Granular material used for drainable subbase shall conform to IDOT Specification 4121 and 4109 for gradation 12a. If access or construction sequencing requires that concrete trucks must drive on the drainable subbase course to place the fresh concrete, gradation 14 may be used with the approval of the engineer. Recycled concrete may not be used.
Standard Sieve Size
|
1 1/2”
|
1”
|
3/4”
|
1/2”
|
3/8”
|
4
|
8
|
30
|
50
|
100
|
200
|
Granular subbase | 100 | 40—80 | 5—25 | 0—6 | |||||||
Modified Subbase | 100 | 70—90 | 10—40 | 3—10 |