Section 4131.  Porous Backfill Material

                                                    

4131.01     DESCRIPTION.

Gravel or crushed stone.

 

4131.02     GRADATION.

Meet the requirements of Gradation No. 29 of the Aggregate Gradation Table, Article 4109.02.

 

4131.03     QUALITY.

No visible clay lumps, friable particles, and clay coatings. Meet the requirements of Table 4131.03-1:

 

Table 4131.03-1: Aggregate Quality (Porous Backfill Material)

Aggregate Quality

Maximum Percent Allowed

Test Method

Abrasion

50

AASHTO T 96

Alumina(a, b)

0.7

Iowa DOT Materials Laboratory Test Method No. 222

A Freeze

10

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

Shale

5

Materials I.M. 345

(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.