ITEM 303 – BITUMINOUS SEAL COAT

303. 1 Description

This Item shall consist of an application of bituminous material with or without an application of aggregate on an existing bituminous surface course in accordance with the Plans and Specifications.

303.2 Material Requirements

Bituminous material shall be either Rapid Curing (RC) Cut-back or Emulsified Asphalt, whichever is called for in the Bill of Quantities. It shall conform to the requirements of Item 702, Bituminous Materials. The type and grade shall be specified in the Special Provisions.

303.2.1 Quantities of Materials

The approximate amounts of materials per square meter for seal coats of the several types shall be as provided in Table 303.1. The exact amounts to be used shall be set by the Engineer.

Table 303.1 – Quantities of Materials for Seal Coats

	Type 1	Type 2	Type 3
Bituminous material L/m2 Cover Aggregate, kg/ m2	0.20 – 0.50 None	0.51 – 1.00 5.00 – 10.00	1.01 – 1.50 10.01 – 14.00

303.2.2 Bituminous Materials

Bituminous material shall be Asphalt Cement, Penetration Grade 85 – 100, Rapid Curing (RC) Cut-back Asphalt. It shall conform to the requirements of Item 702, Bituminous Materials, whichever is called for in the Bill of Quantities. The type and grade of asphalt cement or cut-back asphalt will be specified in the Special Provisions.

303.2.3 Cover Aggregate

Cover Aggregate for Type 2 seal coat shall consist of sand and fine screenings, reasonable free from dirt or other organic matter.

Aggregate for type 3 seal coat shall be crushed stone, crushed slag or crushed gravel. Only one type of aggregate shall be used in a project unless alternative types are approved.

Aggregate gradation shall conform with Table 303.2 when tested by AASHTO T 27.

Table 303.2 – Grading Requirements

Sieve Designation		Mass percent Passing
Standard,mm	Alternate US Standard	Type 2	Type 3
			Grading A	Grading B
12.50 9.50 4.75 2.36 1.18 0.300 0.150	½ in. 3/8 in. No. 4 No. 8 No. 16 No. 50 No. 100	- 100 85 – 100 60 – 100 - - 0 - 10	- 100 85 – 100 10 – 40 0 – 10 0 – 5 -	100 85 – 100 10 – 30 0 – 10 0 – 5 - -

The aggregate shall have a mass percent of wear not exceeding 40 when tested by AASHTO T 96.

When crushed slag is used, it shall be uniform density and quality and shall have a density of not less than 960 kg/m3 as determined by AASHTO T 19.

303.3 Construction Requirements

303.3.1 Weather and Moisture Conditions

Seal coating shall not be undertaken during foggy or rainy weather or when the surface to be treated is wet. Wet cover coat material shall not be used on the work. No seal coating work shall be continued at night unless provided with sufficient lighting. The Engineer shall always be consulted before the commencement of the work and all work shall be terminated at once in the event of rain.

303.3.2 Preparation of Surface

Seal coating operations shall not be started until the bituminous surface is thoroughly compacted by traffic and rolling. In no event shall seal coat be placed on newly constructed or reconditioned surfaces in less than ten (10) days after such surface is laid and opened to traffic, unless ordered in writing by the Engineer.

Immediately prior to applying the bituminous material, the surface shall be cleaned of all dirt, sand, dust and other objectionable materials. This cleaning shall be effected by means of a rotary power broom or a power blower, unless other methods are authorized by the Engineer. Dried mud or other foreign materials which cannot be removed otherwise shall be removed by hand methods.

303.3.3 Application of Bituminous Material

Bituminous material shall be applied by means of a pressure distributor at the rate of approximately 0.9 to 1.8 liters for asphalt cement and 1.5 to 3.0 liters for cut-back asphalt per square meter of surface, in a uniform, unbroken spread over the section to be treated. The pressure distributor used for applying asphaltic materials shall be equipped with pneumatic tires and shall be designed and operated so as to distribute the asphaltic material at the specified rate. It shall be equipped with a fifth wheel tachometer registering the speed and so located as to be visible to the truck driver. The distributor pump shall be equipped with a gauge registering liters per minute passing through the nozzles and readily visible to the operator. Other suitable measuring devices approved by the Engineer may be used. The exact quantity to be applied shall be determined by the Engineer. The temperature at the time of application shall be within the range of temperature specified under Item 702, Bituminous Materials. Care shall be taken that the application of bituminous material at the junction of spreads is not in excess of the specified quantities. Any excess shall be removed from the surface by a squeegee. If necessary, to obtain proper junction of spreads, a strip of manila paper approximately 1 meter wide and at least as long as the spray bar shall be used at the beginning and end of each spread. The paper shall be removed after use.

Any skipped areas or recognized deficiencies shall be corrected immediately by hand application and hand operated pressure devices or by other equally suitable means.

In the event that nay structure becomes discolored with bituminous material, the Contractor, at this own expense, shall remove discoloration to the satisfaction of the Engineer.

303.3.4 Application of the Cover Aggregate

Immediately after the application of asphalt, the cover aggregate shall be evenly spread over the surface at the rate or approximately 0.004 to 0.007 cubic meter per square meter. The exact quantity shall be as directed by the Engineer. Spreading shall be accomplished by aggregate spreader only so that an even and accurate distribution is obtained. The used of spreader boards attached to tail gates of trucks shall not be permitted. The tires of the aggregate trucks shall at no time come in contact with the uncovered and newly applied asphalt.

As soon as the cover aggregate has been spread, the surface shall be broomed lightly with approved push or drag broom to insure an even distribution, and shall then be rolled with an approve power roller weighing not less than 5, nor more than 6 tonnes to a uniform surface.

303.3.5 Maintenance

The Contractor shall be responsible for the maintenance of the surface until the work is accepted by the Engineer. The maintenance work shall consist of keeping any excess aggregate evenly spread over the asphalt surface by approved sweeping devices. It shall also consist of keeping all potholes or failures which may occur, repaired by use of additional asphalt and necessary aggregate. All fat or bleeding surfaces shall be covered with approved cover aggregate so that the asphalt will not adhere to, or be picked up by the wheels of vehicles.

303.4 Method of Measurement

The quantities of bituminous material and cover aggregate shall be measured by the tonne (t), calculated by the actual rate of application approved by the Engineer.

303.5 Basis of Payment

The accepted quantities, measured as prescribed in Section 303.4, shall be paid for at the contract unit price for Bituminous Seal Coat, which price and payment shall be full compensation for furnishing and placing all materials, including all labor, equipment, tools and incidentals necessary to complete this Item.

Payment will be made under:

Pay  Item Number	Description	Unit of Measurement
303 303 (1) 303 (2) 303 (3) 303 (4)	Bituminous Seal Coat Cover Aggregate, Type ___ MC ___ Cut-back Asphalt RC ___ Cut-back Asphalt Asphalt Cement Pen. Gr.	Tonne Tonne Tonne Tonne