02550 Microsurfacing_Slurry Seal.doc

Pavements IDIQ

JCGU 09-1700

DIVISION 02 - SITE WORK

SECTION 02550 – MICROSURFACING

(SLURRY SEAL)

PART 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. All publications shall be the latest version/edition/revision of the documents listed below, in effect on the date of this solicitation, except where a date is given.

AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM)

ASTM C 136

Sieve Analysis of Fine and Coarse Aggregates

ASTM C 150

Portland Cement

ASTM D 75

Sampling Aggregate

ASTM D 140

Sampling Bituminous Materials

ASTM D 242

Mineral Filler for Bituminous Paving Mixtures

ASTM D 977

Emulsified Asphalt

ASTM D 2419

Sand Equivalent Value for Soils and Fine Aggregate

ASTM D 3910

Design, Testing, and Construction of Slurry Seal

ASTM D 4318

Liquid Limit, Plastic Limit, and Plasticity Index of Soils

STANDARD SPECIFICATION FOR CONSTRUCTION AND MAINTENANCE OF HIGHWAYS, STREETS AND BRIDGES, TEXAS DEPARTMENT OF TRANSPORTATION (TXDOT) JUNE 1, 2004

1.2 SUBMITTALS:

The following shall be submitted in accordance with Specification SECTION 01010:

Test Reports:

Sampling and testing shall be performed by an approved commercial testing laboratory or by facilities furnished by the Contractor. Copies of test results shall be furnished to the Contracting Officer within 24 hours of completion of tests.

Records:

Before the final statement is submitted, the Contractor shall submit to the Contracting Officer certified waybills and certified delivery tickets for all bituminous materials used in the construction of the pavement covered by the contract. The Contractor shall not remove bituminous material from storage until the initial outage and temperature measurements have been taken. The delivery or storage units shall not be released until the final outage has been taken.

1.3 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 seal will freeze before it has cured. Also, no slurry seal shall be placed if rain is probable before the slurry seal will have sufficient cure to prevent damage.

PART 2 – PRODUCTS:

2.1 CATIONIC POLYMER-MODIFIED ASPHALT EMULSION: Provide CSS-1P in accordance with Item 300.2.D, “Emulsified Asphalt” TXDOT or equal.

2.2 MINERAL AGGREGATE: Mineral aggregate shall consist of crushed stone, crushed gravel, or crushed slag and shall be clean, sound, and durable. Two or more aggregates from different sources 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 non-plastic. 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 or with Table I of Item 350.2.B of TXDOT.

TABLE I. AGGREGATE GRADATION

Sieve Size Percent Passing

3/8 inch

No. 4

90-100

No. 8

65-90

No. 16

45-70

No. 30

30-50

No. 50

18-30

No. 100 15-30

No. 200 5-15

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 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: 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 particle shape of crushed aggregate shall be essentially cubical. The quantity of flat and elongated particles in any sieve size shall not exceed 20 percent by weight, when determined in accordance with CRD-C 119.

2.3 MINERAL FILLERS: Hydrated lime or portland cement shall be added to the aggregate blend to meet the gradation requirements and to improve the stability 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 or Item 350.2.C of TXDOT.

2.4 WATER: Water for the slurry seal mixture shall be potable and free of harmful soluble salts.

2.6 SLURRY SEAL MIXTURE:

2.6.1 Composition: 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 or job mix formula and shall be furnished by the Contractor. Contractor shall also perform all other laboratory testing necessary to demonstrate compliance with these specifications. A copy of the test results and the mixture proportions shall be submitted to the Contracting Officer for approval at least 15 days prior to placement of the slurry seal mixture.

2.6.2 Properties: The slurry seal mixture 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 it is established that a satisfactory mixture meeting these requirements cannot be produced from the materials furnished the materials shall be rejected.

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 job-mix formula.

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

2.7.1 Mixing and Application Machine: The slurry mixing and application machine (slurry seal machine) shall be self-propelled, flow 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 pre-wetting the aggregate prior to mixing with the emulsion and thoroughly blending all ingredients

2.7.1.1 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 mineral filler is part of the aggregate blend.

2.7.1.2 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.

2.7.1.3 Storage Capacity of Machine: Sufficient machine storage capacity for a minimum of 5 tons of slurry seal shall be provided.

2.7.1.4 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 shall not be permitted. Burlap drags or other drags shall be provided. The drag shall be cleaned or replaced as needed to prevent accumulations or crust of slurry seal mix on the drag.

2.7.2 Bituminous Distributors: Bituminous distributors shall be self-propelled and shall be designed and equipped to distribute asphalt emulsion uniformly on various width of 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.

2.7.3 Pneumatic-Tired Rollers: Pneumatic-tired rollers shall be self-propelled and have wheels mounted on two axles in such a manner that the rear group of wheels will not follow in the tracks of the forward group. Tires shall be uniformly inflated to a minimum 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.

