Attachment 4 - SC HMA Division 400 - SOW.pdf

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May 2004 Asphalt Pavements 400-i

Table of Contents Section Page

401 HOT-MIX ASPHALT PAVEMENT .............................................................................401-1

401.1 DESCRIPTION OF WORK....................................................................................401-1

401.2 HMA QUALITY CONTROL / QUALITY ASSURANCE PROCEDURES ...............401-2

401.2.1 HMA QC / QA Program: Overview ...............................................................401-2

401.2.2 HMA Technician Certification Program.........................................................401-3

401.2.3 HMA Job Mix Formula ..................................................................................401-3

401.2.3.1 Design Responsibilities ........................................................................401-3

401.2.3.2 Submittals ............................................................................................401-4

401.2.3.3 Revisions..............................................................................................401-4

401.2.4 HMA Production Lot Numbering ...................................................................401-4

401.2.5 HMA Laboratory and Sampling Platform Requirements ...............................401-4

401.2.6 Notification of HMA Production and Acceptance Results .............................401-5

401.2.7 Quality Control Program (Contractor and SCDOT) ......................................401-5

401.2.7.1 HMA Quality Control Plan (Contractor) ................................................401-5

401.2.7.2 HMA Plant QC Samples and Tests (Contractor)..................................401-5

401.2.7.3 HMA Roadway QC Samples and Tests (Contractor and SCDOT) ......401-5

401.2.8 Acceptance Program (Contractor) ................................................................401-6

401.2.8.1 Basis of Payment .................................................................................401-6

401.2.8.2 HMA Plant Acceptance Samples and Tests.........................................401-6

401.2.8.3 HMA Roadway Acceptance Samples and Tests (Contractor)..............401-7

401.2.8.4 HMA Check Samples (Contractor) .......................................................401-8

401.2.9 Verification Program (SCDOT) .....................................................................401-8

401.2.9.1 General ................................................................................................401-8

401.2.9.2 HMA Plant Verification Samples and Tests..........................................401-8

401.2.9.3 HMA Roadway Verification Samples and Tests...................................401-9

401.2.10 Acceptance Procedures (SCDOT)..............................................................401-10

401.2.10.1 HMA Main-Line Paving ......................................................................401-10

401.2.10.2 HMA Non Main-Line Paving...............................................................401-10

401.2.10.3 HMA Low-Tonnage Paving ................................................................401-11

401.2.11 QC / QA Program Documentation Requirements .......................................401-11

401.3 AGGREGATE MATERIALS ................................................................................401-11

401.3.1 Sources of Aggregate Materials .................................................................401-11

400-ii Asphalt Pavements May 2004

Table of Contents (continued)

401.3.2 Aggregate Components of HMA Mixtures ..................................................401-12

401.3.2.1 Coarse Aggregate ..............................................................................401-12

401.3.2.2 Fine Aggregate...................................................................................401-12

401.3.2.3 Mineral Aggregate and Filler ..............................................................401-12

401.3.2.4 Crusher-Run Material .........................................................................401-13

401.3.3 Sampling Aggregate Materials....................................................................401-13

401.3.4 Aggregate Proportioning.............................................................................401-13

401.4 ASPHALT MATERIALS.......................................................................................401-14

401.4.1 Types of Asphalt Materials .........................................................................401-14

401.4.2 Properties of Asphalt Materials...................................................................401-15

401.4.3 Performance Graded Binders .....................................................................401-15

401.5 ANTI-STRIPPING MATERIALS ..........................................................................401-16

401.6 RECYCLED MATERIALS....................................................................................401-16

401.6.1 Recycled Asphalt Pavement (RAP) ............................................................401-16

401.6.1.1 SCDOT RAP Milling Projects .............................................................401-16

401.6.1.2 RAP Stockpiles ..................................................................................401-16

401.6.1.3 Recycled HMA Mixtures .....................................................................401-16

401.6.2 Asphalt Roofing Shingles............................................................................401-17

401.6.2.1 Source of Shingles .............................................................................401-17

401.6.2.2 Use of Shingles in HMA Mixtures.......................................................401-17

401.7 DESIGN OF HMA MIXTURES ............................................................................401-17

401.8 HMA MIX PRODUCTION AND HAULING ..........................................................401-18

401.8.1 General .......................................................................................................401-18

401.8.2 Plant and Production Considerations .........................................................401-18

401.8.3 Loading and Hauling Considerations..........................................................401-18

401.8.4 Production and Hauling Inspection – Summary..........................................401-19

401.8.4.1 Component Materials and Job Mix.....................................................401-19

401.8.4.2 Production and Hauling Equipment....................................................401-20

401.8.4.3 Production, Loading and Hauling Operations.....................................401-20

401.9 HMA MIX LAYDOWN AND COMPACTION ........................................................401-20

401.9.1 General .......................................................................................................401-20

