SECTION 02786 PAV 2008.doc

SECTION 02786

ASPHALT SLURRY SEAL

1 GENERAL

1.1 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 127

Specific Gravity and Absorption of Coarse Aggregate

ASTM C 128

Specific Gravity and Absorption of Fine Aggregate

ASTM C 136

Sieve Analysis of Fine and Coarse Aggregates

ASTM C 150

Portland Cement

ASTM D 75

Sampling Aggregates

ASTM D 140

Sampling Bituminous Materials

ASTM D 242

Mineral Filler for Bituminous Paving Mixtures

ASTM D 977

Emulsified Asphalt

ASTM D 1073

Fine Aggregate for Bituminous Paving Mixtures

ASTM D 1250

Petroleum Measurement Tables

ASTM D 2397

Cationic Emulsified Asphalt

ASTM D 2419

Sand Equivalent Value of Soils and Fine Aggregate

ASTM D 2995

Determining Application Rate of Bituminous Distributors

ASTM D 3910

Design, Testing, and Construction of Slurry Seal

ASTM D 4318

Liquid Limit, Plastic Limit, and Plasticity Index of Soils

ASTM D 4791

Flat or Elongated Particles in Coarse Aggregate

INTERNATIONAL SLURRY SURFACING ASSOCIATION (ISSA)

ISSA TB-102

Mixing, Setting and Water Resistance Test to Identify "Quick-Set" Emulsified Asphalts

1.2 MEASUREMENT

Bituminous material and aggregate to be paid for will be the measured quantities used in the accepted work.

1.2.1 Quantity of Bituminous Material

Amount of bituminous material to be paid for shall be measured in the number of gallons of the material used in the accepted work corrected to gallons at 60 degrees F, in accordance with ASTM D 1250. A coefficient of volumetric expansion of 0.00025 per degree F shall be used for asphalt emulsions.

1.2.2 Aggregate and Filler

Amount of aggregate and filler to be paid for shall be the number of dry 2,000 pound tons of each placed and accepted in the completed work. Quantities of the aggregate blend shall be based on a specific gravity of 2.70, as determined in accordance with the Apparent Specific Gravity paragraphs in ASTM C 127 and ASTM C 128. Correction in tonnage of the aggregate blend shall be made to compensate for the difference in tonnage of the blend used in the project, when specific gravities of aggregate blend used are more than 2.75 or less than 2.65. Tonnage paid for shall be the number of tons used, proportionately corrected for specific gravities, using 2.70 as the base correctional factor.

1.3 PAYMENT

Quantities of bituminous material, aggregate, and filler, determined in paragraph MEASUREMENT, will be paid for at the respective contract unit prices. Such payment shall constitute full compensation for all operations necessary to complete the specified work.

1.4 SUBMITTALS

Government approval is required for submittals with a "GA" designation; submittals having an "FIO" designation are for information only. The following shall be submitted in accordance with Section 01330 SUBMITTAL PROCEDURES:

SD-01 Data Mixing and Application Machine; GA. Job Mix Formula (JMF)[GA].

Details and data on the make, type, and capacity of the slurry seal machine. A copy of the mixture proportions.

SD-14 Samples Sampling and Testing; GA.

At least 30 days prior to placement of the slurry mixture, representative samples in the following quantities:

Aggregate or aggregates which can be combined to form the specified gradation: 100 pounds.

Asphalt emulsion: 2 gallons.

Mineral filler (if required): 10 pounds.

Additional samples of materials, as required.

SD-09 Reports Sampling and Testing; GA.

A quality control report within 24 hours of each day of construction. The quality control test shall include tabulated test results showing asphalt cement content, moisture content, and aggregate gradation of all samples tested. A diagram identifying the location of each slurry sample taken.

SD-13 Certificates Materials; GA.

The material supplier's statement that the supplied material meets specified requirements. Each certificate shall be signed by an official authorized to certify in behalf of material supplier and shall identify quantity and date or dates of shipment or delivery to which the certificates apply.

