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

(i)It is usual to use ordinary Portland cement, hydrated lime or other additives to control
consistency, mix segregation and setting rate.
(ii)The proportion of the additive should not normally exceed 2 percent by weight of dry
aggregates.
516.3. Mixture Design
(i)A range of residual binder contents for each aggregate grading is given in Table 500-33.
(ii)The optimum mixture design for the aggregate, additive, water and bitumen emulsion mixture
should be determined in accordance with ASTM D 3910.
516.4. Construction Operations
516.4.1. Weather and seasonal limitations: Clause 501.5.1 shall apply.
TABLE 500-33.
AGGREGATE GRADING, BINDER CONTENT AND APPROXIMATE COVERAGE RATE
Percentage by mass pissing
finished thickness of sealing
5mm 3mm 1. 5mm
9.5 100 - --
4.75 90 - 100 100 —
3.35 - 80- 100 100
236 65 - 90 75-100 95-100
1.18 45 - 70 55 -90 70-95
0.600 30 - 50 35 -70 55-75
0.300 18- 30 20- 45 30- 50
0.150 10-21 10-25 10-30
0.075 5- 15 5- 15 5-15
Sieve Size (mm)
Quantity of residual
binder
percentage by mass
of aggregate
Approximate
coverage rate
(kg/m 2)
7.5- 13.5 10- 16 12-20
8 -15 4-6 2-4
516.4.2. Surface preparation:
(i)Any necessary remedial work to the road surface and structure shall be completed either prior
to or as part of the Contract or agreed as acceptable by the Engineer in charge, according to the
provisions of Clause 501.
(ii)Before slurry seal is applied, street furniture and, where directed by the Engineer in charge,
road markings, shall be masked using self-adhesive masking material or other material firmly
secured against the passage of the spreader box or the tools used for hand laying.
(iii)Any packed mud or other deposits on the surface shall be removed, all organic growth shall be
removed by suitable means, and the surface shall be swept free of all loose material.
516.4.3. Tack coat:
(i)If required by the Engineer in charge, a tack coat may be applied prior to the slurry seal, with or
without grit or chips, in order to seal the existing substrata and enhance the bond to the existing
road surface.
(ii)Unless otherwise agreed by the Engineer in charge, the rate of spread of tack coat shall be
0.15 to 0.30 litres/m2 for bituminous surfaces and 0.4 to 0.6 litres/m2 for concrete surfaces
516.4.4. Mixing and transportation of mixture:
(i)Mixing (and laying) techniques vary according to the type of emulsion used.