401.9.2 Pre-Paving Considerations .........................................................................401-21

401.9.2.1 General ..............................................................................................401-21

May 2004 Asphalt Pavements 400-iii

401.9.2.2 Longitudinal Joint and Pavement Marking Plan .................................401-21

401.9.2.3 Contractor’s Paving Plan....................................................................401-21

401.9.2.4 Communications During Production and Paving................................401-21

401.9.2.5 Weather Considerations.....................................................................401-22

401.9.3 Equipment Considerations..........................................................................401-22

401.9.3.1 Paving Machines................................................................................401-22

401.9.3.2 Compaction Equipment ......................................................................401-23

401.9.3.3 Miscellaneous Equipment ..................................................................401-24

401.9.4 Surface Preparation Considerations...........................................................401-24

401.9.5 Delivery of Mix ............................................................................................401-26

401.9.5.1 General ..............................................................................................401-26

401.9.5.2 Mix Temperature ................................................................................401-26

401.9.5.3 Inspection Upon Delivery ...................................................................401-26

401.9.6 Placement Considerations..........................................................................401-27

401.9.7 Compaction Considerations........................................................................401-30

401.9.7.1 General ..............................................................................................401-30

401.9.7.2 Maximum Compacted Lift Thickness .................................................401-30

401.9.7.3 Factors Influencing Compaction.........................................................401-30

401.9.7.4 Temperature Susceptibility.................................................................401-30

401.9.7.5 Roller Pattern and Speed...................................................................401-31

401.9.7.6 Vibratory Roller Considerations..........................................................401-34

401.9.8 Other Considerations..................................................................................401-35

401.9.8.1 Joint Construction ..............................................................................401-35

401.9.8.2 Rumble Strips and Pavement Markers...............................................401-36

401.9.9 Laydown and Compaction Inspection – Summary .....................................401-36

401.9.9.1 Job Mix and Asphalt Prime and Tack Materials .................................401-36

401.9.9.2 Laydown and Compaction Equipment................................................401-36

401.9.9.3 Laydown and Compaction Operations ...............................................401-37

401.9.9.4 HMA Construction Troubleshooting Guidelines .................................401-38

401.10 POST-CONSTRUCTION CONSIDERATIONS ...................................................401-38

401.10.1 Acceptability of Final Surface, Crown and Grade .......................................401-38

401.10.2 Smoothness of Final Surface......................................................................401-38

401.10.3 Protection from Damage.............................................................................401-44

401.11 DOCUMENTATION AND PAYMENT CONSIDERATIONS ................................401-44

400-iv Asphalt Pavements May 2004

402 HOT-MIX ASPHALT INTERMEDIATE COURSE......................................................402-1

403 HOT-MIX ASPHALT SURFACE COURSE ...............................................................403-1

404 COLD-MIX ASPHALT INTERMEDIATE COURSE ...................................................404-1

405 COLD-MIX ASPHALT SURFACE COURSE.............................................................405-1

406 ASPHALT SURFACE TREATMENT – SINGLE TREATMENT ................................406-1

406.1 DESCRIPTION OF WORK....................................................................................406-1

406.2 PRECONSTRUCTION CONSIDERATIONS.........................................................406-1

406.3 INSPECTION DURING CONSTRUCTION ...........................................................406-2

406.3.1 Application of Asphalt Material .....................................................................406-2

406.3.2 Spreading of Aggregate................................................................................406-3

406.3.3 Determining Rate of Spread .........................................................................406-3

406.3.3.1 Asphalt Material ...................................................................................406-3

406.3.3.2 Aggregate Material ...............................................................................406-4

406.3.4 Rolling and Dragging ....................................................................................406-4

406.4 POST-CONSTRUCTION CONSIDERATIONS .....................................................406-4

406.5 DOCUMENTATION AND PAYMENT CONSIDERATIONS ..................................406-4

407 ASPHALT SURFACE TREATMENT – DOUBLE TREATMENT ..............................407-1

408 ASPHALT SURFACE TREATMENT – TRIPLE TREATMENT.................................408-1

409 OPEN-GRADED FRICTION COURSE......................................................................409-1

410 HOT-MIX ASPHALT THIN-LIFT SEAL COURSE.....................................................410-1

May 2004 Asphalt Pavements 401-1

Section 401 Hot-Mix Asphalt Pavement

401.1 DESCRIPTION OF WORK

A hot-mix asphalt (HMA) mixture is a combination of high-quality, sieve-graded coarse and fine aggregate materials, mineral filler, asphalt binder, admixtures (e.g., anti-stripping agent) and, as permitted by the Contract, recycled materials, such as recycled asphalt pavement, glass and shingles. These component materials must be selected, proportioned and mixed mechanically at an HMA plant based on a Job Mix Formula. One or more types of HMA courses may be specified for the pavement, and mix design, construction, acceptability and payment will depend on the type of HMA course to be constructed. The HMA Mix Design Technician will be responsible for:

• evaluating the suitability and gradation of aggregate material,

• designing the HMA mixture in an SCDOT-approved laboratory, and

• submitting the proposed material sources and Job Mix Formula for approval.

