Section 32 12 16 Hot Mix Asphalt.pdf

SECTION 32 12 16

HOT-MIX ASPHALT (HMA) FOR ROADS

08/08

PART 1 GENERAL

1.1 SUMMARY (Not Applicable)

1.2 REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by basic designation only.

AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM)

ASTM C 88 (1990) Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate

ASTM C 127 (1988; R1993) Specific Gravity and Absorption of Course Aggregate

ASTM C 128 (1993)Specific Gravity and Absorption of Fine Aggregate

ASTM C 131 (1989) Resistance to Degradation of Small-Sized Course Aggregate by Abrasion and Impact in the Los Angeles Machine

ASTM C 136 (1993) Sieve Analysis of Fine and Coarse Aggregates

ASTM D 5 (1986) Penetration of Bituminous Materials

ASTM D 75 (1987; R1992) Sampling Aggregates

ASTM D 140 (1993) Sampling Bituminous Materials

ASTM D 242 (1985; R 1990) Mineral Filler for Bituminous Paving Mixtures

ASTM D 1559 (1992) Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus

ASTM D 2041 (1991) Theoretical Maximum Specific Gravity and Density of Bituminous Paving Mixtures

ASTM D 2172 (1995) Quantitatve Extraction of Bitumen from Bituminous Paving Mixtures

ASTM D 2726 (1996a) Bulk Specific Gravity and Density of Non-Absorptive Compacted Bituminous

Mixtures

ASTM D 3381 (1992) Viscosity-Graded Asphalt Cement for Use in Pavement Construction

ASTM D 3666 (1993) Minimum Requirement for Agencies Testing and Inspecting Bituminous Paving Materials

U.S. ARMY CORPS OF ENGINEERS, Sacramento District

PAM 415-1-2 Construction Control Manual; Sampling & Testing Construction Materials/Reporting Test Results

1.4 SUBMITTALS

Government approval is required for submittals with a "G" designation;

submittals not having a "G" designation are for information only. The following shall be submitted in accordance with Section 01330 SUBMITTAL

PROCEDURES:

SD-06 Test Reports

Aggregates; G, RE

Sources of aggregates shall be selected and notification thereof furnished to the Contracting Officer within 30 days after award of the contract.

Sampling and Testing

Copies of all laboratory and field test reports to the Contracting Officer in accordance with paragraph SAMPLING AND TESTING.

SD-05 Design Data

Composition of Mixture; G, RE

Mix designs for each type of blended material including a complete list of ingredients and admixtures. The applicable test reports shall verify that the mix has been successfully tested and meets design requirements.

1.4 PLANT, EQUIPMENT, MACHINES, AND TOOLS

1.5.1 Mixing Plants

Mixing plant shall be a weigh-batch, continuous-mix type or dryer drum type and operated so as to produce a mixture within the job-mix formula. The plant shall have a minimum capacity of 100 tons per hour.

1.5.2 Other Equipment

1.5.2.1 Spreaders

Bituminous-materials spreaders shall be self-propelled, capable of producing a finished surface conforming to the smoothness requirements specified hereinafter. The use of a spreader that leaves indentations or other objectionable irregularities in the freshly-laid mix is not permitted.

1.5.2.2 Blowers and Brooms

Blowers and brooms shall be of the power type suitable for cleaning the surface to be paved.

1.5.2.3 Saws

Saws shall be of the power type, capable of rapidly cutting pavement and trimming joints and edges of pavement.

1.5.2.4 Small Tools

Small tools available on the work shall consist of the following: rakes, lutes, shovels, tampers, smoothing irons, pavement cutters, portable heater for heating small tools, wood sandles and stilt sandals of standard type, and other small tools as may be required. A sufficient number shall be available at all times. The lutes shall be constructed of metal and shall consist of a plate or sheet 36 x 4 inches attached to a handle properly braced. Hand tampers shall weigh not less than 25 pounds and have a tamping face not larger than 50 square inches.

1.5.2.5 Straightedge

The Contractor shall furnish and maintain at the site, in good condition, one 10-foot straightedge for each bituminous paver. The straightedge shall be made available for Government use. Straightedges shall be constructed of aluminum or other lightweight metal and shall have blades of box-girder cross section with flat bottom reinforced to insure rigidity and accuracy.

Straightedges shall have handles to facilitate movement on the pavement.

1.5.3 Rollers

The minimum number of rollers for each spreader shall be one 2-axle tandem roller and one pneumatic-tired roller, with separate operator for each roller.

