Specification Part 3 - Road & Bridge Works - Urban Administration ...

The equipment and general procedure shall all be in accordance with the Manual for Construction
and Supervision of Bituminous Works. For relatively small areas of surface dressing, careful
application of chips by hand may be acceptable if approved by the Engineer. The rate of
application of chips shall be as determined by the procedure given in the Manual for Construction
and Supervision of Bituminous Works. Immediately after application of the binder, clean, dry
chips (in the case of emulsion binder the chippings may be damp) shall be spread uniformly on
the surface so as to cover the surface completely with a single layer of chips.
It is desirable that clean, dry chippings be used, properly screened. Best results are obtained
when as little time as possible elapses between the application of a hot binder and chippings and
in no case should this interval exceeds 15 minutes. The chippings should be uniformly distributed
and precautions taken that the whole of the sprayed surface is covered uniformly without any
accumulation of surplus material at any point. The chippings should be spread with a circular
sweep of the shovel. Where different sizes of chips are to be used, spread the large size first and
then the fines this will give a smoother finish. If road is rutted the bigger chips may be used in the
ruts and smaller chips on the remainder. Hand brooming or light drag brooming should follow the
application of the chippings prior to rolling. The excess of the chippings should be removed not
less then 48 hours after applications and should not be swept back on the road. The chippings
should not be dumped on the road, and should be cast parallel to the axis of the road and not
across it.
TABLE 500-22.
SPRAYING TEMPERATURES FOR BINDERS
Binder grades Whirling
Slot jets
spray jets
Min°C Max°C Min°C Max°C
Penetration Grades
400/500 160 170 140 150
280/320 165 175 150 160
180/200 170 190 155 165
80/100 180 200 165 175
510.3.5. Rolling:
(i)Rolling of the chips should preferably be carried out by a pneumatic tyred roller in accordance
with Clause 501.6 and Clause 501.7.
(ii)Traditional steel wheeled rollers tend to crush the aggregates and if their use cannot be
avoided their weight should be limited to 8 tonnes.
(iii)Rolling shall commence at the edges and progress towards the centre except in super
elevated and uni-directional cambered portions where it shall proceed from the lower edge to the
higher edge.
(iv)Each pass of the roller shall uniformly overlap not less than one-third of the track made in the
preceding pass.
(v)While rolling is in progress additional chips shall be spread by hand in necessary quantities
required to make up irregularities.
(vi)Rolling shall continue until all aggregate particles are firmly embedded in the binder and
present a uniform closed surface.
510.3.6. Application of second coat of surface dressing: Where surface dressing in two coats
is specified, the second coat should not be applied until the first coat has been open to traffic for 2
or 3 weeks. The surface on which the second coat is laid must be clean and free of dust. The
construction operations for the second coat shall be the same as described in Clauses 510.3 .3 to
510.3.5.
510.4. Opening to Traffic
(i)Traffic shall not be permitted to run on any newly surface dressed area until the following day.
510.5. Surface Finish and Quality Control of Work