All component materials for the HMA mixture must be supplied from SCDOT-approved sources, as listed on SCDOT Approval Sheets. The design objective is to balance the properties of the mixture (e.g., workability vs. stability), while maintaining established parameters within specified limits (e.g., gradation, asphalt binder content). The properties of primary concern to the HMA Mix Design Technician include:

• moisture susceptibility – ability to resist stripping of asphalt binder;

• stability – ability to resist deformation under applied traffic loading;

• durability – ability to sustain original properties during in-service use and aging;

• permeability – ability to resist water and air entry;

• flexibility – ability to bend slightly under loading without cracking;

• workability – ability to be easily placed and compacted;

• fatigue resistance – ability to resist repeated traffic loading without failure; and

• skid resistance – ability to resist slipping and skidding of vehicular traffic.

Once the material sources and Job Mix Formula have been approved, the mixture will be produced at an HMA plant (e.g., batch plant, drum-mix plant). Prior to production, the HMA plant will be inspected for acceptability by the District Asphalt Manager or the Asphalt Materials Engineer, as appropriate. Scale certification, calibration of proportioning equipment, plant emissions and the following plant components are of primary concern:

• cold aggregate storage and feed system,

• aggregate heating and drying equipment,

• aggregate screening equipment,

• hot aggregate storage and weighing system,

• asphalt binder and admixture storage and metering system, 401-2 Asphalt Pavements May 2004

• mixing equipment, and

• storage silos.

At the start of production, the HMA plant will be calibrated to blend, heat and dry the required proportion of coarse and fine aggregate materials, add the proper quantity of asphalt binder and anti-stripping agent and thoroughly mix these component materials into an HMA mixture suitable for silo storage or immediate hauling, laydown and compaction. The HMA Quality Control Technician will be primarily responsible for monitoring compliance of the parameters established for the component materials and HMA mixture at the plant.

At the project site, the Asphalt Roadway Technicians will be responsible for ensuring that the HMA mixture is hauled, placed and compacted to meet the parameters established in the Contract Plans and Specifications for the HMA course (e.g., density, thickness, cross slope, grade). The Resident Construction Engineer and SCDOT Inspectors will be responsible for verifying Contract compliance and the acceptability of the HMA mixture delivered, placed and compacted. The HMA Quality Manager oversees both plant and roadway operations, troubleshoots production problems and is the Contractor’s primary contact with SCDOT personnel. Section 401 of this Manual presents significant discussion on topics that are important to the day-to-day responsibilities of both SCDOT and Contractor plant and roadway personnel. Specifically, the content in Section 401 applies to the following Sections of the Standard Specifications:

• Section 401 – Hot-Mix Asphalt Pavement,

• Section 402 – Hot-Mix Asphalt Intermediate Course,

• Section 403 – Hot-Mix Asphalt Surface Course,

• Section 404 – Cold-Mix Asphalt Intermediate Course,

• Section 405 – Cold-Mix Asphalt Surface Course,

• Section 409 – Open-Graded Friction Course, and

• Section 410 – Hot-Mix Asphalt Thin-Lift Seal Course.

401.2 HMA QUALITY CONTROL / QUALITY ASSURANCE PROCEDURES

HMA mixtures are typically used for base courses, intermediate courses and surface courses.

The Contract Plans and Specifications will designate the structure of the pavement required for the facility. This section describes the Department’s HMA Quality Control/Quality Assurance (QC/QA) procedures, including the HMA QC/QA Program; HMA Technician Certification Program; and quality control, acceptance and verification sampling and testing parameters, frequencies, methods and responsibilities.

401.2.1 HMA QC / QA Program: Overview

SCDOT administers all of its HMA construction projects under a statistical HMA QC/QA Program. Under this Program, SCDOT is responsible for establishing verification and acceptance parameters (e.g., samples, tests, target values, acceptance criteria, payment adjustment schedules), while the Contractor is responsible for controlling work and materials to ensure that the HMA pavement is constructed within established parameters. This contributes

May 2004 Asphalt Pavements 401-3 significantly to the production of a more consistent, higher quality pavement. Field acceptance criteria for HMA mixtures is typically based on:

• binder content (%AC),

• percent air voids (%AV),

• percent voids in mineral aggregate (%VMA), and

• the in-place density of the HMA mat.

Acceptance, rejection or acceptance at an adjusted price will be based on the acceptance criteria and the percentage of the Lot that is within specified limits. Where deficiencies are found, the Contractor is responsible for ceasing production until corrective action can be taken to bring production into compliance.

401.2.2 HMA Technician Certification Program

The HMA Technician Certification Program was jointly developed by SCDOT, FHWA and the Asphalt Paving Industry to ensure that personnel working under the HMA QC/QA Program are properly qualified to perform their respective duties. The HMA Technician Certification Task Force, composed of representatives from SCDOT, FHWA, Clemson University and the Asphalt Paving Industry, provides oversight; and the Department of Civil Engineering, Clemson University, administers the coursework, including formal classes and examination. By implementing this Certification Program, SCDOT can:

• improve the quality of both field and laboratory sampling and testing;

• enhance communications with the HMA paving industry; and

• increase HMA pavement performance and reduce overall life-cycle costs.

