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

501.8. Preparation of Surface
501.8.1. General: This work shall consist of preparing an existing granular or black-topped
surface bituminous course. The work shall be performed on such widths and lengths as shown on
the approved drawings or as instructed by the Engineer in charge. The existing surface shall be
firm and clean, and treated with Prime or Tack coat as shown on the drawings as otherwise
stated in the Contract.
501.8.2. Materials
501.8.2.1. Scarifying the existing granular base course and re-laying the granular surface:
The material used shall be coarse aggregate saved from the scarification of the existing granular
base course supplemented by fresh coarse aggregate and screenings so that aggregates and
screenings thus supplemented correspond to Clause 404: Water Bound Macadam or Clause 406:
Wet Mix Macadam of the Ministry’s Specification for Road and Bridge Works (third revision) 1995.
501.8.2.2. For patching potholes sealing cracks: Where the existing surface to be overlaid is
bituminous, any existing potholes and cracks shall be repaired and sealed as stated below.
(1)The existing bituminous surface should be inspected and all potholes and patch areas made
free o any loose, defective material. The edges of all potholes shall be cut/trimmed with hand
tools vertically to form rectangular shape and shall be thoroughly cleaned with wire brush,
compressed air or other approved means, all dust and loose materials should be removed from
site. Layers below the level of bituminous construction should be replaced using material of
equivalent specification to the original construction and degree of compaction. The area of
bituminous construction should be primed and / or tacked with an emulsion (meeting requirement
of IS: 8887) depending on whether the lower area is granular or bituminous in nature. The sides
of the excavated position should be painted with tack coat material using a hand brush/sprayer.
(2)The bituminous patching material should be either a hot mix or a cold mix, adopting the
reactive specification. The bituminous mixture, prepared in a plant of suitable capacity should be
placed in layers of not more than 100 mm (loose) and compacted in layers with roller/plate
compactor/ hand roller/ rammer to the desired compaction standard.
(3) In the final layer the mix should be spread slightly proud of the surface so that after rolling, the
surface shall be flush with the adjointing surface.
(4) Where required, a seal coat should be applied as per the specified procedure. the surface
levels should be checked using a 3m straight edge.
Crack sealing:-
(1) The fine cracks (less than 3 mm in width) should be sealed by for spray, which is a very light
application of low viscosity slow setting emulsion. Prior to this treatment it is important that the
surface is thoroughly cleaned, preferably with compressed air. The fog spray should be applied at
a rate of 0.5-1.0 liter/m 2 of the specified emulsion. Using 0.5 -1.0 liter /m 2 of the specified
emulsion, using an approved hand held sprayer.
(2)The wide cracks (more than 3 mm in width) should be filled with crusher dust or other
approved fine material passing 4.75 mm sieve to a level about 5 mm below the road surface
level. After sweeping the surface clear of dust slow setting emulsion should be poured in the
cracks, minimizing any spillage. If spillage does occur, crusher dust should be applied to bolt up
the spillage. Isolated areas, with wide cracks, shall be cut and patched.
501.8.2.3. For profile corrective course: A profile corrective course for correcting the existing
pavement profile shall be laid to varying thickness as shown on the approved drawings. The
profile corrective course shall be laid to tolerances and densities as specified for wearing course if
a single layer, or base course, if it is to be covered with a wearing course layer.