1.5 DELIVERY AND STORAGE

Materials delivered to the site shall be inspected for contamination and damage, unloaded, and stored with a minimum of handling. Aggregates and mineral fillers shall be stockpiled to prevent segregation, contamination, or accumulation of excess moisture. Emulsion shall be stored preventing freezing, entrance of water, or breaking of the emulsion. Materials that are determined by the Contracting Officer to be contaminated, segregated, or damaged, or which fail to meet specification requirements shall be removed from the job site and replaced at no additional cost to the Government.

1.6 WAYBILLS AND DELIVERY TICKETS

Copies of waybills and delivery tickets shall be submitted during the progress of the work. Before the final statement is allowed, the Contractor shall file with the Contracting Officer certified waybills and delivery tickets for all materials used in the work covered by this section. The Contractor shall not remove bituminous material from tank cars or storage tanks until measurements of the remaining quantity have been determined.

1.7 WEATHER LIMITATIONS

Slurry seal shall not be applied if air or pavement temperatures are below 60 degrees F or if there is any possibility that the slurry will freeze before it has cured. No slurry seal shall be placed if rain is probable before the slurry seal will have sufficiently cured to prevent damage.

1.8 EQUIPMENT

Machines, tools, and equipment used in the performance of the work will be approved by the Contracting Officer before the work is started and shall be maintained in satisfactory condition.

1.8.1 Mixing and Application Machine

The slurry mixing and application machine (slurry seal machine) shall be a self-propelled, continuous flow mixing unit capable of accurately delivering a predetermined proportion of aggregate, water, mineral filler, and asphalt emulsion to the mixing chamber and of discharging the thoroughly mixed product on a continuous basis. The machine shall be capable of prewetting the aggregate immediately prior to mixing with the emulsion. The mixing unit of the machine shall be capable of thoroughly blending all ingredients.

1.8.1.1 Fines Feeder

The slurry seal machine shall be equipped with a fines feeder that provides an accurate metering device or method to introduce a predetermined proportion of mineral filler into the mixer at the same time and location as the aggregate. The fines feeder shall be used whenever added mineral filler is a part of the aggregate blend.

1.8.1.2 Fogging

The slurry seal machine shall be equipped with a water pressure system and fog-type spray bar adequate for complete fogging of the pavement surface. The spray bar shall be so mounted on the mixing machine that fogging will immediately precede application of the slurry seal mix.

1.8.1.3 Storage Capacity on Machine

The hoppers shall contain sufficient storage capacity of all materials required to produce a minimum of 5 tons of slurry seal.

1.8.1.4 Slurry Spreading Equipment

A variable-width mechanical-type squeegee spreader box shall be attached to the slurry seal mixing machine. The spreader box shall be equipped and maintained with flexible material in contact with the pavement surface to prevent loss of slurry seal from the spreader box on varying grades and crown. The spreader box shall be capable of adjustments to assure uniform spread. The spreader box shall be equipped for lateral distribution of the slurry mixture within the spreader box regardless of spreader box width or crown or bank of the pavement surface. The spreader box shall be kept clean, and buildup of asphalt and aggregate on either squeegee or spreader box will not be permitted. At the Contractor's option, burlap drags or other drags may be provided. If used, the drag shall be cleaned or replaced as needed to prevent accumulations or crust of slurry seal mix on the drag.

1.8.2 Bituminous Distributors

Bituminous distributors for applying tack coat shall be self-propelled and shall be designed and equipped to distribute asphalt emulsion uniformly on various widths of the pavement surface at readily determined and controlled rates ranging from 0.05 to 2.00 gallons per square yard, with a pressure range of 25 to 75 psi. Allowable variation from any specified rate shall not exceed 5.0 percent.

1.8.3 Pneumatic-Tired Rollers

Pneumatic-tired rollers shall be self-propelled and have wheels mounted on two axles so that the rear group of wheels will not follow in the tracks of the forward group. Tires shall be uniformly inflated to a minimum tire pressure of 50 psi. Rollers shall be equipped with water tanks and sprinkler apparatus which shall be used to keep the wheels damp and prevent adherence of bituminous materials to the wheels.

1.8.4 Cleaning Equipment

Cleaning equipment shall consist of power brooms, power blowers, power vacuums, air compressors, hand brooms, and other equipment as needed. The equipment shall be suitable for cleaning the surface and cracks in the existing pavement.

1.8.5 Hand Tools

Hand tools shall consist of hand squeegees, shovels, and other equipment as necessary to perform the work.

