Scope :
This work shall consist of the application of a single coat of low viscosity liquid bituminous material to a porous granular surface preparatory to the superimposition of bituminous treatment or mix. The work shall be carried out on a previously prepared granular/ stabilized surface to Clause
Material :
The primer shall be cationic bitumen emulsion SS1 grade conforming to IS:8887 or medium curing cutback bitumen conforming to IS:217 or as specified in the Contract.
Quantity of SS1 grade bitumen emulsion for various types of granular surface and Cutback for primer shall not be prepared at the site. Type and quantity of cutback bitumen for various types of granular surface shall be as given in Table.
| Emulsion Bitumen
|
Cutback Bitumen
|
| Types of Surface |
Rate of Spray
(kg/sq.m) |
Types of Surface |
Cutback |
Rate of Spray
(kg/sq.m) |
| WMM / WBM |
0.7 – 1.0 |
WMM / WBM |
MC 30 |
0.6 – 0.9 |
| Stabilized soil bases/Crusher Run Macadam |
0.9 – 1.2 |
Stabilized soil bases/Crusher Run Macadam |
MC 70 |
0.9 – 1.2 |
The correct quantity of primer shall be decided by the Engineer and shall be such that it can be absorbed by the surface without causing run-off of excessive primer and to achieve desired penetration of about 8-10 mm.
weather and Seasonal Limitations :
Primer shall not be applied during a dust storm or when the weather is foggy, rainy or windy
or when the temperature in the shade is less than 100C. Cutback bitumen as primer shall not
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167
be applied to a wet surface. Surfaces which are to receive emulsion primer should be damp,
but no free or standing water shall be present. Surface can be just wet by very light sprinkling
of water.
Construction Equipment :
The primer shall be applied by a self-propelled or towed bitumen pressure sprayer equipped
for spraying the material uniformly at specified rates and temperatures. Hand spraying shall
not be allowed except in small areas, inaccessible to the distributor, or in narrow strips where
primer shall be sprayed with a pressure hand sprayer, or as directed by the Engineer.
502.4.2 P reparation of R oad Surface
The granular surface to be primed shall be swept clean by power brooms or mechanical
sweepers and made free from dust. All loose material and other foreign material shall
be removed completely. If soil/ moorum binder has been used in the WBM surface, part
of this should be brushed and removed to a depth of about 2 mm so as to achieve good
penetration.
Application of Bituminous Primer :
After preparation of the road surface as per Clause 502.4.2, the primer shall be sprayed
uniformly at the specified rate. The method for application of the primer will depend on the
type of equipment to be used, size of nozzles, pressure at the spray bar and speed of forward
movement. The Contractor shall demonstrate at a spraying trial, that the equipment and
method to be used is capable of producing a uniform spray, within the tolerances specified
No heating or dilution of SS1 bitumen emulsion and shall be permitted at site. Temperature of
cutback bitumen shall be high enough to permit the primer to be sprayed effectively though
the jets of the spray and to cover the surface uniformly.
Curing of Primer and Opening to Traffi
A primed surface shall be allowed to cure for at least 24 hours or such other higher period as is
found to be necessary to allow all the moisture/volatiles to evaporate before any subsequent
surface treatment or mix is laid. Any unabsorbed primer shall first be blotted with a light
application of sand, using the minimum quantity possible. A primed surface shall not be
opened to traffic other than that necessary to lay the next course.
Quality Control of Work :
For control of the quality of materials and the works carried out, the relevant provisions of
Section 900 shall apply.
Section 500 Bases and Surface Courses (Bituminous)
168
Arrangements for Traffic :
During construction operations, arrangements for traffic shall be made in accordance with
the provisions of Clause 112.
502.7 Measurement for Payment
Prime coat shall be measured in terms of surface area of application in square metres.
Rate :
The contract unit rate for prime coat shall be payment in full for carrying out the required
operations including full compensation for all components listed
and as applicable to the work specified in these Specifications. Payment shall be made on
the basis of the provision of prime coat at an application rate of quantity at 0.6 kg per square
metre or at the rate specified in the Contract, with adjustment, plus or minus, for the variation
between this quantity and the actual quantity approved by the Engineer..