The South Carolina Certification Board, composed of one FHWA and eight SCDOT representatives, oversees the implementation of the HMA QC/QA Program and, as needed, the HMA Technician Certification Program.

Additional information regarding the HMA Technician Certification Program is available on the SCDOT website.

401.2.3 HMA Job Mix Formula

401.2.3.1 Design Responsibilities

The control parameters for each type of HMA mixture will be specified. The HMA Mix Design Technician (Level 2S), will be responsible for designing the mixture and preparing the Job Mix Formula in accordance with SC-T-80. The design will be prepared in a laboratory approved by the Research and Materials Engineer. A Job Mix Formula is not required for Sand Asphalt Base Course or Asphalt Aggregate Base Course; however, the asphalt binder content for the required HMA mixture will be verified and a Mix Design Form generated.

401-4 Asphalt Pavements May 2004

401.2.3.2 Submittals

Prior to production, the HMA Mix Design Technician will submit the proposed sources of component materials and the Job Mix Formula for the HMA mixture on the proper SCDOT Construction Forms to the Research and Materials Laboratory for approval. The Job Mix Formula will include the percentage of aggregate passing each required sieve, the percentage of asphalt binder not absorbed by aggregate and the percentage of anti-stripping agent in the HMA mixture. Note that a Job Mix Formula is specific to mixture type and HMA plant supplier and is to be approved by the Research and Materials Engineer for application on individual projects. There will need to be an approved Job Mix Formula submitted to the Resident Construction Engineer for each HMA mix used on any given project.

The Asphalt Materials Engineer will notify the HMA Mix Design Technician of any needed adjustments to the initial Job Mix Formula. Do not allow production to begin without written approval of the material sources and the Job Mix Formula from the Research and Materials Engineer.

401.2.3.3 Revisions

If the HMA Mix Design Technician or HMA Quality Manager determines that a revision to the HMA mixture design is necessary, a copy of the revision and supporting data will be forwarded to the District Asphalt Manager, Research Materials Engineer and District Materials Laboratory, when appropriate. SCDOT approval is necessary for any Job Mix Formula revision.

Implementation of the revision must occur between production lots. Pay particular attention to the Contract Specifications with respect to expiration period, number of revisions allowed and the requirements for a new Job Mix Formula.

401.2.4 HMA Production Lot Numbering

Once a series of Lot Numbers has been initialized on a project for a specific type of mixture supplied from a particular HMA plant, the Lot Numbers will run continuously until the type of mixture is no longer required for the project. Lot Numbers will be initialized at the beginning of the project and run continuously throughout the project, regardless of the need for a new Job Mix Formula for the same type of mixture from the same plant. There will be no calibration period. Lot Numbers begin immediately upon production.

401.2.5 HMA Laboratory and Sampling Platform Requirements

The Contractor is responsible for supplying and furnishing the HMA laboratory in accordance with SC-T-81 or SC-T-82, as appropriate, including all supplies necessary to perform quality control testing at the asphalt plant. When SC-T-75 is used, pay particular attention to compliance with the manufacturer’s recommendations for venting, calibrating, operating and maintaining the ignition oven. The Contractor is also responsible for supplying a platform high enough to allow sampling and inspection of the HMA mixture in truck beds. On an annual basis, the SCDOT Asphalt Materials Engineer will inspect the laboratory for acceptability and verify that the HMA Mix Design Technician has calibrated the laboratory equipment in accordance

May 2004 Asphalt Pavements 401-5 with SC-T-94 and, as needed, check the Technician’s calibration records. Non-compliance of laboratory and test equipment is grounds for halting production.

401.2.6 Notification of HMA Production and Acceptance Results

The HMA Quality Manager will notify the District Asphalt Manager prior to each day’s production so that SCDOT may arrange for verification testing. Failure to receive such notification is grounds for withholding payment for the day’s production. The HMA Quality Manager also is responsible for submitting the results of acceptance tests to the District Asphalt Manager within three production days after the completion of the mixture Lot. Non-compliance is grounds for halting production.

401.2.7 Quality Control Program (Contractor and SCDOT)

401.2.7.1 HMA Quality Control Plan (Contractor)

The Contractor is responsible for preparing and submitting a Quality Control Plan to the Research and Materials Engineer for approval. The Quality Control Plan will define the process control activities for HMA mixture design, production and placement, including inspection, sampling, testing, coordination and adjustment. During the project, verify that the Contractor operates within this Plan. Non-compliance is grounds for halting production.

401.2.7.2 HMA Plant QC Samples and Tests (Contractor)

The HMA Quality Manager will ensure that the HMA Quality Control Technician performs the necessary samples and tests. Note that these are minimum requirements and should be increased, as needed, to ensure compliance. The allowable limits of test parameters will be specified in the Contract. Non-compliance with minimum specified requirements is grounds for halting production.

401.2.7.3 HMA Roadway QC Samples and Tests (Contractor and SCDOT)

The HMA Quality Manager and Asphalt Roadway Technicians are responsible for compaction control, including compaction rollers and the rolling pattern. Verify the proper use of the density gauge to control the compaction process and document the results. The Resident Construction Engineer and Roadway Inspectors are responsible for verifying and documenting results of testing in the Daily Work Report and on SCDOT Form 400.04 – Daily Report of Asphalt Plant Inspection.