2 PRODUCTS

2.1 BITUMINOUS MATERIAL

Bituminous material shall be emulsified asphalt conforming to ASTM D 977, Type SS-1 or SS-1h; or to ASTM D 2397, Type CSS-1 or CSS-1h; or to quick set mixing grade ISSA TB-102.

2.2 MINERAL AGGREGATE

Mineral aggregate shall consist of crushed stone, crushed gravel, or crushed slag. The portion of materials retained on the No. 4 sieve shall be known as coarse aggregate; the portion passing the No. 4 sieve and retained on the No. 200sieve as fine aggregate; and the portion passing the No. 200 sieve as mineral filler. Two or more aggregates from different sources or of different types may be blended to produce the required gradation. When two or more aggregates are so blended, each shall meet the quality requirements stated herein. When tested in accordance with ASTM D 4318, aggregate shall be nonplastic. The aggregate shall have a sand equivalent of 45 or greater when tested in accordance with ASTM D 2419. Aggregate shall conform to the gradation given in Table I when tested in accordance with ASTM C 136.

TABLE I. AGGREGATE GRADATION

Percent Passing

Sieve Size Gradation 1 Gradation 2 Gradation 3

3/8-in. 100

No. 4 70-90 100

No. 8 45-70 78-95 100

No. 16 28-50 55-80 70-94

No. 30 19-34 35-60 45-73

No. 50 12-24 20-40 25-50

No. 100 7-16 10-22 10-25

No. 200 4-12 4-12 4-14

2.2.1 Crushed Gravel

Crushed gravel retained on the No. 4 sieve and each coarser sieve shall contain at least 75 percent by weight of crushed pieces having two or more fractured faces with the area of each face equal to at least 75 percent of the smallest mid-sectional area of the piece. When two fractures are contiguous, the angle between planes of fractures shall be at least 30 degrees to count as two fractured faces.

2.2.2 Fine Aggregate

The fine aggregate shall conform to the physical and supplementary requirements of ASTM D 1073, except as modified herein. Fine aggregate produced by crushing gravel shall have at least 90 percent by weight of crushed particles having two or more fractured faces in the portion retained on the No. 30 sieve. This requirement shall apply to material before blending with other aggregates when blending is necessary.

2.2.3 Particle Shape of Crushed Aggregate

The quantity of flat and elongated particles in any sieve size shall not exceed 20 percent by weight, when determined in accordance with ASTM D 4791.

2.3 MINERAL FILLERS

Mineral fillers, such as hydrated lime or Portland cement, shall be added to the aggregate blend, if needed, to meet the gradation requirements or to improve the workability of the slurry seal mixture. Mineral fillers shall meet the gradation requirements of ASTM D 242. Portland cement shall conform to ASTM C 150, Type I or II.

2.4 WATER

Water for the slurry seal mixture shall be potable.

2.5 TACK COAT

Tack coat shall consist of one part emulsified asphalt and up to three parts water. The same type and grade of asphalt emulsion shall be used in the tack coat as used to make slurry seal, unless otherwise directed.

2.6 SLURRY SEAL MIXTURE

2.6.1 Job Mix Formula (JMF)

[The exact proportions of asphalt emulsion, aggregate, water, and mineral filler to be used in the preparation of the slurry seal shall be determined by laboratory mix design in accordance with ASTM D 3910 and shall be furnished by the Contractor. A copy of the JMF shall be submitted to the Contracting Officer for approval 30 days before the slurry seal mixture is placed.] [The Contracting Officer will select the proportions for the JMF.]

2.6.2 Properties

The slurry seal JMF shall possess workability and stability properties consistent with the application requirements of paragraph PREPARATION AND APPLICATION OF SLURRY SEAL and, in addition, shall meet the consistency test requirement of a 1 inch flow and the wet track abrasion test requirement of not more than 75 grams per square foot abrasion loss when tested in accordance with ASTM D 3910. If quick set emulsion is used, the slurry seal mixture shall pass when using project aggregate and tested in accordance with ISSA TB-102. If it is established that a mixture meeting these requirements cannot be produced from the furnished materials, these materials shall be replaced.

