Sealcoating Specifications

Airport Sealcoating Specifications Item P-630

ITEM P-630 REFINED COAL TAR EMULSION WITHOUT ADDITIVES, SLURRY SEAL SURFACE TREATMENT

DESCRIPTION

This surface treatment is for apron locations serving airplanes 60,000 lbs (27216 kg) or less that need a fuel resistant surface treatment.

Consult local and state environmental/safety regulations.  Many locations prohibit the use of coal tar products. The Engineer must verify the selected materials comply with federal, state, and local authority requirements.

630-1.1 This item shall consist of a mixture of emulsified coal tar, mineral aggregate, and water properly proportioned, mixed, and spread on an asphalt pavement surface, including airport pavements serving [   small   ] airplanes [   12,500 lbs (5670 kg) or less,    ] roads, and other general applications.  The purpose of this refined coal tar emulsion product is to provide a fuel-resistant surface where pavements are subjected to fuel spills. The application of the surface treatment shall be in accordance with these specifications and shall conform to the dimensions shown on the plans or as directed by the Resident Project Representative (RPR).

630-1.2 General. This item shall consist of a mixture of refined coal tar emulsion, mineral aggregate, and water properly proportioned, mixed, and applied as a slurry seal on new or existing (aged) asphalt concrete pavement.

MATERIALS

630-2.1 Refined coal tar emulsion. A refined coal tar emulsion prepared from a high temperature refined coal tar conforming to the requirements of ASTM D490 for grade 11-12. The use of oil and water gas tar is not allowed. Base refined coal tar emulsion must conform to all requirements of ASTM D5727.

The Contractor shall provide a copy of the manufacturer’s Certificate of Analysis (COA) for the emulsified asphalt delivered to the project. If the asphalt emulsion is diluted at other than the manufacturer’s facility, the Contractor shall provide a supplemental COA from an independent laboratory verifying the asphalt emulsion properties.

The COA shall be provided to and approved by the RPR before the emulsified asphalt is applied.  The furnishing of the vendor’s certified test report for the asphalt material shall not be interpreted as a basis for final acceptance.  The manufacturer’s COA may be subject to verification by testing the material delivered for use on the project.

  1. Health, safety, and environment. The Contractor must provide a complete Safety Data Sheet (SDS) in accordance with U.S. Department of Labor, Occupational Safety and Health Administration (OSHA), Regulations (Standards – 29 CFR), 1910.1200 which establishes the requirement and minimum information for the MSDS for hazardous materials. The MSDS, Section II, shall include the Chemical Abstracts Service (CAS) registry numbers for all applicable hazardous ingredients in the coal tar emulsion product. The Contractor must provide the manufacturer’s certification that the product complies with the Code of Federal Regulation (CFR) Title 40 – Protection of Environment. The manufacturer’s certification shall address compliance for Air Programs, Part 59, National Volatile Organic Compound Emission Standards for Consumer and Commercial Products (for the airport location) and Water Programs, Part 116, Designation of Hazardous Substances.

630-2.2 Aggregate. The aggregate shall be washed dry silica sand or boiler slag free of dust, trash, clay, organic materials or other deleterious substances. The aggregate shall meet the gradation requirements below when tested in accordance with ASTM C136. The refined coal tar emulsion supplier must give written approval of the aggregate used in the mix design.

GRADATION OF AGGREGATES*

Sieve SizePercent Retained
MinimumMaximum
#20 or coarser(0.850 mm)02
#30(0.600 mm)012
#40(0.425 mm)260
#50(0.300 mm)560
#70(0.212 mm)560
#100(0.150 mm)530
#140(0.106 mm)010
#200(0.075 mm)02
Finer than #20000.3
* Table represents the maximum range of aggregate gradations.

630-2.3 Water. Water used in mixing or curing shall be from potable water sources and at least 50ºF (10ºC).  Other sources shall be tested in accordance with ASTM C1602 prior to use. The pH of the water shall conform to the requirements of the coal tar emulsion manufacturer.

630-2.4 Crack sealant. Crack sealant shall be certified for compatibility with the refined coal tar emulsion by the manufacturer of the refined coal tar emulsion, and approved by the RPR.