401-6 Asphalt Pavements May 2004

401.2.8 Acceptance Program (Contractor)

401.2.8.1 Basis of Payment

Only acceptance samples that have been obtained randomly in accordance with specified requirements will be used for computing daily pay factors. Any other type of sample, with the exception of quality control samples, will be performed for the exclusive use of the Contractor’s HMA Quality Manager.

401.2.8.2 HMA Plant Acceptance Samples and Tests

Prior to production, the District Asphalt Manager or Resident Construction Engineer, as assigned, will verify that the HMA Quality Manager has properly calibrated the HMA plant to the Job Mix Formula and field acceptance criteria. The HMA Quality Manager will ensure that HMA plant acceptance sampling and testing is performed. The allowable limits of test parameters will be specified in the Contract.

401.2.8.2.1 Binder Content Analysis (%AC)

The HMA Quality Control Technician will be responsible for determining %AC. Verify that SC-T- 62 is used to obtain an HMA mixture sample of the required size and that SC-T-72 is used to split the sample into acceptance, verification and referee samples. The acceptance sample should be tested for compliance and the verification and referee samples should be separately bagged, labeled with the proper SCDOT Sample Identification Card (see Appendix B) and stored. The Asphalt Materials Engineer will be responsible for determining the need to request the verification sample for testing under the Verification Program. The HMA Quality Control Technician must retain the referee sample until otherwise notified by the Asphalt Materials Engineer, and the disposition of samples should follow the specified disposal schedule. When an ignition oven is used to determine binder content, ensure that it is furnished and calibrated in accordance with SC-T-75. If acceptance and referee tests are not within allowable limits, check the HMA Mix Design Technician’s calibration log and, as needed, require re-calibration.

Complete SCDOT Form 400.01 – Ignition Oven Worksheet.

401.2.8.2.2 Voids Analysis (%AV, %VMA)

Verify that sample specimens are prepared and compacted in accordance with SC-T-66 and that %AV and %VMA are determined in accordance with SC-T-68. The acceptance sample should be tested for compliance and verification and referee samples, as appropriate, should be separately labeled using the proper SCDOT Sample Identification Card (see Appendix B) and stored. The Asphalt Materials Engineer will be responsible for determining the need to request the verification sample for testing under the Verification Program. The Technician must retain the samples until otherwise notified by the Asphalt Materials Engineer, and the disposition of samples should follow the specified disposal schedule. The maximum specific gravity (MSG) will be determined in accordance with SC-T-83. Percent air voids (%AV) will be determined by comparing the bulk specific gravity (BSG) of the compacted mixture to the mixture’s maximum specific gravity (MSG). Base course work does not require a %AV analysis.

May 2004 Asphalt Pavements 401-7

401.2.8.2.3 Washed Mixture Gradation Analysis

The HMA Quality Control Technician will be responsible for the washed mixture gradation analysis. Verify that acceptance tests for washed mixture gradation are performed for each sublot in accordance with SC-T-63, SC-T-76 and SC-T-92, as appropriate. Payment for asphalt aggregate base course will be based on the evaluation of each sublot, separately.

401.2.8.3 HMA Roadway Acceptance Samples and Tests (Contractor)

The Asphalt Roadway Technician is responsible for evaluating for acceptance the in-place density of the HMA mat in accordance with the minimum requirements. Note that these are minimum requirements and should be increased, as needed, to ensure compliance. The allowable limits of test parameters will be specified in the Contract.

401.2.8.3.1 In-Place Density Analysis (%Maximum Theoretical)

The Asphalt Roadway Technician is responsible for obtaining core samples for in-place density analyses at the locations determined by SCDOT using SC-T-101. This procedure is applicable to most intermediate courses and surface courses (see Section 403 of the Standard Specifications) placed at a rate equal to or greater than 140 pounds per square yard. Verify that the Asphalt Roadway Technician obtains one 6-inch core in accordance with SC-T-87 at each randomly selected location, as determined using SC-T-101. Each of these verification samples should be labeled using the proper SCDOT Sample Identification Card (see Appendix B) and stored, as specified. The Asphalt Materials Engineer will be responsible for determining the need to request the verification sample for testing under the Verification Program. The HMA Quality Control Technician must retain the samples until otherwise notified by the District Asphalt Manager or Asphalt Materials Engineer, and the disposition of samples should follow the specified disposal schedule.

401.2.8.3.2 In-Place Density Analysis (%Control Strip Target Density)

The Asphalt Roadway Technician is responsible for performing in-place density analyses using the density gauge, and the District Asphalt Manager or Resident Construction Engineer, as assigned, must witness this procedure. The density gauge must be approved by the Research and Materials Engineer and certified for use and transport by SCDHEC. Certification is the Contractor’s responsibility. Ensure that the Asphalt Roadway Technician adheres to the safety requirements associated with the use of the nuclear gauge and is prepared to mitigate and notify proper authorities in the event of a mishap. Verify that each Lot is subdivided corresponding to the number of density values required and that test locations within each sublot are randomly selected using SC-T-101. Density will be expressed as a percent of target density, as determined from a control strip constructed in accordance with SC-T-65.

