4121 Granular Subbase Material

Section 4121. Granular Subbase Material.

4121.01 DESCRIPTION.

Crushed stone,
Gravels of which 30% or more of the particles retained on the 3/8 inch (9.5 mm) 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 following requirements apply to the individual virgin aggregates before combining:

TABLE 4121.03

Coarse Aggregate Quality Maximum Percent Allowed Test Method

Abrasion 50 AASHTO T 96

Alumina ^(a) 1.5 Iowa DOT Materials Laboratory Test Method 222

A Freeze 25 Iowa DOT Materials Test Laboratory Test Method 211, Method A

^(a) If the Alumina value fails, the A Freeze value shall be determined for specification compliance. Iowa DOT Materials Laboratory Test Method 222 does not apply to gravel.

TABLE 4121.03
Coarse Aggregate Quality	Maximum Percent Allowed	Test Method
Abrasion	50	AASHTO T 96
Alumina ^(a)	1.5	Iowa DOT Materials Laboratory Test Method 222
A Freeze	25	Iowa DOT Materials Test Laboratory Test Method 211, Method A
^(a) If the Alumina value fails, the A Freeze value shall be determined for specification compliance. Iowa DOT Materials Laboratory Test Method 222 does not apply to gravel.