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

602.9.8.2. The brushed surface texture shall be applied evenly across the slab in one direction by
the use of a wire brush not less than 450 mm wide but longer brushes are preferred. The brush
shall be made of 32 gauge tape wires grouped together in tufts spaced at 10 mm centers. The
tufts shall contain an average of 14 wires and initially be 100 mm long. The brush shall have two
rows of tufts. The rows shall be 20 mm apart and the tufts in one row shall be opposite the centre
of the gap between tufts in the other row. The brush shall be replaced when the shortest tuft
wears down to 90 mm long.
602.9.8.3. The texture depth shall be determined by the Sand Patch Test as described in Clause
602, 12. This test shall be performed at least once for each day’s paving and wherever the
Engineer considers it necessary at times after construction as under:
Five individual measurements of the texture depth shall be taken at least 2 m apart anywhere
along a diagonal line across a lane width between points 50 m apart along the pavement. No
measurement shall be taken within 300 mm of the longitudinal edges of a concrete slab
constructed in one pass.
602.9.8.4. Texture depths shall not be less than the minimum required when measurements are
taken as given in Table 600-2 nor greater than a maximum average of 1.25 mm.
TABLE : 600-2. Texture Depth
Time of Test
1. Between 24 hours and 7 days after
the cons tn., of the slab or until
(he dab is first used by vehicles.)
2. Not later than 6 weeks before the
mad is opened to public traffic.
Number of
Measurements
An average of
5 measurements
An average of
5 measurements
Required Texture Depth (mm)
Specified
Tolerance
Value
1.00 ±0.25
1.00
±0.25
±0.35
602.9.8.5. After the application of the brushed texture, the surface of the slab shall have a uniform
appearance.
602.9.8.6. Where the texture depth requirements are found to be deficient, the Contractor shall
make good the texture across the full lane width over length directed by the Engineer, by
retexturing the hardened concrete surface in an approved manner.
602.9.9. Curing
602.9.9.1. Immediately after the surface texturing, the surface and sides of the slab shall be cured
by the application of approved resin- based aluminised reflective curing compound which hardens
into an impervious film or membrane with the help of a mechanical sprayer. Curing compounds
shall contain sufficient flake aluminium in finely divided dispersion to produce a complete overage
of the sprayed surface with a metallic finish. The compound shall become stable and impervious
to evaporation of water from the surface of the concrete within 60 minutes of application and shall
be of approved type. The curing compounds shall have a water retention efficiency index of 90
per cent in accordance with BS Specification No. 7542.
602.9.9.2. The curing compound shall not react chemically with the concrete and the film or
membrane shall not crack, peel or disintegrate within three weeks after application. Immediately
prior to use, the curing compound shall be thoroughly agitated in its containers. The rate of
spread shall be in accordance with the manufacturer’s instructions checked during the
construction of the trial length and subsequently whenever required by the Engineer. The