Calculations will be carried out to the hundredths (0.01) and rounded to the nearest tenth (0.1) in accordance with AASHTO R 11.

401-8 Asphalt Pavements May 2004

401.2.8.4 HMA Check Samples (Contractor)

When an acceptance sample fails to meet specified limits for %AC, %AV, %VMA, Job Mix Formula gradation or dust-to-asphalt ratio, the HMA Quality Manager may opt to obtain another sample. This will be considered a check sample and will not be used to calculate pay factors. If two consecutive samples fail for any acceptance parameter, the HMA Quality Control Technician is required to immediately notify the District Asphalt Manager or Resident Construction Engineer. The HMA Quality Manager will analyze the problem and require adjustment to plant production. After adjustment, production will resume and the third truck load of mix will be sampled. The HMA Quality Manager will suspend further production until the test results on the sample has been obtained. If the test passes, production may resume; however, if the test fails, the mixture in the storage silo will be discarded and the plant cleared of all non-complying material. This procedure may be altered, as needed, by the Asphalt Materials Engineer.

401.2.9 Verification Program (SCDOT)

401.2.9.1 General

The District Asphalt Manager, Resident Construction Engineer and Roadway Inspectors should, on a regular basis, witness and document in the Daily Work Report and on SCDOT Form

400.03 – Daily Report of Asphalt Plant Inspection and SCDOT Form 400.04 – Daily Report of Asphalt Road Inspection the sampling and testing performed by the Contractor’s Technicians.

Although SCDOT verification tests will equal or surpass 10% of those required by the Contractor, SCDOT may elect to obtain additional samples or run additional tests for compliance verification. Within the first two days of production, at least one verification test each will be conducted for %AC, %AV, %VMA and in-place density. Under the Verification Program, SCDOT may select any or all of the Contractor’s retained verification samples for testing or run tests on independently selected random locations, as appropriate. SCDOT may use the Contractor’s test equipment or its own equipment, calibrated in accordance with SC-T-94. The HMA Quality Manager may opt to inspect SCDOT test equipment for concurrence. If non-compliance is observed through verification testing, SCDOT will immediately notify the HMA Quality Manager. The results of verification tests will be provided to the HMA Quality Manager. The District Asphalt Manager will investigate deficiencies and, if not immediately corrected, will request the HMA Quality Manager to halt production until corrective action is taken.

401.2.9.2 HMA Plant Verification Samples and Tests

401.2.9.2.1 Binder Content Analysis (%AC)

For %AC and maximum specific gravity (MSG), SCDOT will compare the results of testing the split samples made for acceptance and verification. If found within allowable difference, no further testing will be performed and the Contractor's acceptance test results will be used to compute the pay factor for the Lot of asphalt binder. If found to be outside allowable difference, the Research and Materials Engineer will test the referee sample and compare the result to the Contractor’s acceptance results. If found within allowable difference, no further testing will be

May 2004 Asphalt Pavements 401-9 performed and the Contractor’s acceptance test results will be used to compute the pay factor for the Lot of asphalt binder. If found to be outside allowable difference, then the result of testing the referee sample will be used in lieu of the Contractor’s acceptance test results in computing the pay factor for the Lot of asphalt binder. The District Asphalt Manager will immediately investigate (e.g., additional testing, observation of Contractor’s procedures) recurring problems and, as needed, halt production of the HMA mixture. Complete SCDOT Form 400.01 – Ignition Oven Worksheet.

401.2.9.2.2 Voids Analysis (%AV, %VMA)

For %AV and %VMA, SCDOT will compare the average value from testing verification samples to the average value obtained from the Contractor’s acceptance tests. The verification tests will be obtained from samples obtained from the same Lot as the Contractor’s acceptance samples.

A statistical analysis will be used, as specified, to compare the verification and acceptance values to determine if the Contractor’s acceptance values or additional testing is required to obtain values to compute the Lot pay factor for air voids. Follow the procedure specified in the Contract to perform this task. The District Asphalt Manager will immediately investigate (e.g., additional testing, observation of Contractor’s procedures) recurring problems and, as needed, halt production of the HMA mixture.

401.2.9.3 HMA Roadway Verification Samples and Tests

401.2.9.3.1 In-Place Density Analysis (%Maximum Theoretical)

This procedure applies to intermediate courses and all surface courses, unless otherwise specified. The District Asphalt Manager will compare the bulk specific gravity (BSG) value obtained from testing the SCDOT verification core sample with that obtained from the Contractor’s acceptance test. If the comparison is within allowable difference, no further testing will be required and the Contractor’s value will be used to compute the in-place density Lot pay factor; otherwise, the Research and Materials Engineer will test the referee sample and use the referee test value to compute the in-place density Lot pay factor. The District Asphalt Manager will immediately investigate recurring problems and, as needed, halt production of the HMA mixture.

