Section 4125 specifications.pdf

This is a specification document issued by the Iowa Department of Transportation (Iowa DOT) detailing technical requirements for aggregate materials used in bituminous sealcoat applications on state roadways. Section 4125 establishes comprehensive standards for crushed stone, gravel, and sand products, including mandatory washing requirements and differentiated specifications based on road classification. The specification identifies four primary gradation categories: 1/2 inch crushed gravel or stone (Gradation No. 19), screened gravel (Gradation No. 20), 3/8 inch crushed gravel or stone (Gradation No. 21), and sand cover aggregate (Gradation No. 1), with provisions allowing 1/2 inch materials to substitute for 3/8 inch specifications in non-Primary Road applications. Crushed aggregate is mandatory for primary and interstate roadways and may be required for other projects; crushed gravel must be produced as a separate operation by crushing particles retained on a screen at least 1/4 inch larger than the specified aggregate size.

Quality standards mandate that all aggregate materials be free from objectionable clay coatings that prevent proper emulsion coating and must achieve Type 4 or better frictional classification per Materials I.M. T203. Cover aggregate for bituminous sealcoat must meet specific maximum allowances for defects: abrasion at 40 percent (AASHTO T 96 C), freeze damage at 10 percent (Office of Materials Test Method No. Iowa 211, Method C), shale particles greater than No. 4 sieve at 5.0 percent, and shale particles greater than No. 16 sieve for sand cover aggregate at 2.0 percent. For crushed stone products, materials passing the No. 200 sieve are permitted up to 4 percent. All testing and verification of compliance must be conducted using the specified Iowa DOT materials test methods and AASHTO standards referenced in the document.