2.6.3 Setting Time

The mixture shall attain an initial set in not less than 15 minutes nor more than 12 hours when tested in accordance with ASTM D 3910. The setting time may be regulated by the addition of mineral fillers or chemical agents provided that provision for their inclusion is contained in the JMF.

3 EXECUTION

3.1 PREPARATION OF SURFACE

Prior to application of the slurry seal, the existing pavement surface shall be cleaned, accumulation of water removed, and unsatisfactory areas repaired. As directed, weak areas or soft spots indicated by alligator cracking, pot holes, or any cracking indicating a structural deficiency shall be removed and replaced to match the grade of the existing pavement section. Cracks in the surface not due to structural deficiencies shall be cleaned by blowing out with compressed air. Cracks larger than 1/4 inch in width shall be filled by squeegeeing in a slurry of fine sand and asphalt emulsion. Cracks larger than 1/8 inch but less than 1/4 inch in width shall be filled with asphalt emulsion. The final surface of the filled cracks shall be 1/8 to 1/4 inch below the pavement surface. Any excess material shall be removed from the pavement surface prior to placement of the slurry seal.

3.1.1 Removal of Contamination, Traffic Paint, and Vegetation

Dust, dirt, oil, grease, fuel, loose or flaky traffic paint, vegetation, and other objectionable material shall be removed from the pavement surface. Grease-contaminated and oil-contaminated areas which cannot be cleaned shall be removed and replaced with new bituminous pavement. All vegetation shall be completely removed, and these areas treated with an approved herbicide.

3.1.2 Preparation and Application of Tack Coat

3.1.2.1 Calibration of Bituminous Distributor

The Contractor shall furnish all equipment, materials, and labor necessary to calibrate the bituminous distributor. Calibration shall be made with the approved job material and prior to applying the tack coat material to the prepared surface. Calibration of the bituminous distributor shall be in accordance with ASTM D 2995.

3.1.2.2 Tack Coat Application

After the surface has been prepared for the slurry seal, a tack coat shall be applied with a bituminous distributor at the rate of 0.05 to 0.10 gallon per square yard of surface. The tack coat shall be allowed to cure before the slurry seal is applied.

3.1.3 Wetting Pavement Surface

Immediately prior to application of the slurry seal, the surface of the pavement and all crack faces shall be moistened with a fog spray of water from the spray bar on the slurry seal machine. No free water shall be on the surface of the pavement following the fog spray. The rate of application of the fog spray shall be adjusted during the day to suit pavement temperatures, surface texture, humidity, and dryness of the pavement surface.

3.1.4 Trial Application

Prior to apply the slurry seal, a test section at least 200 feet long and 20 feet wide shall be placed by the Contractor using the approved materials. The slurry seal shall be placed and rolled in accordance with the specified requirements. Tests shall be made to determine the asphalt cement and moisture contents and the aggregate gradation. If test results are satisfactory, the test section shall remain in place as part of the completed slurry seal. If tests indicate that the slurry seal does not conform to specification requirements, necessary adjustments to the slurry seal machine and application procedures shall be made immediately, and additional test sections shall be constructed and samples shall be taken and tested for conformance with specification requirements. If tests indicate that the slurry seal does not conform to specification requirements, the test section shall be removed at no cost to the Government, and the material disposed of off-site. In no case shall the Contractor start full production of slurry seal without approval.

3.2 PREPARATION AND APPLICATION OF SLURRY SEAL

3.2.1 Calibration of Slurry Seal Machine

The slurry seal machine shall be calibrated in the presence of the Contracting Officer to assure that it will produce and apply a mixture which conforms to the JMF. Commercial slurry seal machines shall be provided with a method of calibration by the manufacturer. Because of varying mechanical properties, each machine may have a different calibration procedure. However, a calibration method based on a revolution counter on any shaft which is mechanically interlocked with the emulsion pump, water pump, fines feeder, and the aggregate conveyor can be used to determine the relative quantities of each component per revolution for various gate openings, metering, valve opening, or sprocket sizes. The slurry seal machine shall be calibrated with the project materials prior to the start of work, or whenever there is a change in materials.