401.2.9.3.2 In-Place Density Analysis (%Control Strip Target Density)

This procedure applies to Asphalt Aggregate Base Courses and specified surface courses. The District Asphalt Manager, Resident Construction Engineer or Roadway Inspector, as assigned, will obtain independent nuclear density readings for verification testing using the same type of density gauge as the Contractor. For each Lot selected for verification testing, SCDOT will use SC-T-101 to select 10 random locations within the Lot. SCDOT then will obtain one nuclear density value at each of these locations. A statistical analysis will be used, as specified, to comparing the verification and acceptance values to determine if the Contractor’s acceptance values or additional testing is required to obtain values to compute the Lot pay factor for in-place density. Follow the procedures specified in the Contract to perform this task. The District

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Asphalt Manager will immediately investigate (e.g., additional testing, observation of Contractor’s procedures) recurring problems and, as needed, halt production of the HMA

401.2.10 Acceptance Procedures (SCDOT)

401.2.10.1 HMA Main-Line Paving

Main-line paving refers to the construction of an HMA roadway pavement, including shoulders, ramps and acceleration/deceleration lanes. The Contract will define the following:

• acceptance procedures for the HMA mixture and mat;

• allowable deviations for HMA mixture properties in the Job Mix Formula;

• specification limits for test parameters;

• method for determining percent within limits; and

• methods for determining pay factors for base, intermediate and surface courses.

Only those tests specified as acceptance tests will be used in computing pay factors. The Contractor will be responsible for performing the required quality control and acceptance tests.

To assess acceptability, SCDOT will utilize and compare the Contractor’s acceptance tests with those obtained from SCDOT verification tests. As needed, the District Asphalt Manager, Asphalt Materials Engineer or Resident Construction Engineer may conduct additional testing and monitor the Contractor's procedures to assess problems and verify compliance.

401.2.10.2 HMA Non Main-Line Paving

Non main-line paving refers to the HMA courses that are not controlled by density requirements, which generally include patching, leveling, less than 8-foot widening, wedges and driveways.

The acceptance and pay factors for non main-line paving for %AC, %AV, and %VMA will be based on the absolute average difference from the target value for each acceptance characteristic. The Contract Specifications will define the following for non main-line paving:

• acceptance procedures for the HMA mixture and mat;

• method for determining average absolute difference; and

• method for determining pay factors for non main-line paving lots.

Only those tests specified as acceptance tests will be used in computing pay factors. The Contractor is responsible for performing the specified quality control and acceptance tests. To assess acceptability for payment, SCDOT will utilize and compare the Contractor’s acceptance test values with those obtained from SCDOT verification tests. As needed, the District Asphalt Manager, Asphalt Materials Engineer or Resident Construction Engineer may conduct additional testing and monitor the Contractor's procedures to assess problems and verify compliance.

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401.2.10.3 HMA Low-Tonnage Paving

Low-tonnage paving refers to production of a specific HMA mixture on a project as described in the Contract Specifications. The acceptance and pay factors for low-tonnage paving for %AC, %AV and %VMA will be based on the absolute average difference from the target value for each acceptance parameter. The Contract Specifications will define the following for low-tonnage paving:

• acceptance procedures for the HMA mixture and mat;

• specification limits for test parameters;

• method for determining percent within limits; and

• method for determining pay factors for low-tonnage lots (i.e., density and non-density).

Only those tests specified as acceptance tests will be used in computing pay factors. The Contractor is responsible for performing the specified quality control and acceptance tests. In-place density acceptance tests do not apply. To assess acceptability for payment, SCDOT will utilize and compare the Contractor’s acceptance test values with those obtained from SCDOT verification tests. As needed, the District Asphalt Manager, Asphalt Materials Engineer or Resident Construction Engineer may conduct additional testing and monitor the Contractor's procedures to assess problems and verify compliance.

401.2.11 QC / QA Program Documentation Requirements

The HMA Quality Manager will ensure that all quality control and acceptance inspections and test results are recorded and maintained daily on the appropriate SCDOT Construction Forms, including all observations, records of inspection, mixture adjustments and corrective actions.

The HMA Quality Manager will submit this documentation to the District Asphalt Manager, Asphalt Materials Engineer or Resident Construction Engineer, as appropriate, within 30 calendar days of completing the HMA work on the project. The District Asphalt Manager, Asphalt Materials Engineer or Resident Construction Engineer will provide the HMA Quality Manager with reproducible or printable copies of the appropriate SCDOT Construction Forms.

During prosecution of the work, verify that these records are being properly maintained and review the documents, as needed, to ensure compliance. All SCDOT personnel are required to maintain thorough and accurate project records in the Daily Work Report and appropriate SCDOT Construction Forms.

401.3 AGGREGATE MATERIALS

401.3.1 Sources of Aggregate Materials

Aggregate materials are commonly used for subbase, base course, Portland cement concrete, drainage features and HMA mixtures and are obtained from excavating pits or by dredging water courses. Explosives are commonly used to blast the rock material in roadway cuts and hillside or subsurface quarries, which will then be processed through crushers to reduce the size of the rock particles, alter their shape and create one or more fracture faces on each particle.

