209Subgrade Construction

209.1 General Description

This work includes placing, mixing, compacting, and shaping the top 6 in. (150 mm) or the plan-indicated thickness of the roadbed in both excavation and embankment areas. This work also includes subgrade stabilization, select material subgrade, and shoulder stabilization.

209.1.01 Definitions

General Provisions 101 through 150.

209.1.02 Related References

A. Standard Specifications Section 109—Measurement and Payment Section 412—Bituminous Prime Section 803—Stabilizer Aggregate Section 810—Roadway Materials Section 815—Graded Aggregate B. Referenced Documents GDT 7 GDT 20 GDT 21 GDT 24a GDT 24b GDT 59 GDT 67

209.1.03 Submittals

General Provisions 101 through 150.

209.2 Materials

A. Subgrade Materials If the Plans do not show the source of material for subgrade, the Engineer will direct the Contractor according to the specifications or implement a Supplemental Agreement to ensure a satisfactory subgrade. If the existing roadway excavation or borrow materials are not suitable or available for stabilizing the subgrade, use the quantity of stabilizer materials defined below in Subsection 209.2.B. B. Subgrade Stabilizer Materials Material Section Type I Stabilizer Aggregate 803.2.01 Type II Stabilizer Aggregate 803.2.02 Class IIB3 or Better Soil 810.2.01.A.1 Type III Stabilizer Aggregate 803.2.03 Type IV Stabilizer Sand 803.2.04 C. S elect Material Subgrade Material Section Class IIB3 or Better Soil in Districts 2, 3, 4, and 5

810.2.01 A.1

Class IIB4 or Better Soil in Districts 1, 6, and 7

810.2.01 A.1

Class IIIC4, chert clay soils in District 6 with less than 55% passing the No. 10 (2 mm) sieve

810.2.01 A.1

Graded Aggregate 815 D. S houlder Stabilization Material Section Shoulder Stabilization 803.2.02, Type II 09.2.01 Delivery, Storage, and Handling General Provisions 101 through 150.

209.3 Construction Requirements

209.3.01 Personnel

General Provisions 101 through 150.

209.3.02 Equipment

General Provisions 101 through 150.

209.3.03 Preparation

General Provisions 101 through 150.

209.3.04 Fabrication

General Provisions 101 through 150.

209.3.05 Construction

A. Subgrade Construction Construct subgrade as follows: 1. Plow, harrow, and mix the entire surface of the in-place subgrade to a depth of at least 6 in. (150 mm). 2. After thoroughly mixing the material, bring the subgrade to Plan line and grade and compact it to 100 percent o f the maximum laboratory dry density. 3. If the subgrade needs to be stabilized, or if a subsequent contract provides for base construction, do not ap ply density requirement at this stage. If a subsequent Contract provides for base construction, eliminate mixing and compact the in-place subgrade to 95 percent of the laboratory maximum dry density. 4. that the subgrade can firmly support construction equipment before placing subsequent layers of base and paving materials. The subgrade must support construction equipment without excessive movement r egardless of compaction. 5. Rework unstable areas of subgrade to a moisture content that will provide stability and compaction. The E ngineer may direct the Contractor to proof roll the subgrade with a loaded dump truck. 6. Compact the subgrade using a sheepsfoot roller. The Engineer may permit the use of vibratory rollers whenever the subgrade soils consist of Class IaA1, IA2, or IA3 materials. 7. Ensure that subgrade material used underneath soil-cement base Ensure meets the requirements of S ubsection 301.3.03.A. B. Subgrade Stabilization Construct a stabilized subgrade according to Plans or as directed: 1. Undercut and dispose of the amount of subgrade material that will be displaced with the aggregate or selected material according to the Engineer’s direction. 2. Leave material off the subgrade in fill sections requiring stabilization. 3. Place the amount of material specified in Subsection 209.2.B. on the subgrade as specified on the Plans or established by the Engineer. 4. Thoroughly incorporate the material into the existing subgrade to a depth of 6 in. (150 mm), or as indicated on the plans. Plow, disk, harrow, blade, and then mix with rotary tillers until the mixture is uniform and homogeneous throughout the depth to be stabilized. 5. Finish the stabilized subgrade to the plan line, grade, and cross-section. Compact it to 100 percent of the maxi mum laboratory dry density as defined in Subsection 209.3.06. Plant mixing is permitted as an alternative to the mixed-in-place method. 6. Eliminate the mixing and scarifying method before compaction in undercut areas where Type III Stabilizer Aggregates are specified, unless otherwise specified by the Engineer. C. Select Materials Subgrade Place select materials as follows: 1. Place the subgrade with a uniform blanket of select material consisting of Class I or II soil or graded aggregate (according to Plan dimensions or as directed by the Engineer). Class IIIC1 soils may be used in Districts 1, 6, and 7 within the top 12 in. (300 mm) of subgrade if approved by the Office of Materials and Testing, Geotechnical Environmental Pavement Bureau. Do not use Class IIIC2, IIIC3, or IIIC4 soils within the top 12 in. ( 300 mm) of subgrade unless a stabilizing agent approved by the Engineer is added, or if approved by the O ffice of Materials and Testing, Geotechnical Environmental Pavement Bureau. Class IIIC4, chert clay soils in D istrict 6 with less than 55 percent passing the No. 10 (2 mm) sieve may be used for subgrade. 2. Use the select material reserved from the grading or borrow operations. If material is not available through this s ource, obtain it from other sources. 3. Finish and compact the material according to Subsection 209.3.05.A. D. Shoulder Stabilization Stabilize the shoulder as follows: 1. Spread the stabilizer aggregate at the rate and to the dimensions indicated on the Plans. 2. Mix the aggregate with the in-place shoulder material thoroughly to the Plan depth. 3. Compact the area thoroughly and finish it to Plan dimensions. 4. Prime the stabilized area according to Section 412 when a paving course is required on the shoulders. E. Finishing Subgrade When finishing subgrade use the following procedure: 1. Leave the underlying subgrade in cuts and fills low enough to accommodate the additional material when the wo rk requires either subgrade stabilization, select material subgrade, or stabilization for shoulders. 2. Test short sections in curb and gutter areas might be necessary to obtain the proper elevation. 3. Blade the surface of the completed subgrade to a smooth and uniform texture.

