MANUAL 4 - Construction Industry Development Board

MANUAL 4 – BITUMINOUS PAVEMENT SEALS
Minimum temperature
°C
0
15
20
25
6.5 Design of slurry
6.5.1 Slurry seal binder content
Spraying temperature
°C
50
50
50
50
Table 4.7: Heating times for binder
Approximate time to heat
210 litre drum (min)
30 – 40
20 – 30
20 – 25
15 – 20
The slurry seal binder must be a stable grade 60% Anionic emulsion. The bulking of the
aggregate must be taken into consideration when determining the amount of emulsion
required for the mix.
Table 4.8 gives an indication of the slurry seal binder content for a range of traffic volumes
per m 3 of dry aggregate.
Traffic volume (vpd) Binder content (litres/m 3 )
50 – 500
500 – 1 500
1 500 – 2 500
6.5.2 Water content of slurry
Table 4.8: Binder content
60
240
230
The approximate amount of water to be added to the slurry is 235 litres per m 3 .
This amount could either be increased if the aggregate is completely dry and hot conditions
prevail, or reduced if the aggregate is damp.
It is recommended that a trial mix be prepared and, once the amount of water required is
established, it is used consistently for the rest of the work to obtain a uniform mix.
6.5.3 Aggregate for the slurry
Grading of aggregate
The aggregate for the Cape seal slurry must be carefully selected. Generally speaking,
the medium grade grading for the slurry must be selected. The grading curve depicted in
Table 4.9 can be used as a guide for selecting the aggregate.
Sieve size (mm) Percentage by mass passing
6,700
4,750
2,360
1,180
0,600
0,300
0,150
0,075
Table 4.9: Grading of aggregate
100
82 – 100
56 – 95
37 – 75
22 – 50
15 – 37
7 – 20
4 – 12
IMPLEMENTING EMPLOYMENT INTENSIVE ROAD WORKS 71
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