3.2.2 Preparation

The slurry seal shall be mixed and applied with a slurry machine. A minimum amount of water shall be used as necessary to obtain a workable and homogenous mixture. The mixture shall be of proper consistency with no segregation when deposited on the surface of the pavement and no additional materials shall be added to the mixture. The slurry mixture shall show no signs of un-coated aggregate or premature breaking of emulsion when applied to the pavement surface. The total time of mixing shall not exceed 2 minutes.

3.2.3 Application

Sufficient quantities of the slurry seal mixture shall be fed into the spreader box to obtain a uniform and complete coverage of the pavement. The slurry seal machine shall be operated at a speed that will keep the amount of slurry in the spreader box essentially constant. The slurry shall be applied maintaining the minimum thickness at not less than 1/8 inch. When multiple applications are required, each application shall be thoroughly cured before another application is placed. No oversized aggregate particles shall be allowed in the slurry seal mixture, and no buildup of cured slurry seal mix shall be allowed to collect in the spreader box. The finished surface shall be left without streaks.

3.2.3.1 Joints

The longitudinal joint between adjacent lanes shall have no visible lap, pinholes, or uncovered areas. Thick spots caused by overlapping shall be smoothed immediately with hand squeegees before the emulsion breaks. Overlaps which occur at transverse joints shall also be smoothed before the emulsion breaks, so that a uniform surface is obtained which contains no breaks or discontinuities. Whenever possible, joints should be made while the slurry seal mixture applied in the first pass is still semi-fluid and workable. If operations preclude fresh working of joints, the previously laid pass shall be sufficiently cured in order to support the spreader box without scarring, tearing, or scraping.

3.2.3.2 Stability of Slurry Mixture

The slurry seal mixture shall possess sufficient stability so that segregation or premature breaking of emulsion in spreader box does not occur. The mixture shall be homogenous following mixing and spreading, shall be free of bleeding of water or of emulsion, and free of segregation of emulsion and aggregate fines from the coarser aggregate fraction.

3.2.3.3 Hand Application

Areas which cannot be reached with the slurry seal machine shall be treated with hand squeegees to provide complete and uniform coverage. All areas shall be tacked and fogged prior to placing slurry seal by hand. Close attention should be given during hand squeegee spreading of slurry seal mixture. Overworking will sometimes cause partial breaking of the emulsion before the final spreading is completed; this results in a non-uniform material that will have poor appearance and low durability.

3.3 ROLLING

As soon as the slurry seal has cured, sufficiently to prevent displacement or pickup by wheel traffic, it shall be rolled with the pneumatic roller. A minimum of 5 coverages shall be applied, and, when required, rolling shall continue until all ridges have been smoothed out and a uniform surface is obtained.

3.4 CURING

Completed slurry seal shall be protected from traffic by barricades and markers until the slurry seal has cured. Areas which are damaged by traffic or from other causes shall be repaired by the Contractor at no cost to the Government.

3.5 SAMPLING AND TESTING

3.5.1 Sampling

Samples of slurry seal materials shall be furnished by the Contractor at no expense to the Government. Sampling of aggregates, unless otherwise specified, shall be in accordance with the requirements of ASTM D 75. Sampling of bituminous material, unless otherwise specified, shall be in accordance with the requirements of ASTM D 140. Additional samples of materials shall be furnished as required.

3.5.2 Testing

Materials shall be tested to establish compliance with the specified requirements. Quality control testing shall be the responsibility of the Contractor and shall be performed by an approved independent commercial testing laboratory or by Contractor testing, subject to approval. At least 30 days prior to the use of materials in the work, certified copies of the test results specified herein and in referenced publications shall be submitted for approval. In addition for each day that slurry seal is placed, a minimum of one sample of slurry seal shall be taken from the discharge chute of the slurry seal machine and tested to determine asphalt cement content, moisture content, and aggregate gradation. Slurry seal mixture that fails to meet the mix design proportions shall be rejected.

3.5.3 Calibration Test

The Contractor shall furnish all equipment and materials and labor necessary to calibrate the slurry seal machine. All calibrations shall be made with the approved job materials and prior to applying the slurry seal materials to the prepared surface. A copy of the calibration test results shall be submitted before the slurry seal machine is used on the job.

3.6 CLEANUP

On completion of work, all trash, discarded slurry seal material, or other refuse shall be collected and removed from the site and disposed of as approved by the Contracting Officer.

END OF SECTION

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