Section 4120 _ Revised 10_21_2025.pdf
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- Solicitation number
- 645-RFB-2407-2026
- Issued by
- Johnson County, Iowa
About this file
This is a technical specification document issued by the Iowa Department of Transportation (Iowa DOT) defining material requirements for granular surfacing and shoulder aggregate used in state highway construction and maintenance projects. Section 4120 establishes comprehensive standards for crushed stone, gravel, and recycled material mixtures, specifying that crushed recycled materials may constitute no more than 30% of shoulder aggregate for new construction projects and up to 50% for existing granular shoulders. The specification addresses four primary material classifications: Class C Gravel, Class A Crushed Stone, Class B Crushed Stone, and Class D Crushed Stone, each with distinct gradation and quality requirements outlined in referenced aggregate gradation tables and materials testing methods. Material quality is assessed through standardized testing protocols including abrasion tests (AASHTO T 96), freeze-thaw resistance evaluation (Iowa DOT Materials Laboratory Test Method No. 211), and measurements of clay lumps, friable particles, and shale content. Class A Crushed Stone, which is the material specified for the District 6 Rock to Road procurement, must meet Gradation No. 11 requirements with maximum allowable abrasion of 45% (or 50% for granular shoulder aggregate only), C Freeze maximum of 15%, and clay lumps and friable particles not exceeding 4.0%.
The specification permits the use of recycled pavement concrete (PCC), recycled asphalt pavement (RAP), and composite pavement materials when processed to meet specific gradation and quality standards outlined in Materials I.M. 210. For granular shoulders, contract documents may authorize Class C gravel and crushed aggregate mixtures combining 30-50% crushed stone, 30-50% recycled crushed PCC or composite materials, and 30-50% RAP, provided each component meets designated gradation requirements with 8-16% passing the No. 200 sieve. The document includes detailed quality control tables specifying maximum percentages allowed for various contaminants and defects, with referenced test methods from Iowa DOT Materials Laboratory procedures and AASHTO standards. These specifications ensure consistency and durability of granular materials across Iowa DOT projects and establish the baseline technical requirements that vendors, including bidders on the District 6 Rock to Road procurement, must satisfy when supplying shoulder aggregate and related materials to the state.
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Text version
Section 4120. Granular Surfacing and Granular Shoulder Aggregate
4120.01 DESCRIPTION.
Uniform mixture of fine and coarse particles of crushed stone, gravel, or a combination of these materials with sand. Crushed recycled materials are to total no more than:
· 30% of the shoulder aggregate for new construction.
· 50% of the total for existing granular shoulders.
4120.02 GRANULAR MATERIAL.
A. Granular Surfacing.
Furnish material meeting the requirements of Article 4120.04, or when specified in the contract documents, meet the requirements of Article 4120.03, 4120.05, or 4120.06.
B. Granular Shoulders.
1. Furnish material meeting the requirements of Article 4120.04 or recycled materials. When specified in the contract documents, meet the requirements of Article 4120.05 or 4120.06. For recycled materials, meet the following requirements:
· Recycle PCC, RAP, or composite pavements to meet the requirements of Materials I.M. 210.
· Crush PCC or composite pavement to meet the requirements for Gradation No. 11 of the Aggregate Gradation Table, Article 4109.02.
· Process RAP to pass the 1.5 inch sieve.
2. The contract documents may allow a Class C gravel and crushed aggregate mixture for granular shoulders meeting the following:
· 30% to 50% crushed stone meeting soundness and abrasion requirements of Article 4120.05. Meet the requirements for Gradation No. 10 of the Aggregate Gradation Table, Article 4109.02 with the exception of 8% to 16% passing the No. 200 sieve.
· 30% to 50% recycled crushed PCC or composite materials meeting the above requirements for Granular Shoulders. Meet the requirements for Gradation No. 10 of the Aggregate Gradation Table, Article 4109.02 with the exception of 8% to 16% passing the No. 200 sieve.
· 30% to 50% RAP processed to pass the 1.5 inch sieve.
4120.03 CLASS C GRAVEL.
Meet the requirements for gradation No. 10 of the Aggregate Gradation Table, Article 4109.02 and Table 4120.03-1:
Table 4120.03-1: Coarse Aggregate Quality (Class C Gravel)
Coarse Aggregate Quality Maximum Percent Allowed Test Method
C Freeze 15 Iowa DOT Materials Laboratory Test Method No. 211, Method C
Shale (+ No. 4 sieve) 10 Materials I.M. 372
Total of Clay Lumps and Friable Particles, plus % passing No.
200 sieve
15 Materials I.M.s 368 and 306
Total of Shale, Clay lumps and friable particles, plus % passing.
No. 200 sieve
20 Materials I.M.s 372, 368, and 306
4120.04 CLASS A CRUSHED STONE.
Meet the requirements for Gradation No. 11 of the Aggregate Gradation Table, Article 4109.02 and Table 4120.04-1:
10/23/25, 10:33 AM Section 4120 | Revised 10/21/2025 https://ia.iowadot.gov/erl/current/GS/content/4120.htm 1/2 https://ia.iowadot.gov/erl/current/GS/IM/content/210.htm https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902 https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902 https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902 https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902 https://ia.iowadot.gov/erl/current/GS/IM/content/372.htm https://ia.iowadot.gov/erl/current/GS/IM/content/368.htm https://ia.iowadot.gov/erl/current/GS/IM/content/306.htm https://ia.iowadot.gov/erl/current/GS/IM/content/372.htm https://ia.iowadot.gov/erl/current/GS/IM/content/368.htm https://ia.iowadot.gov/erl/current/GS/IM/content/306.htm https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902
Table 4120.04-1: Coarse Aggregate Quality (Class A Crushed Stone)
Allowed Test Method
Abrasion 45 AASHTO T 96
C Freeze 15 Iowa DOT Materials Laboratory Test Method No. 211, Method C
Clay Lumps and Friable Particles 4.0 Materials I.M. 368
Note: For Granular Shoulder Aggregate only, the abrasion limit is 50.
4120.05 CLASS B CRUSHED STONE.
Meet the requirements for Gradation No. 11 of the Aggregate Gradation Table, Article 4109.02 and Table 4120.05-1:
Table 4120.05-1: Coarse Aggregate Quality (Class B Crushed Stone)
Allowed Test Method
Abrasion 55 AASHTO T 96
C Freeze 20 Iowa DOT Materials Laboratory Test Method No. 211, Method C
Total of Abrasion & C Freeze 65
Clay Lumps and Friable Particles 4 Materials I.M. 368
4120.06 CLASS D CRUSHED STONE.
Refer to the contract documents for gradation and quality requirements.
4120.07 AGGREGATE FOR PAVED SHOULDER FILLETS.
Crushed stone or recycled materials meeting the requirements for Gradation No. 11 of the Aggregate Gradation Table, Article 4109.02, and meeting the quality requirement of Article
4120.04. For recycled materials, meet the requirements of Article 4120.02, B.
10/23/25, 10:33 AM Section 4120 | Revised 10/21/2025 https://ia.iowadot.gov/erl/current/GS/content/4120.htm 2/2 https://ia.iowadot.gov/erl/current/GS/IM/content/368.htm https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902 https://ia.iowadot.gov/erl/current/GS/IM/content/368.htm https://ia.iowadot.gov/erl/current/GS/GS/content/4109.htm#Section410902
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