1.5.3.1 Steel Wheeled Rollers

Steel-wheel rollers shall be a self-propelled 2-axle tandem roller weighing not less than 10 tons. The rollers shall have adjustable wheel scrapers, water tanks, and sprinkling apparatus to keep the wheels sufficiently wet to prevent the bituminous mixture from sticking to the wheels. The rollers shall be capable of reversing without backlash and shall be free from worn parts. The roller wheels shall not have flat or pitted areas or projections that will leave marks in the pavement.

1.5.3.2 Pneumatic-tired Rollers

Pneumatic-tired rollers shall be self-propelled and shall consist of two axles on which are mounted multiple pneumatic-tired wheels in such manner that the rear group of wheels will not follow in the tracks of the forward group but spaced to give essentially uniform coverage with each pass.

Axles shall be mounted in a rigid frame provided with a loading platform or body suitable for ballast loading. Tires shall be smooth and capable of being inflated to at least 90 pounds per square inch. Construction of roller shall be such that each wheel can be loaded to a minimum of 4,500 pounds.

1.6 WEATHER LIMITATIONS

Bituminous course shall be constructed only when base course and existing pavement is dry. Unless otherwise directed, bituminous course shall not be constructed when temperature of the surface of existing pavement or base course is below 40 degrees F.

PART 2 PRODUCTS

2.1 AGGREGATES

Aggregates shall consist of crushed stone, crushed gravel, screenings, sand, and mineral filler. Aggregates shall have a satisfactory service record in bituminous pavement construction, and the source selected shall be approved by the Contracting Officer. The combined aggregates and mineral filler shall meet the requirements of subsequent paragraphs AGGREGATE GRADATION and COMPOSITION OF MIXTURE.

2.1.1 Coarse Aggregates

Coarse aggregate shall consist of clean, sound, durable particles meeting the following requirements:

a. Loss not greater that 40 percent after 500 revolutions when tested in accordance with ASTM C 131.

b. Loss not greater than 12 percent after five cycles of testing in accordance with ASTM C 88, using sodium sulfate.

c. At least 50 percent by weight of the aggregates retained on the No.

4 sieve shall have at least two fractured faces.

2.1.2 Fine Aggregates

Fine aggregate shall consist of clean, sound, durable, angular particles produced by crushing stone or gravel that meet the requirements for wear and soundness specified for coarse aggregates. This requirement shall apply to material before blending with natural sand when blending is necessary.

2.1.3 Mineral Filler

Material passing the No. 200 sieve shall be known as mineral filler, and shall conform to ASTM D 242.

2.1.4 Aggregate Gradation

The aggregate gradation as determined by ASTM C 117 and ASTM C 136 shall be the following:

Table 1. Aggregate Gradations

Sieve Percent by Weight Passing Designation Square-mesh Sieve (a)

Table 1. Aggregate Gradations

Sieve Percent by Weight Passing Designation Square-mesh Sieve (a)

3/4-inch 100 1/2-inch 95-100 3/8-inch 80-95 No. 4 59-66 No. 8 43-49 No. 30 22-27 No. 200 3-8

(a) Similar to the California Gradation for 1/2-inch maximum, coarse per section 39 of the California Department of Transportation Standard Specifications.

2.2 BITUMINOUS MATERIAL

Asphalt cement binder shall conform to AASHTO M 320 Performance Grade (PG) As an alternate, ASTM D 3381 Table 4, Viscosity Grade AR-4000 may be used.

Test data indicating grade certification shall be provided by the supplier at the time of delivery of each load to the mix plant. Copies of these certifications shall be submitted to the Contracting Officer. The supplier is defined as the last source of any modification to the binder. Samples of the asphalt cement specified shall be submitted for approval not less than 14 days before start of paving.

2.3 MIX DESIGN

The Contractor shall develop the mix design. The asphalt mix shall be composed of a mixture of well-graded aggregate, mineral filler if required, and asphalt material. The aggregate fractions shall be sized, handled in separate size groups, and combined in such proportions that the resulting mixture meets the grading requirements of the job mix formula (JMF). No hot-mix asphalt for payment shall be produced until a JMF has been approved. The hot-mix asphalt shall be designed using procedures contained in AI MS-02 and the criteria shown in Table 3. If the Tensile Strength Ratio (TSR) of the composite mixture, as determined by ASTM D 4867/D 4867M is less than 75, the aggregates shall be rejected or the asphalt mixture treated with an approved anti-stripping agent. The amount of anti-stripping agent added shall be sufficient to produce a TSR of not less than 75. If an antistrip agent is required, it shall be provided by the Contractor at no additional cost.

