MANUAL 4 - Construction Industry Development Board

MANUAL 4 – BITUMINOUS PAVEMENT SEALS
• When spacing the stone as above, the quantity required is reduced – the amount
of aggregate poured into the cylinder will be less resulting in a lower ALD reading,
resulting in lower stone application. This will mean the spotting distance between
each 105 litre spot will be further apart. By calculating the distance for spotting the
aggregate, this automatically controls the rate of application and the spacing of the
aggregate particles.
• If no pan and cylinder is available, 200 pieces of aggregate must be measured with
callipers and the average ALD determined. This ALD must be reduced by 10 – 15%
and the spotting distances calculated accordingly.
Example where ALD is determined using callipers
Assuming the Average Least Dimension (200 stones) of the aggregate measured with
callipers = 8,3 mm.
This must be reduced by 10% or 15% for Cape seal:
8,3 3 0,90 OR 8,3 3 0,85
= 7,47 mm OR = 7,055 mm
The rate of application of aggregate in m 3 /m 2 is obtained by dividing the above figures by
1 000:
0,00747 m 3 /m² OR 0,007055 m 3 /m²
Allowing for a 5% for wastage the rate of application = 0,00747 3 1,05 = 0,0078435
m 3 /m²
Calculation of spotting distance for 15% reduction
Width of road 2 3 3,5 m and measuring container = half a 210 litre drum = 0,105 m 3
(1 000 litres = 1 m 3 )
Number of m² that can be covered with 0,105 m 3
= 0,105 m 3 = 13,39 m²
0,0078435 m 3 /m²
For a width of 3,5 m this amount will cover a length of 3,39/3,5 = 3,8 metres.
So 105 litres (half 210 litre drum) are spotted/placed every 3,8 m.
IMPLEMENTING EMPLOYMENT INTENSIVE ROAD WORKS 67
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