction will not occur. |
| F. | Taper the end of a course subjected to traffic at approximately 50:1 (horizontal to vertical). |
| 1. | Remove the portion of the pass that contains the tapered end before placing fresh mix. |
| 2. | Tack the contact surfaces before fresh mix is placed against the compacted mix. |
| G. | Use a motor grader, spreader box, or other approved spreading methods for projects under 180 yd2, irregular areas, or for miscellaneous construction such as detours, sidewalks, and leveling courses. |
| 3.8 | COMPACTION |
| A. | Use a small compactor or vibratory roller at structures in addition to normal rolling. |
| B. | Operate in a transverse direction next to the back wall and approach slab. |
| 3.9 | LIMITATIONS |
| A. | Do not place on frozen base or during adverse climatic conditions such as precipitation or when roadway surface is icy or wet. |
| B. | Use a release agent acceptable to the COR for all equipment and hand tools used to mix, haul, and place the HMA. |
| C. | Place between April 15, and October 15, and when the air temperature in the shade and the roadway surface temperature are above 50 degrees F. |
| 1. | The COR determines and provides written approval if it is acceptable to place outside the above limits. |
END OF SECTION
HOT-MIX ASPHALT FOR ROADS Page 4
