First of all i want to tell you that DBM act as bituminous base course while BC acts as wearing course.
LAYING OF DBM(Dense Bituminous macadam) /BC(Bituminous concrete)
Laying of DBM/BC is done with the help of paver. There are following points which clearly indicates detailed process of laying.
To know more about the bituminous concrete (BC) ,please click on below link.........
1-Weather and seasonal limitations-
Laying shall be suspended:
A- In presence of standing water on the surface
B-When rain is imminent, and during rain, fog, or dust storm
C-When the base/binder course is damp
D-When the air temperature on the surface
on which it is to be laid is less than 10°C for mixes with conventional bitumen and is less than 15°C for mixes with modified bitumen
E- When the wind speed at any temperature exceed the 40 km per hour at 2 m height.
2-Cleaning of surface-The surface on which the bituminous work is to be laid shall be cleaned of all loose and extraneous matter by means of a mechanical broom and air jet. The equipment for applying a high pressure air jet from a compressor to remove dust or loose matter shall be available full time at the site.
3-Spreading – prior to spreading the mix, the base shall be well prepared. Except the area where paver cannot get access, bituminous materials shall be spread, levelled and tamped by an approved self-propelled paving machine equipped with an electronic sensing device.
When laying binder course or wearing course approaching an expansion joint of a structure, machine laying shall stop 300 mm short of the joint. The remainder of the pavement up to the joint, and corresponding area beyond, it shall be laid by hand, and the joint or joint cavity shall be kept clear of surfacing material.
To know more about the Dense Bituminous macadam (DBM) ,please click on below link.........
4- Cleanliness and Overlaying-Bituminous material shall be kept clean and uncontaminated.
Binder course material shall be covered by either the wearing course or surface treatment whichever is specified in the contract.
5-Compaction-Bituminous material shall be laid and compacted in layers, Which enable the specified thickness, surface level, regularity requirements and compaction to be achieved. Compaction of bituminous materials shall commence as soon as possible after laying and completed before the temperature falls below min. Rolling temperature. Rolling shall commence at the edges and progress towards center longitudinally except that on super elevation and unidirectionally cambered portions, it shall progress from lower to the upper edge parallel to the C.L. of the pavement. Rolling shall be continued until all roller marks have been removed from the surface. The initiator breakdown rolling shall be done with 8-10 tonne static weight smooth- wheel rollers. The intermediate rolling shall be done with 8-10 tonne static weight or vibratory roller or with a pneumatic tyre roller (PTR) of 12 to 15 tonne weight, with a tyre pressure of at least 0.56 MPa. The finish rolling shall be done with 6 to 8 tonne smooth wheel tandem rollers.
The roller shall first compact material adjacent to joints and then work from the lower to the upper side of the layer, overlapping on successive passes by at least one-third of the width of the rear roll or, in the case of pneumatic tyres roller at least the nominal width of 300 mm.
Quantity / Compaction Factor value / Loose thickness calculation for DBM/BC(Bituminious layer)
In portions with super- elevated and unidirectional camber, after the edge has been rolled, the roller shall progress from the lower to the upper edge.
Roller should move at least at a speed of not more than 5 Km per hour.
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Thanks a lot