630-2.5 Oil spot primer. Oil spot primer shall be certified for compatibility with the refined coal tar emulsion by the manufacturer of the refined coal tar emulsion, and approved by the RPR.

630-2.6 Pavement primer. Pavement primer shall be certified for compatibility with the refined coal tar emulsion by the manufacturer of the refined coal tar emulsion, and approved by the RPR.

COMPOSITION AND APPLICATION

630-3.1 Composition. The refined coal tar emulsion seal coat is to consist of a mixture of refined coal tar emulsion, water and aggregate, and be proportioned as shown in the table below titled “Composition of Mixture Per 100 Gallons (379 Liters) of Refined Coal Tar Emulsion.”  The composition must have written approval of the coal tar emulsion manufacturer.

630-3.2 Quantities of materials per square yard (square meter). The Contractor shall submit the recommended formulation of water, emulsion, aggregate and application rate proposed for use to a testing laboratory together with sufficient materials to verify the formulation at least [      ] days prior to the start of operations. The mix design shall be within the range shown in the table below. No seal coat shall be produced for payment until a mix has been approved by the RPR. The formulation shall pass the fuel resistance test in accordance with ASTM D5727.

The mix formula for each mixture shall be in effect until modified in writing by the RPR.

Improper formulations of coal tar pitch emulsion seal produce coatings that crack prematurely or do not adhere properly to the pavement surface. A minimum of five (5) days is recommended for job mix approval.

TABLE 1. GRADATION OF AGGREGATES*

Sieve SizePercent Retained
MinimumMaximum
#20 or coarser(0.850 mm)02
#30(0.600 mm)012
#40(0.425 mm)260
#50(0.300 mm)560
#70(0.212 mm)560
#100(0.150 mm)530
#140(0.106 mm)010
#200(0.075 mm)002
Finer than #20000.3
* Table 1 represents the maximum range of aggregate gradations. In all cases the refined coal tar emulsion supplier is to give written approval of the aggregate used in the mix design.

The numbers shown in the table represent the maximum recommended range of values. In all cases, the refined coal tar emulsion supplier is to give written approval of specific composition numbers to be used in the mix design.

Some specifications covering this type of coating have allowed sand loadings in excess of 10 pounds per gallon (1.2 kg/L) of refined coal tar emulsion. These coatings have not performed well in the field due to poor fuel resistance and loss of adhesion and are not recommended.

Additional coats may be specified for greater durability.

630-3.3 Application rate. Application rates are not to exceed 0.17 gal/yd2/coat (0.77 liters/m2/coat), and at no time are total coats to exceed 0.51 gal/yd2 (2.3 liters/m2).

630-3.4 Control strip. Prior to full production, the Contractor shall prepare a quantity of mixture in the proportions shown in the approved mix design sufficient to place a control strip a minimum of 250 square yard (209 m2) at the rate specified in the job mix formula. The test area shall be designated by the RPR and will be located on a representative section of the pavement to be seal coated. Separate control strips by a minimum of 200 feet between sections. The actual application rate will be determined by the RPR during placement of the control strip and will depend on the condition of the pavement surface.

The control strip shall be used to verify the adequacy of the mix design and to determine the application rate. The same equipment and method of operations shall be used on the control strip as will be used on the remainder of the work.

If the control strip proves to be unsatisfactory, the necessary adjustments to the job mix formula, mix composition, application rate, placement operations, and equipment shall be made. Additional control strips shall be placed and evaluated, if required. Full production shall not begin without the RPR’s approval. Acceptable control strips shall be paid for in accordance with paragraph 630-7.1.

A qualified manufacturer’s representative shall be present in the field to assist the Contractor in applying control areas and/or control strips to determine the optimum application rate of both emulsion and sand.

The control strip affords the Contractor and the Engineer an opportunity to determine the quality of the mixture in place as well as the performance of the equipment.

The application rate depends on the surface texture.

If operational conditions preclude placement of a control strip on the pavement to be treated, it may be applied on a pavement with similar surface texture.

The only test required on the composite mix placed in the field is the viscosity test. The fuel resistance test may be specified; however, this test takes 96 hours to run.

