Section 4121. Granular Subbase Material
4121.01 DESCRIPTION.
Aggregate of the following types:
· Crushed stone,
· Gravels of which 30% or more of the particles retained on the 3/8 inch sieve have at least one fractured face as defined in Materials I.M. 305,
· Crushed PCC pavement meeting the requirements of Materials I.M. 210, or
· Uniformly blended combinations of these materials.
4121.02 GRADATION.
A. Crushed material: meet the requirements for Gradation No. 12a of the Aggregate Gradation Table, Article 4109.02.
B. Gravel: meet the requirements for Gradation No. 12b of the Aggregate Gradation Table, Article 4109.02.
4121.03 QUALITY.
The requirements of Table 4121.03-1 apply to the individual virgin aggregates before combining:
Table 4121.03-1: Coarse Aggregate Quality (Virgin Material)
|
Coarse Aggregate Quality |
Maximum Percent Allowed |
Test Method |
|---|---|---|
|
Abrasion |
50 |
AASHTO T 96 |
|
Alumina(a, b) |
1.5 |
Iowa DOT Materials Laboratory Test Method No. 222 |
|
A Freeze |
25 |
Iowa DOT Materials Laboratory Test Method No. 211, Method A |
(a) If the Alumina value passes, the A-Freeze is not needed for specification compliance.
If the Alumina value fails, determine the A Freeze value for specification compliance.
(b) Alumina does not apply to gravel.