PREPARATION OF THE EXISTING ROAD SURFACE FOR DRESSING
It is very essential to examine the water –bound macadam
carefully before deciding to surface dress it. (See Patching of Potholes under
preparation of base for Laying Bituminous Courses.) If the existing surface shows
any depressions, potholes, ruts or irregularities exceeding 12mm or has a
steeper camber than 1 in 60, it must be re-conditioned. If the surface is not
so bad as to warrant resectioning it should be patch repaired a week or two
before the surface dressing is to be started, and left open to traffic. Stone
metal of the old untreated road surface should be exposed to a depth of 6mm to
12mm to give the binder a better opportunity of penetrating and binding the
road. Care should, however, be taken to see that the stability of the road is
not disturbed and the stone metal is not loosened.
It is most important that the surface of the road shall be thoroughly
cleaned before the application of a binder. It shall be swept clean and free
from dust , dirt, caked earth and any other
extraneous matter. The cleaning shall be done first with hard wire brushes,
then with softer brushes or base brooms and finally by fanning or blowing with
gunny bags or sacks to remove all lose dust. The road must be absolutely dry
before painting is commenced and this dry condition must extend right down to
the earth subgrade or for at least 6cm incase of emergency.
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