Section 4123. Modified Subbase Material



Aggregate of the following Types:

         Crushed stone,

         Gravels for which 75% 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,

         Recycled pavements meeting Materials I.M. 210, or

         Uniformly blended combinations of these materials with a maximum of 50% RAP.

         Do not place RAP below high water table.


4123.02 GRADATION.


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


B. Process RAP to pass the 2 inch sieve.


C. 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.


A. The requirements of Table 4123.03-1 apply to virgin materials:


Table 4123.03-1: Aggregate Quality

Aggregate Quality

Maximum Percent Allowed

Test Method




C Freeze


Iowa DOT Materials Laboratory Test Method No. 211, Method C


B. The requirements of Table 4123.03-1 apply to recycled PCC when the aggregate source is unknown as outlined in Materials I.M. 210.