MANUAL 4 - Construction Industry Development Board

MANUAL 4 – BITUMINOUS PAVEMENT SEALS
The area that one heap of 0,105 m 3 must cover is:
The volume of the heap in m3 , divided by the rate of application required in m3 /m2 , will give
the area that one measured heap will cover in m2 .
i.e. 0,105 m 3 = 12,65 m 2
0,0083 m 3 /m 2
If the width of the road is 3,5 m, then the length can be obtained by dividing the area by the
width, i.e.
Area = Length
Width
i.e.
12,65 m2 = 3,6 m
3,5 m
This is the distance between the spotted heaps of aggregate.
5.2.2 Application of binder for the seal
Types of binder
Emulsions are ideal for manual application, as they do not have to be heated to temperatures
of 130°C – 140°C, as is the case for penetration bitumen.
As they contain 35 – 40% water, the problem of over application, resulting in bleeding of the
surface, is overcome to a large extent.
The following binders can be used for seal work:
• Anionic spray-grade emulsion (60% bitumen and 40% water).
The viscosity of this binder is lower than the viscosity of a cationic emulsion, and the
rate of application for a tack coat reduces to approximately 0,7 to 0,8 litres per m 2
before the binder tends to flow, even when minimum gradients pertain.
Generally they do not require heating, unless the air temperature at the time of
spraying is below 20 – 25°C.
• Cationic spray-grade emulsion (65% bitumen and 35% water).
This emulsion is ideal for seal work. In cool weather it is advisable to heat the emulsion
with a low flame to 50°C.
Note
The flow properties of this emulsion are better than Anionic emulsions.
It is essential when using Cationic emulsion for the equipment to be thoroughly cleaned
out of any Anionic emulsion. The equipment must be flushed out with water and paraffin.
When heating Cationic emulsion, care must be taken to heat it with burners on a low
flame. The temperature to which it is heated must not exceed 50°C.
IMPLEMENTING EMPLOYMENT INTENSIVE ROAD WORKS 35
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