209.3.06 Quality Acceptance

The Department will test representative samples of compacted material to determine the laboratory maximum dry density using GDT 7, GDT 24a, or GDT 67 as applicable. The Department will determine in-place density of the compacted subgrade according to GDT 20, GDT 21, or GDT 59, as applicable. Ensure that the centerline profile conforms to the established elevations with an acceptable tolerance of ±0.5 in (±13 mm). The acceptable tolerance under a template conforming to the designated cross section shall be ±0.25 in. (±6 mm). Have the Department test the maximum dry density using methods according to Subsection 209.3.05.A. When base construction is not in the same Contract, the tolerances may be 1 in. (25 mm), 0.5 in. (13 mm), and 95 percent respectively.

209.3.07 Contractor Warranty and Maintenance

General Provisions 101 through 150.

209.4 Measurement

A. Subgrade Construction and Finishing Subgrade The Department will make no separate measurement or payment for the work described in this Section. B. Subgrade Stabilization Subgrade stabilization materials, as defined in Subsection 209.3.05.B is measured by the ton (megagram), cubic y ard (meter), or square yard (meter) of the specified thickness if none of the existing Roadway Excavation and/or B orrow Materials are suitable and available for stabilizing the subgrade. C. Select Material Subgrade Select materials, conforming to Subsection 209.3.05.C are measured by the cubic yard (meter) in the hauling vehicle, per ton (megagram) according to Subsection 109.01, or by the square yard (meter) of the specified thickness when roadway excavation and/or borrow materials are not available or suitable for this Item. D. Shoulder Stabilization Shoulder stabilization is measured by the cubic yard (meter) or ton (megagram) as specified in Subsection 209. 4.B.

209.4.01 Limits

General Provisions 101 through 150.

209.5 Payment

A. Subgrade Construction The Department will make no separate payment for subgrade construction or for finishing subgrade. B. Subgrade Stabilization Subgrade stabilization complete and accepted according to Subsection 209.3.05.B will be paid for at the Contract U nit Price per cubic yard (meter), per ton (megagram), or per square yard (meter). This price is full compensation fo r furnishing the materials, hauling, placing, mixing, compacting, and finishing the stabilized subgrade. C. Select Material Subgrade Select material complete, accepted, and measured according to Subsection 209.4.C will be paid for at the C ontract Unit Price per cubic yard (meter), per ton (megagram), or per square yard (meter). This price is full compensation for furnishing the material where required, hauling, placing, mixing, compacting and finishing the s elect material subgrade. D. Shoulder Stabilization This Item will be measured by Subsection 209.4.B. and paid for according to Subsection 209.5.B. This Item also includes furnishing and applying bituminous prime. Payment will be made under: Item No. 209 Stabilizer materials (class), (type), (thickness) Per ton (megagram), cubic yard (meter), or square yard (meter) Item No. 209 Select material subgrade (class), (type), (thickness) Per ton (megagram), cubic yard (meter), or square yard (meter) Item No. 209 Stabilizer aggregate for shoulders Per ton (megagram), or cubic yard (meter)

209.5.01 Adjustments

General Provisions 101 through 150.