2.3.1 JMF Requirements

The job mix formula shall be submitted in writing by the Contractor for approval at least 14 days prior to the start of the test section and shall include as a minimum:

a. Percent passing each sieve size.

b. Percent of asphalt cement.

c. Percent of each aggregate and mineral filler to be used.

d. Asphalt performance grade or viscosity grade.

e. Number of blows of hammer per side of molded specimen.

f. Laboratory mixing temperature.

g. Lab compaction temperature.

h. Temperature-viscosity relationship of the asphalt cement.

i. Plot of the combined gradation on the 0.45 power gradation chart, stating the nominal maximum size.

j. Graphical plots of stability, flow, air voids, voids in the mineral aggregate, and unit weight versus asphalt content as shown in

AI MS-02.

k. Specific gravity and absorption of each aggregate.

l. Percent natural sand.

m. Percent particles with 2 or more fractured faces (in coarse aggregate).

n. Fine aggregate angularity.

o. Percent flat or elongated particles (in coarse aggregate).

p. Tensile Strength Ratio(TSR).

q. Antistrip agent (if required) and amount.

r. List of all modifiers and amount.

Table 2. Marshall Design Criteria

Test Property 75 Blow Mix

Stability, pounds minimum *1800

Flow, 0.01 inch 8-16

Air voids, percent 3-5

Percent Voids in 14.0 mineral aggregate VMA, (minimum)

TSR, minimum percent 75

* This is a minimum requirement. The average during construction shall be significantly higher than this number to ensure compliance with the specifications.

** Calculate VMA in accordance with AI MS-02, based on ASTM D 2726 bulk specific gravity for the aggregate.

PART 3 EXECUTION

3.1 SAMPLING AND TESTING

The testing laboratory and all field and laboratory testing personnel shall meet the requirements specified in ASTM D 3666. Aggregate sampling shall be performed in accordance with ASTM D 75. Bituminous materials shall be sampled in accordance with ASTM D 140. All 4-inch in diameter core samples shall be suitable to determine conformance with stability, density, thickness and other specified requirements. An approved core drill shall be used for cutting samples. The Contractor shall furnish all tools, labor, and materials for cutting samples, testing, and replacing the pavement where samples were removed, to the satisfaction of the Contracting Officer.

3.1.1 Testing Frequency

All sampling and control testing for construction of the pavement shall be performed by the Contractor in accordance with the requirements outlined in Chapter 4 of PAM 415-1-2 except that the metric versions of the referenced ASTM standards shall be used.

a. Asphalt: Collect a one-quart sample of asphalt and the refinery certification. Resample anytime the bituminous material source changes.

b. Aggregate: Collect a minimum of two 50 pound samples of mix aggregate from the hot bins; one sample at the beginning of each 8-hour shift and the other at mid-shift. Each 50 pound sample shall be split in half. The two half-samples (from the beginning and mid-shift) shall be labeled and packed separately and submitted to the Contracting Officer within 24 hours of sampling. Retain two half-samples for QC testing.

c. Hot Mix: Collect a minimum of two 70 pound samples of hot mix from the belt or transport truck; one sample at the beginning of each 8-hour shift and the other at mid-shift. Each 70 pound sample shall be split in half. The two half-samples (from the beginning and mid-shift) shall be labeled and packed separately and submitted to the Contracting Officer within 24 hours of sampling. Retain two half-samples for QC testing.

d. Core Specimens: Collect 1 set of 5 cores per each hot mix sample collected (if possible, 2 cores from the centerline of joints). Number cores and note the locations obtained on the as-built drawings. From each set, 2 cores shall be submitted to the Contracting Officer (preferably 1 core from a joint centerline). Retain remaining cores for quality control (QC) testing. Each of the QC core specimens require the following tests:

1) Core density shall be measured according to ASTM D 2726 and compared to the target density, which is the average laboratory density of specimens prepared according to ASTM D 1559 for each day's production.

2) Bitumen content shall be determined by the extraction method according to ASTM D 2172.

3) Thickness of each core shall be measured and recorded.

e. Smoothness Testing: Perform testing at 50 foot intervals along the section centerlines of the parking areas and access ways as specified in the paragraph SURFACE REQUIREMENTS.

3.2 TREATMENT OF UNDERLYING SURFACE

Prior to laying a bituminous course, the underlying surface shall be cleaned of loose and foreign matter by sweeping with power sweepers and hand brooms.

3.3 MIXING

Temperature of asphalt at time of mixing shall not exceed 325 degrees F when asphalt is added.