CONSTRUCTION METHODS

630-4.1 Weather limitations. The seal coat shall not be applied when the surface is wet or when the humidity or impending weather conditions will not allow proper curing. The seal coat shall be applied only when the atmospheric or pavement temperature is 50°F (10°C) and rising and is expected to remain above 50°F (10°C) for 24 hours, unless otherwise directed by the RPR.

630-4.2 Equipment and tools. The Contractor shall furnish all equipment, tools, and machinery necessary for the performance of the work.

  1. Distributors. Distributors or spray units used for the spray application of the seal coat shall be self-propelled and capable of uniformly applying 0.12 to 0.55 gallons per square yard (0.54 to 2.5 liters per square meter) of material over the required width of application. Distributors shall be equipped with removable manhole covers, tachometers, pressure gauges, and volume-measuring devices.

The mix tank shall have a mechanically powered, full-sweep, mixer with sufficient power to move and homogeneously mix the entire contents of the tank.

The distributor shall be equipped with a positive placement pump so that a constant pressure can be maintained on the mixture to the spray nozzles.

  1. Mixing equipment. The mixing machine shall have a continuous flow mixing unit capable of accurately delivering a predetermined proportion of aggregate, water, and emulsion, and of discharging the thoroughly mixed product on a continuous basis. The mixing unit shall be capable of thoroughly blending all ingredients together and discharging the material to the spreader box without segregation.
  2. Spreading equipment. Spreading equipment shall be a mechanical-type squeegee distributor attached to the mixing machine, equipped with flexible material in contact with the surface to prevent loss of slurry from the spreader box. It shall be maintained to prevent loss of slurry on varying grades and adjusted to assure uniform spread. There shall be a lateral control device and a flexible strike-off capable of being adjusted to lay the slurry at the specified rate of application. The spreader box shall have an adjustable width. The box shall be kept clean; coal tar emulsion and aggregate build-up on the box shall not be permitted.
  3. Hand squeegee or brush application. The use of hand spreading application shall be restricted to places not accessible to the mechanized equipment or to accommodate neat trim work at curbs, etc. Material that is applied by hand shall meet the same standards as that applied by machine.
  4. Calibration. The Contractor shall furnish all equipment, materials and labor necessary to calibrate the equipment. It shall be calibrated to assure that it will produce and apply a mix that conforms to the job mix formula. Commercial equipment should be provided with a method of calibration by the manufacturer. All calibrations shall be made with the approved job materials prior to applying the seal coat to the pavement. A copy of the calibration test results shall be furnished to the RPR.

630-4.3 Preparation of asphalt pavement surfaces. Clean pavement surface immediately prior to placing the seal coat by sweeping, flushing well with water leaving no standing water, or a combination of both, so that it is free of dust, dirt, grease, vegetation, oil or any type of objectionable surface film.  Remove oil or grease that has not penetrated the asphalt pavement by scraping or by scrubbing with a detergent, then wash thoroughly with clean water. After cleaning, treat these areas with the oil spot primer.  Any additional surface preparation, such as crack repair, shall be in accordance with Item P-101, paragraph 101-3.6.

630-4.4 Mixing. Blend the coal tar emulsion mixture in the equipment described in paragraph 630-4.2 using the ingredients described in paragraph 630-3.2. The mixing must produce a smooth homogeneous mixture of uniform consistency. (Consult coal tar emulsion supplier for its recommended order of addition of the ingredients.) During the entire mixing and application process, no breaking, segregating or hardening of the emulsion, nor balling or lumping of the sand is to be permitted. Continue to agitate the seal coat mixture in the mixing tank at all times prior to and during application so that a consistent mix is available for application.

Small additional increments of water may be needed to provide a workable consistency, but in no case is the water content to exceed the specified amount.

630-4.5 Application of slurry seal surface treatment. The aggregate filled slurry seal surface treatment shall be applied at a uniform rate determined in paragraphs 630-3.2 and 630-3.3.

In order to provide maximum adhesion, the pavement shall be dampened with a fog spray of water if recommended by the supplier. No standing water shall remain on the surface.

If a prime coat is required, mix and apply the prime coat as specified in paragraph 630-3.2.

