812Backfill Materials

812.1General Description

This section includes the requirements for four types of material used as backfill: foundation backfill, Types I and II, imperfect trench backfill, Type III, and mechanically stabilized wall backfill. 812.1.01 Related References

AASHTO T 11 AASHTO T 27 AASHTO T 96 AASHTO T 104 GDT 4 GDT 6 GDT 7 GDT 24a GDT 24b GDT 67 GDT 75 GDT 98 SOP 1

812.2Materials

812.2.01 Foundation Backfill, Type I

Use natural or artificial mixtures of materials consisting of hard, durable particles of sand or stone, mixed with silt, clay and/or humus material for Type I backfill. Have the final blend of material meet the requirements of Class I or II soils in Subsection 810.2.01.

General Provisions 101 through 150. 1478 1478 1478

Test as follows: Test Method Soil gradation GDT 4 Volume change GDT 6 Maximum density GDT 7 or GDT 67

General Provisions 101 through 150. 812.2.02 Foundation Backfill, Type II

Type Use material meeting the requirements of Section 800, Class A or B aggregate, and SOP 1. Crushed concrete may be used provided it meets the requirements of Section 800 that are applicable to Group 2 Aggregates. Do not use backfill aggregate containing soil or decomposed rock. Gradation Use material meeting the following gradation requirements: Sieve Size % Passing by Weight 1-1/2 in. (37.5 mm) 100 1 in. (25 mm) 80-100 No. 8 (2.36 mm) 0-5

General Provisions 101 through 150.

Test as follows: Test Method Sieve analysis AASHTO T 27

General Provisions 101 through 150. 812.2.03 Imperfect Trench Backfill, Type III

Type Use material made from either of the following for Type III backfill: • A natural soil with a density of less than 95 lb./ft.³ (1520 kg/m³) when tested with GDT 7 • An artificial mixture of soil and organic material, such as hay, leaves, or straw 1479 1479 1479

General Provisions 101 through 150.

The laboratory will: Test the soil density with GDT 7. Review the mixture and the percentages of each material and approve a mixture suitable for the project.

General Provisions 101 through 150. 812.2.04 Mechanically Stabilized Embankment Backfill

Use material comprised of crushed stone, natural sand, or a blend of crushed stone and natural sand free of soils, organic or any other deleterious substances meeting the following additional requirements: Crushed Stone Use a material manufactured from Class A or B stone that is free of soil overburden, has a soundness loss of not more than 15 percent, and conforms to the requirements of SOP 1. Natural Sand May be used in conjunction with an approved, non-corrodible, extensible reinforcement. Use non-plastic material consisting of strong, hard, durable particles having a durability index of at least 70. Use Natural Sand from an approved source on Qualified Products List – 1 or from a source approved by the Office of Materials and Testing. Requirements for approval will be provided by the Geotechnical Bureau. Gradation Sieve Size % Passing by Weight 4 in. (100 mm) 100 2 in. (50 mm) 80 -100 No. 10 (2 mm) 20 - 90* No 200 (75 µm) 0 - 15 * Natural Sand may be 20 - 100 1480 1480 1480

Chemical Ensure the material meets the following chemical requirements: Test Method Requirement pH *5.0 – 9.5 Resistivity >3000 ohms/cm Chlorides <100 ppm Sulfates <200 ppm Note: These chemical requirements are not applicable to MSE walls stabilized with an approved, non-corrodible, extensible reinforcement. *Sources of select backfill material having a pH between 4.5 and 5.0 may be used provided the interior face of the MSE wall panels have 3 inches of concrete cover over the reinforcemen t and the concrete used in the panels contains the following ingredients and proportions: Material % by Weight Minimum Maximum Cement 30 -- Type F Fly Ash 10 20 Slag 50 60 Type F Fly Ash and Slag -- 70 Maximum Dry Density Use backfill material with a maximum dry density equal to or greater than the design unit weight shown on the plans.

General Provisions 101 through 150. 1481 1481 1481

Test the material as follows:

General Provisions 101 through 150. Test Method Requirement Percent Wear AASHTO T96 (“A” Grading) Sieve Analysis AASHTO T 27 Material Passing No. 200 (75 µm) Sieve AASHTO T 11 Durability Index GDT 75 Maximum Dry Density GDT 7 or GDT 24a, GDT 24b Soundness (Magnesium Sulfate) AASHTO T 104 pH GDT 98 Resistivity GDT 98 Chlorides GDT 98 Sulfates GDT 98 1482 1482 1482