3.4 TRANSPORTATION OF BITUMINOUS MIXTURE

The bituminous mixture shall be transported from the mixing plant to the site in trucks having tight, clean, smooth bodies with a minimum coating of concentrated solution of hydrated lime and water to prevent adhesion of the mixture. Each load of mixture shall be covered with canvas or other suitable material to protect the mixture from the weather and to prevent loss of heat. Mixtures having temperatures greater than 325 degrees F, mixtures having temperatures less than 245 degrees F, or mixtures which foam or show indications of moisture will be rejected. Hauling over freshly laid material is not permitted.

3.5 PLACING

Contact surfaces of previously constructed pavement, curbs, manholes, or other structures shall be sprayed with a thin coat of bituminous tack coat in accordance with Section 02748 BITUMINOUS TACK AND PRIME COATS. The mechanical spreader shall be adjusted and its speed regulated so that the course being placed will be smooth and continuous without tears and pulling. The course will be of such depth that after compaction, the cross section, grade, and contour will be as shown on the drawings. In areas where the use of machine spreading is impractical, the mixture shall be spread by hand. Unless otherwise directed, placing shall begin on the high side of areas with a one-way slope or along the centerline of areas with a crowned section and shall be in the direction of the main traffic flow.

Placing of the mixture shall be as continuous as possible, and the speed of placing shall be adjusted to permit proper rolling.

3.6 COMPACTION OF ASPHALT MIXTURE

Compaction of asphalt mixture shall be accomplished by the steel wheel rollers and pneumatic-tired roller specified above.

3.6.1 Rolling

Rolling shall begin as soon after placing as the mixture will support the roller without undue displacement. Breakdown rolling shall consist of at least three coverages of a layer of asphalt mixture with a steel wheel roller, followed by at least three coverages with a pneumatic-tired roller. A coverage is defined to be as many passes in either direction as may be necessary to cover the entire width of lane with overlap between passes. Each layer shall be additionally compacted by a final rolling of not less than one coverage with a 2-axle tandem roller. The speed of the rollers shall not exceed 3 miles per hour and rolling shall be performed in such a manner to avoid cracking, shoving, or displacement of the hot mixture.

3.6.1.1 Vibratory Steel Wheeled Rollers

Use of vibratory steel wheel roller for breakdown and finish rolling is subject to prior approval. Vibratory roller shall be operated with the vibratory units off for finish rolling. The maximum weight of the vibratory roller shall not exceed 5 tons.

3.6.1.2 Mixture Density

The bituminous mixture shall be compacted to at least 95 percent of the density of the laboratory specimen of the same mixture subjected to 50 blows of a standard Marshall hammer on each side of the specimen. In areas not accessible to the roller the mixture shall be compacted with hot hand tampers. The compacted surface shall be smooth and free from roller marks, ruts, humps, depressions, or irregularities.

3.6.1.3 Compacted Thickness

The mixture shall be placed in one lift and compacted to the thicknesses indicated within the tolerances specified herein.

3.7 JOINTS AND EDGES

Joints between old and new pavements or between successive day's work, or joints that have become cold because of delay, shall be made to insure continuous bond between old and new sections of course. All joints shall have the same texture, density, and smoothness as other sections of course.

Contact surfaces of previously constructed pavements that have become coated with dust, sand or other objectionable material shall be cleaned by brushing or cut back with approved power saw, as directed. The surface against which new material is placed shall be sprayed with a thin, uniform coat of bituminous tack coat.

3.7.1 Transverse Joints

The roller shall pass over the unprotected end of freshly placed mixture only when placing of course is discontinued or when delivery of mixture is interrupted to the extent that unrolled material may become cold. In all cases, edge of the previously placed course shall be sawn back to expose an even, vertical surface the full thickness of the course.

3.7.2 Longitudinal Joints

Edges of previously placed strip that have cooled or are irregular, honeycombed, poorly compacted, damaged, or otherwise defective, and unsatisfactory sections of the joint shall be sawn back to expose clean, sound surface for full thickness of the course as directed.

3.7.3 Pavement Edges

Edges of pavement adjacent to shoulders shall be trimmed neatly to line.

An earth berm of selected material not less than one foot wide shall be placed against and to the full height of the pavement surface as soon as practicable after final rolling has been completed and pavement has sufficiently hardened.

3.8 PROTECTION OF PAVEMENT

No vehicular traffic shall be permitted on the pavement for at least 6 hours after final rolling.

3.9 SURFACE REQUIREMENTS

The finished surface shall not vary more than 1/4-inch over a 10-footspan, measured with a straightedge. The straightedge shall be furnished by the Contractor. Defective areas and any other areas that impound surface water shall be corrected by and at the expense of the Contractor. Straightedge testing shall be performed as a Contractor Quality Control requirement to demonstrate compliance.

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