MANUAL 4 - Construction Industry Development Board

MANUAL 4 – BITUMINOUS PAVEMENT SEALS
Figure 4.12
Therefore, if the quantity of emulsion to be used in the mix is 290 litres/m³, this amount of
emulsion must be reduced by a factor of x/y i.e. x/y times 290.
The amount of emulsion to be used per m³ is therefore:
290 – ( x/y ) 3 290 = 290 (1– x/y ) litres.
Note
Using uniformly damp aggregate reduces the amount of water to be added to the
mixture to produce the slurry. It also overcomes the problem of balling of the fines when
emulsion is added.
If the aggregate to be used is completely dry it is recommended that a small amount of
water be added to the aggregate in the mixture after adding the cement to ensure no
balling of the mix takes place when the emulsion is added.
5.2 Addition of cement
It is essential to add cement to any slurry for the following reasons:
1. It eliminates the segregation of the diluted emulsion from the coarse aggregate and
the emulsion floating to the surface of the spread slurry. It also increases the adhesion
of binder to aggregate.
2. It acts as a catalyst in the mixed slurry, inducing the emulsion to break by absorbing
water from the emulsion.
3. It improves the workability of the slurry, giving it the creamy texture, assisting the
coating of the fine and coarse aggregate and keeping it in suspension.
4. It also improves the grading of the aggregate on the finer side of the grading curve.
Normally ± 1% of aggregate by mass of cement is added to the mix, but this can be increased
to 2% if there is a shortage of fines.
IMPLEMENTING EMPLOYMENT INTENSIVE ROAD WORKS 51
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