214Lime Treated Subgrade

Lime Treated Subgrade

214.1DESCRIPTION

1 This section describes the requirements for constructing one or more courses of a mixture of soil, lime, and water.

214.2MATERIALS

1 Provide materials in accordance with the following:

Materials Subsection Hydrated Lime 820 Water 814.1

2 Use existing subgrade soil or approved borrow material, as specified, with deleterious materials removed.

214.3EQUIPMENT

214.3.1 General

1 Correct equipment leaks immediately, or remove the equipment from the work area.

214.3.2 Lime Spreaders

1 Use lime spreading equipment capable of spreading lime uniformly at the specified rate and keeping the slurried lime in suspension.

214.3.3 Water Distribution

1 Use equipment capable of uniformly distributing the required water. Do not use water pumps on water distributors.

214.3.4 Mixing

1 Use a self-propelled rotary mixer, except that disc harrows, motor graders, and other equipment may be used to supplement the mixing performed by the rotary mixer. Use mixing equipment capable of mixing to a compacted depth of at least 10 in [250 mm].

2 Provide a traveling mixing plant for incorporating the lime into the soil designated for treatment. Ensure that the traveling mixing plant is capable of spreading the lime slurry in an even, traverse layer, providing a homogeneous mixture of lime and subgrade, and

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metering the lime at the desired application rates for the volume of material to be treated per layer.

214.3.5 Compaction

1 Use compaction equipment that is self-propelled. Finish roll with a pneumatic tire roller, a smooth steel-wheeled roller, or a combination of both.

214.4CONSTRUCTION

214.4.1 General

1 Perform lime stabilization when the air temperature is 45 °F [10 °C] or above. Do not mix the lime with frozen soils or soils containing frost . Do not apply lime when wind conditions are such that excessive loss of lime occurs or when blowing lime becomes hazardous to traffic, workers, or adjacent property owners.

214.4.2 Soil Preparation

1 Shape the subgrade surface of the prepared roadbed subgrade to be treated to the staked lines, grades, and cross section. Excavate subgrade material in cut sections to the required depth, and incorporate excavated material into the roadway embankment. Place excavated subgrade material in a windrow adjacent to the section to be treated, stockpile, or waste.

2 When lime treatment depth is more than the contractor’s equipment is capable of handling, excavate material above the bottom layer to be treated in excess of what the contractor’s equipment can treat, and place it in a windrow or stockpile. When practical, place the excavated material in a windrow adjacent to the area to be treated, and place it on the roadway as each treated layer is completed.

3 Cut drains through the shoulders adjacent to the excavated areas to drain the roadbed. Cut drains through the windrows at sufficient intervals to prevent ponding of water . Move the windrows when necessary to allow the subgrade to dry.

4 Scarify the subgrade to be lime treated to the specified depth and width and partially pulverize it. Control the depth of scarification to ensure that the surface of the roadbed below the scarified material remains undisturbed and matches the required cross section. Before the stabilization work, remove unsuitable material including stones retained on a 3 in [75 mm] sieve.

214.4.3 Application of Lime

214.4.3.1 General

1 Apply the lime dry or as a slurry at the specified rate. Base the volume of lime on air-dry

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weight [mass], and calculate the spread as the quantity of lime required for each square yard [square meter] of treated surface for each compacted layer.

2 Allow only the equipment needed for the lime treatment operations on the applied lime before mixing is completed.

3 Immediately discontinue procedures that result in displacement of the lime.

214.4.3.2 Dry Application

1 If the dry process is used, take necessary precautions to minimize the amount of air- borne hydrated lime.

214.4.3.3 Lime Slurry Application

1 Adjust lime slurry proportions and application rates so that the specified application rate of lime is maintained while meeting moisture content requirements. When necessar y, process materials to be treated so that the existing moisture content is adjusted sufficiently to allow the addition of moisture from the lime slurry.

2 When approved by the engineer, lime slurry may be applied directly to the subgrade materials to be treated. Before approval, submit a detailed plan for lime slurry application in writing. Include equipment to be used in spreading the lime slurr y, anticipated lime slurry proportions, and mixing and delivery methods in the plan.

214.4.4 Mixing

1 Immediately after the lime has been spread, mix it thoroughly into the soil with water added as necessary for the full depth of treatment. Incorporate the lime thoroughly and uniformly into the soil layer to the full depth of treatment so that the result is a homogenous, friable mixture of soil and lime. Mix the lime by a traveling mixing plant with a single pass to the depth specified.

2 Place and compact the lime treated material within 48 hours after mixing. When it is not practical to place the mixed material within 48 hours, place it in a windrow, or spread it over the road and seal the surface with a steel-wheel or pneumatic-tired roller to prevent the loss of moisture.

214.4.5 Placing, Compacting, and Finishing

1 After mixing each layer of material, place them in the approximate section and compact to a density of at least 95.0 percent of the maximum density at a moisture content of plus or minus 2 percent of optimum. A light sprinkling with water may be required during placement operations to maintain the specified moisture content.

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2 Accompany compaction by finish grading work to eliminate irregularities and maintain the staked lines, grades, and cross section.

3 When, after treatment, additional subgrade materials need to be added to the grade to reach the staked lines and grades, use lime treated materials. Lightly scarify the surface of the treated subgrade before placing additional material required for finish grading. Process and compact the subgrade materials in accordance with the requirements described in this section, Section 214.4.5, Placing, Compacting, and Finishing.

4 Lightly scarify and grade the surface of the final layer during finishing operations to eliminate imprints left by the equipment. Use a roller with pneumatic tires to make the final roll on the completed surface.

214.4.6 Protection and Curing

1 When compaction and finish grading are completed, cure the treated subgrade for a minimum of 24 hours before allowing highway traffic and construction equipment on the lime treated subgrade. Repair damage to the treated subgrade due to traffic and construction equipment.

214.5MEASUREMENT and PAYMENT

214.5.1 General

1 The engineer will measure:

yard [square meter]. Each roadway of a divided highway will be measured separately for payment. When treatment by the square yard [square meter] is specified, the measurement will be made on the top surface area of each layer treated, excluding shoulder slopes.

2 The department will pay as follows:

Pay Item

Pay Unit Measure to the Nearest Pay to the Nearest Hydrated Lime (Subgrade) TON [t] 0.05 ton [0.05 t] TON [t] Processing (Lime Treated Subgrade) STA, FT, SY [0.005 Sta, m, m2]

0.05STA, ft, 0.1 ft

[0.001 Sta, 0.5 m, 0.05 m]

STA, FT, SY

[0.5 Sta, m, m2]

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214.5.2 Referenced Sections for Direct Payment

1 When specified, the engineer will measure and pay for:

Embankment, for materials that have proven to be untreatable and are removed upon approval of the engineer.