2.7.4 Cleaning Equipment: Cleaning equipment shall consist of power brooms, power blowers, power vacuums, hand brooms, and other equipment as needed. The equipment shall be suitable for cleaning the surface and cracks in the existing pavement in a safe manner.

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

PART 3 - EXECUTION

3.1 PREPARATION OF SURFACE: Prior to application of the slurry seal, the existing pavement surface shall be cleaned and accumulation of water removed. All cracks in the surface shall be cleaned by blowing out with compressed air sufficiently to remove all debris (vegetation, soil, rocks, etc.) within ½-inch of the surface. Cracks shall then be filled as follows: (1) Cracks larger than ¼-inch in width shall be filled by squeegeeing in a rich mixture of fine sand and asphalt emulsion and (2) Cracks larger than 1/8-inch but less than ¼-inch shall be filled by squeegeeing in asphalt emulsion. The final surface of the filled cracks shall be 1/8 to ¼ inch below the pavement surface. Any excess material shall be removed from the pavement surface. The above described work procedure is the same for Schedule B, CLIN item Cleaning and Sealing Joints and Cracks, TXDOT item 712 (without slurry seal).

3.1.1 Removal of Contamination, Traffic Paint, and Vegetation: All dust, dirt, oil, grease, fuel, loose or flaky traffic paint, vegetation, and other objectionable material shall be removed. All vegetation shall be removed completely, and these areas treated with a herbicide.

3.1.2 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 completely 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.

3.2 PREPARATION AND APPLICATION OF SLURRY SEAL:

3.2.1 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 elements shall be added. The slurry mixture shall show no signs of uncoated aggregate or premature breaking of emulsion when applied to the pavement surface. The total time of mixing shall not exceed 2 minutes.

3.2.2 Application: Sufficient quantities of the slurry seal mixture shall be fed into the spreader box such that a uniform and complete coverage of the pavement is obtained. The slurry seal machine shall be operated at such a speed that the amount of slurry in the spreader box shall remain essentially constant. The slurry shall be applied in such a manner that the minimum thickness will not be less than 3/16 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. Streaks shall not be left in the finished surface.

3.2.2.1 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 that 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.

3.2.2.2 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.

3.2.2.3 Hand Application: Areas which cannot be reached with the slurry seal machine shall be treated with hand squeegees to provide complete and uniform coverages. All such areas shall be tacked and fogged prior to placing slurry seal by hand.

3.3 ROLLING: As soon as the slurry seal has cured sufficiently to prevent displacement or pickup by wheel traffic (Normally within ½ hour), it shall be rolled with the pneumatic roller. Rolling shall continue until all ridges have been smoothed out and a uniform surface is obtained (Minimum of two passes).

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

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

3.6 APPURTENANCES: Appurtenances in the pavements which would otherwise be covered with asphalt slurry seal shall be suitably protected to prevent contamination with asphalt slurry. For example, concrete curbs and gutters, manholes, inlets, grates, etc. shall remain free of the asphalt slurry. Avoid such appurtenances or utilize masking to protect same. Masking materials shall be removed from the jobsite by the Contractor, when no longer needed.

3.7 SAMPLING AND TESTING

3.7.1 Sampling: Samples shall be obtained and tested by the Contractor at no expense to the Government. Sampling of aggregates shall be in accordance with the requirements of ASTM D 75. Sampling of bituminous material shall be in accordance with the requirements of ASTM D 140. Additional samples of materials shall be taken as required.

3.7.2 Testing: Materials shall be tested to establish compliance with the specified requirements. Quality control testing shall also be the responsibility of the Contractor and shall be performed by an approved commercial testing laboratory. At least 15 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. Additionally, for each day that slurry seal is placed, Contractor shall take at least one sample of slurry seal material from the discharge chute of the slurry seal machine. These samples shall be taken at a place and point in time selected by the Contracting Officer. Sample shall be sealed and initialed by the Contracting Officer or designated representative. Contractor shall have this sample tested for; 1) asphalt & cement content, 2) moisture content, and 3) aggregate gradation. Costs for all sampling and testing shall be at Contractor’s expense. Submit results of this testing to Contracting Officer for approval within 72-hours of sample collection. Slurry seal mixtures that fail to meet the mix design proportions and these specifications shall be rejected.

3.7.3 Calibration Test: The Contractor shall furnish all equipment, 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.

3.7.4 Test Section: Prior to applying the production slurry seal, a test section may be requested of at least 200-feet long and 20-feet wide shall be placed by the Contractor using the approved materials in the presence of the Contracting Officer or designated representative. The slurry seal shall be placed and rolled in accordance with specified requirements. Tests shall be made by the Contractor to determine the asphalt cement content, moisture content, and the aggregate gradation. Test results shall be submitted within 72 hours of sample taking. If the slurry seal thickness indications and the test indicates that the slurry seal test section does not conform to the specification requirements or the approved mix design, necessary adjustments shall be made, the defective slurry seal shall be removed, and the test section shall be repeated at no expense to the Government.

END OF SECTION

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