Section 4123. Modified Subbase Material.

• Crushed stone,
• Gravels for which 75% 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.
• Recycled pavements meeting Materials I.M. 210, or
• Uniformly blended combinations of these materials with a maximum of 50% RAP.

4123.02 GRADATION.
Meet the requirements for Gradation No. 14 of the Aggregate Gradation Table, Article 4109.02.

Process RAP to pass the 2 inch (50 mm) sieve.

Uncrushed gravel and/or sand may be uniformly blended with crushed recycled pavement or crushed stone at a maximum rate of 50% to meet gradation requirements.

4123.03 QUALITY.
The following requirements apply to blended and non-blended virgin materials:

TABLE 4123.03
Aggregate Quality	Maximum Percent Allowed	Test Method
Abrasion	45	AASHTO T 96
C Freeze	15	Iowa DOT Materials Laboratory Test Method 211, Method C
Alumina (a)	0.7 (Abrasion loss 46% to 55%)	Iowa DOT Materials Laboratory Test Method 222
A Freeze	10 (Abrasion loss 46% to 55%)	Iowa DOT Materials Laboratory Test Method 211, Method A
Alumina (No. 40 (425 μm) material)	4.7	Iowa DOT Materials Laboratory Test Method 222
(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.

Acquire gravel or gravel/non-gravel blend products from a gravel source with a plasticity index not exceeding 7.