Apply the first coat uniformly to obtain the rate determined in paragraph 630-3.4.

Each coat shall be allowed to dry and cure initially before applying any subsequent coats. The initial drying shall allow evaporation of water of the applied mixture, resulting in the coating being able to sustain light foot traffic. The initial curing shall enable the mixture to withstand vehicle traffic without damage to the seal coat.

Apply the second coat in the same manner as outlined for the first coat.

Additional coats shall be applied over the entire surface as directed by the RPR.

The finished surface shall present a uniform texture.

The final coat shall be allowed to dry a minimum of eight hours in dry daylight conditions before opening to traffic, and initially cure enough to support vehicular traffic without damage to the seal coat.

Where marginal weather conditions exist during the eight-hour drying time, additional drying time shall be required. The length of time shall be as specified by the supplier. The surface shall be checked after the additional drying time for trafficability before opening the section to vehicle traffic.

Where striping is required, the striping paint used shall meet the requirements of Item P-620, shall be compatible with the seal coat and as recommended by the coal tar emulsion manufacturer.

QUALITY CONTROL

630-5.1 Contractor’s certification. The Contractor shall furnish the manufacturer’s certification that each consignment of emulsion shipped to the project meets the requirements of ASTM D5727, except that the water content shall not exceed 50%. The certification shall also indicate the solids and ash content of the emulsion and the date the tests were conducted. The certification shall be delivered to the RPR prior to the beginning of work. The manufacturer’s certification for the emulsion shall not be interpreted as a basis for final acceptance. Any certification received shall be subject to verification by testing samples received for project use.

The Contractor shall also furnish a certification demonstrating a minimum of three years’ experience in the application of coal tar emulsion seal coats.

630-5.2 Sampling. A minimum of one sample per day shall be tested for the properties in the table above titled “Composition of Mixture Per 100 Gallons (379 Liters) of Refined Coal Tar Emulsion.” A random sample of approximately one-quart of the composite mix will be obtained daily by the Contractor and stored in a glass container. The containers shall be sealed against contamination and retained in storage by the Owner for a period of six months. Samples shall be stored at room temperature and not be subjected to freezing temperatures.

A sample of undiluted coal tar emulsion shall be obtained from each consignment shipped to the job.

630-5.3 Records. The Contractor shall maintain an accurate record of each batch of materials used in the formulation of the seal coat and provide the documentation to the RPR daily.

METHOD OF MEASUREMENT

630-6.1 The refined coal tar emulsion shall be measured by the [   gallon (liter)   ] [   ton (kg)   ]. Only the actual quantity of undiluted refined coal tar emulsion will be measured for payment.

630-6.2 Aggregate shall be measured by the ton (kg) of dry aggregate.

BASIS OF PAYMENT

630-7.1 Payment shall be made at the contract unit price per [   gallon (liter)   ] [   ton (kg)   ] for the refined coal tar emulsion and at the contract price per ton (kg) for aggregate.

630-7.2 Payment shall be made at the contract unit price per ton (kg) for aggregate.

These prices shall be full compensation for furnishing all materials, preparing, mixing, and applying these materials, and for all labor, equipment, tools, and incidentals necessary to complete the item.

Payment will be made under:

Item P-630-7.1             Refined Coal Tar Emulsion for Slurry Coat – per [   gallon (liter)   ] [   ton (kg)   ]

Item P-630-7.2             Aggregate – per ton (kg) of dry aggregate

REFERENCES

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

ASTM International (ASTM)

ASTM C67                   Standard Test Method for Sampling and Testing Brick and Structural Clay Tile

ASTM C136                 Standard Test Method for Sieve or Screen Analysis of Fine and Coarse Aggregates

ASTM C1602               Standard Specification for Mixing Water Used in the Production of Hydraulic Cement Concrete

ASTM D490                Standard Specification for Road Tar

ASTM D3699              Standard Specification for Kerosine

ASTM D5727              Standard Specification for Emulsified Refined Coal Tar (Mineral Colloid Type)

Code of Federal Regulations (CFR)

29 CFR Part 1910.1200 Hazard Communication

40 CFR                         Protection of the Environment

END OF ITEM P-630