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Sustainable Drainage Systems
Stormwater Drainage
Sub-base course Aggregate
Aggregates should comply with BS EN 13242 : 2002, Aggregates for unbound and hydraulically bound materials for use in civil engineering work and road construction. Table1. below shows typical grading for sub-base materials. The grading of material for use in the sub-base of a permeable pavement is a compromise between stiffness, for stability, and void space for water storage and therefore conventional Type 1 sub-base materials are not suitable. The table is also available for download from this site.
Table 2 )
Sieve size (mm) |
Percentage |
Passing |
|
Main Drainage layer |
Transfer layer |
63 |
98-100 |
- |
40 |
85 - 99 |
100 |
31.5 |
- |
98-100 |
20 |
20 - 70 |
85 - 99 |
10 |
- |
20 - 70 |
4 |
0 - 15 |
0 - 15 |
2 |
0 - 5 |
0 - 5 |
As the aggregate has a low fines content, the load carrying capabilities within the aggregate, is achieved by point to point contact between aggregate particles. It is therefore necessary that the aggregate be of an angular nature to maximize the frictional contact between aggregate particles. Sands and gravels with rounded particles are not suitable for this type of construction.
A test for aggregate durability is also required to ensure that the aggregate will not degrade due to being in contact with water for long periods of time.
Specification for open graded sub-base for use as storage below pervious pavements.
This table is also available as a word document download.
| Properties | Category to BS EN 13242 or BS 12620 | ||||||||||||||||||||||||||||||||||||
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