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401.3.2 Aggregate Components of HMA Mixtures

401.3.2.1 Coarse Aggregate

Pay attention to the type of HMA surface course to be constructed because the requirements for coarse aggregate will differ based on the type of HMA mixture specified. The coarse aggregate component may consist of crushed stone, gravel, slag, reprocessed aggregate from SCDOT RAP milling projects, or a combination of these materials. Coarse aggregate material must be supplied from a source listed on SCDOT Approval Sheet 2. Prior to production, properties such as density, abrasion loss, fractured faces, gradation, sodium sulfate soundness and maximum absorption will be evaluated by the Research and Materials Engineer to assess suitability.

Sampling and testing procedures SC-T-89, AASHTO T 96, AASHTO T 85 and AASHTO T 104 will be used to assess compliance. Other test procedures may be necessary as determined by the District Asphalt Manager or Research and Materials Engineer. To facilitate mix control, the source of aggregate material should not be changed during production.

401.3.2.2 Fine Aggregate

Depending on the type of HMA course to be constructed, the fine aggregate component of the HMA mixture may consist of sand; stone, slag or gravel screenings; or a combination of these materials. Fine aggregate material must be supplied from an approved SCDOT source, as listed on SCDOT Approval Sheet 1. The sampling and testing procedures SC-T-5 and SC-T-34 will be used to evaluate sand, and SC-T-5 and AASHTO T 176 will be used to evaluate screenings. The District Asphalt Manager or Research and Materials Engineer will ensure that the fine aggregate materials stockpiled at the plant are sampled and tested for compliance verification.

401.3.2.3 Mineral Aggregate and Filler

Depending on the gradation requirements of the type of HMA course to be constructed, the mineral aggregate required for the HMA mixture may be composed of fine aggregate material or a combination of coarse and fine aggregate materials. Note that the use of chrome slag is prohibited in HMA surface courses. To facilitate proportioning at the plant, the coarse and fine aggregate components will be stored separately in cold-feed bins, and the percent of each component, coarse and fine, will be based on the material retained or passing the No. 4 sieve, respectively. The District Asphalt Manager or Research and Materials Engineer will ensure that gradation and effective specific gravity of mineral aggregate are tested for compliance verification and that mineral filler conforms to the requirements of AASHTO M 17. Mineral filler is added for stabilization, but the quantity and type added can significant affect the mixture. If too much is added, the mixture may be difficult to roll and may become hard and brittle. During production, the source of mineral filler should not be changed and the amount added should be closely monitored. Note that mineral fillers must be kept dry in storage. If too much moisture is present, the mixture will look shiny and foamy, and the HMA will flatten in the truck bed.

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401.3.2.4 Crusher-Run Material

The use of crusher-run material in HMA mixtures is prohibited, with the exception of select low-volume HMA mixes. If it is evident or suspected that crusher-run material is causing segregation in the mix, require the producer to screen the material so that the coarse and fine components can be separately stored in cold-feed bins and combined in the proper proportion at the plant.

401.3.3 Sampling Aggregate Materials

Unless an aggregate sample is truly representative of the material to be tested, the test results may be useless. Sampling accuracy is just as important, if not more so, than testing accuracy.

Consider the following when obtaining aggregate samples from plant stockpiles:

1. Coarse Aggregate. Where coarse aggregate samples are obtained from plant stockpiles, the samples should be taken at random locations at or near the top of the stockpile, the base of the stockpile and at some intermediate point. When obtaining the sample, shove a board or piece of metal into the pile of material to prevent it from segregating while the sample is being removed.

2. Fine Aggregate. Where fine aggregate samples are obtained from plant stockpiles, first remove the dry layer of fines where most segregation occurs. Sample the wet or damp material underneath by inserting a sampling tube approximately 1.25 inches in diameter and 6 feet long into the material to obtain the sample.

It is difficult, but not impossible, to obtain accurate and representative samples from plant stockpiles. It is therefore good practice, where practical, to obtain aggregate samples from the cold-feed belt at the plant. Use caution when obtaining aggregate samples from the cold-feed belts. It is first necessary to stop the belt. Then, randomly select an area approximately 3 feet long for the sample. Use a board at each end of the sample to prevent segregation. Clean the entire sample area of the belt, and use a sample splitter to reduce the sample size, if necessary.

401.3.4 Aggregate Proportioning

Many methods are available to proportion aggregate materials to achieve the gradation for the HMA mixture; however, the most common method is trial and error used in conjunction with sound engineering judgment and experience. Generally, all that is needed for the procedure is a mechanical shaker, calculator, pencil and paper. The procedures are as follows:

• select the critical sieves for the blend and the initial proportion settings;

• calculate the blend on each sieve and check the blend against the specified limits; and

• adjust the proportion, as needed, to meet the specified limits.

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401.4 ASPHALT MATERIALS

401.4.1 Types of Asphalt Materials

The following describes the types of asphalt materials typically used for HMA mixtures, asphalt tack coats and asphalt prime coats:

1. Asphalt Binder. The term asphalt binder…