ITEM 301 – BITUMINOUS PRIME COAT

301. 1 Description

This Item shall consist of preparing and treating an aggregate base course with material in accordance with the Plans and Specifications, preparatory to the construction of a bituminous surface course.

301.2 Material Requirements

Bituminous material shall be either Rapid Curing (RC) or Medium Curing (MC) Cut-back 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.

301.3 Construction Requirements

301.3.1 Surface Condition

Prime coat shall be applied only to surfaces which are dry or slightly moist. No prime coat shall be applied when the weather is foggy or rainy.

301.3.2 Equipment

The liquid bituminous material shall be sprayed by means of a pressure distributor of not less than 1000 liters capacity, mounted on pneumatic tires of such width and number that the load produced on the road surface will not exceed 1kN(100 kgf) per cm width of tire.

The tank shall have a heating device able to head a complete charge of bituminous liquid to 1800C. The heating device shall be such that overheating will not occur. Consequently, the flames must no directly touch the casing of the tank containing the bituminous liquid. The liquid shall be insulated in such a way that the drop in temperature when the tank is filled with bituminous liquid at 1800C and not heated will be less than 20C per hour. A thermometer shall be fixed to the tank in order to be able to measure continuously the temperature of the liquid. The thermometer shall be placed in such a way that the highest temperature in tank is measured. The tank shall be furnished with a calibrated dipstick to indicate the contents. The pipes for filling the tank shall be furnished with an easily changeable filter.

The distributor shall be able to vary the spray width of the bituminous liquid in maximum steps of 100 mm to a total width of 4 m. The spraying bar shall have nozzles from which the liquid is sprayed fan-shaped on the road surface equally distributed over the total spraying width.

For application of the liquid bituminous material, the distributor shall have a pump either driven by a separate motor, or with a device to synchronize its speed with the speed of the distributor. The pump shall be furnished with an indicator showing the rate of flow. The suction side of the pump shall have an easily changeable filter. A thermometer shall be fixed, such that it indicates the temperature of the liquid immediately before it leaves the spraying bar.

The distributor shall be furnished with a tachometer, indicating its forward speed, which shall be visible from the driver’s seat. The distributor shall be designed so that the deviation from the prescribed rate of application does not exceed 10% and shall be equipped with a device for hand spraying of the bituminous liquid.

301.3.3 Application of Bituminous Material

Immediately before applying the prime coat, the full width of surface to be treated shall be ensured to be free from all dirt and other objectionable materials. When required by the Engineer, immediately prior to the application of the prime coat, the surface shall be slightly sprayed with water but not saturated. Bituminous material shall be applied by means of a pressure distributor at the temperature given in Item 702, Bituminous Materials. The rate of application of the bituminous material shall be within the range of 1 to 2 liters/m2. The exact application rate for the type of the bituminous material to be ordered by the Engineer shall be based on the quantity of the base materials and field condition.

The prime coat shall be left undisturbed for a period of at least 24 hours or until such time that it has sufficiently cured as determined by the Engineer, and shall not be opened to traffic so that it will not be picked up by the wheels of passing vehicles. The Contractor shall maintain the prime coat until the next course is applied. Care shall be taken that the application of the bituminous material is not in excess of the specified amount. Any excess shall be blotted with sand or removed as directed by the Engineer. All areas inaccessible to the distributor shall be sprayed manually using the device for hand spraying. The surface of structures and trees adjacent to the areas being treated shall be protected in such a manner as to prevent their being spattered or marred.

301.4 Method of Measurement

Bituminous Prime Coat shall be measured by the area covered in square meters (m²).

301.5 Basis of Payment

The accepted quantity, measured as prescribed in Section 301.4, shall be paid for at the contract unit price for Bituminous Prime 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
301 301 (1) 301 (2)	Bituminous Prime Coat MC – Cut-back Asphalt RC - Cut-back Asphalt	Square Meters Square Meters