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.