302.01 210 SECTION 302 – SUBGRADE TREATMENT (LIME)
302.01 De scription ................................ ................................ ................... 210
302.02 Reserved ................................ ................................ ....................... 210
302.03 Material s ................................ ................................ ...................... 210
302.04 Equipment ................................ ................................ .................... 211
302.05 Limitations ................................ ................................ ................... 212
302.06 Preparing the Existing Subgrade ................................ .................. 212
302.07 Extra Depth Stabilization ................................ ............................. 213
302.08 Applying Lime ................................ ................................ ............. 213
302.09 Initial Mixing and Mellowing ................................ ...................... 214
302.10 Final Mixing ................................ ................................ ................. 214
302.11 Compaction and Finishing ................................ ........................... 215
302.12 Curing ................................ ................................ .......................... 216
302.13 Tolerances and Reconstruction ................................ .................... 216
302.14 Method of Measurement ................................ .............................. 217
302.15 Basis of Payment ................................ ................................ .......... 219
DESCRIPTION
302.01 Description
This work consists of treating in -place subgrade material with lime, and includes preparing the existing subgrade, distributing the specified percentage of lime, initial mixing, mellowing, final mixing, compacting, finishing, and curing.
302.02 Reserved
MATERIALS
302.03 Materials
A.Lime Provide either hydrated lime or quicklime meeting 921.04. 302.04 211 B. Water Only use water that meets the requirements of 921.01.
C.Soil Use in-place subgrade material, removing unsuitable soil and replace it with suitable material. Before the work is started, sample the in -place material and perform laboratory testing to determine the percentage of lime required and the appropriate optimum moisture content of the lime -soil mixture according to AASHTO T 99, Method C. Submit the design to the Department for approval.
D.Bituminous Material For use as a curing agent, provide bituminous material as specified in: PG64-22, 70-22, 76-22, and 82-22 ................................ ........ 904.01 Emulsified Asphalt, Types allowed for Tack Coat in 403 ............................... 904.03 Provide emulsified asphalt, of a type allowed for Tack Coat in 403, meeting the test requirements specified in Table 904.03-1. The Contractor may select the type of bituminous material to use for curing. EQUIPMENT
302.04 Equipment
A.Distributing Equipment Provide equipment to distribute the lime uniformly, at the required rate and without excessive loss.
B.Mixers Provide an acceptable mixer capable of attaining final mixing specified in 302.10. 302.06 212 C. Compaction Equipment Provide compaction equipment of the size and weight required to obtain the specified density and quality of finished surface. CONSTRUCTION REQUIREMENTS
302.05 Limitations
Handle and store lime in completely enclosed, moisture resistant containers until immediately before use. Store bagged lime in weatherproof buildings with adequate protection from ground dampness. Do not stabilize areas that will not be covered with the succeeding stage of sub-base or base construction during the same construction season. Do not apply lime:
1.to frozen subgra de material;
2.if the air temperature in the shade is less than 40 °F;
3.during periods of high winds; and
4.to areas that cannot be mixed and sealed as specified in 302.09 on the same day as application. Do not leave lime e xposed to the open air for a period of 6 hours or more. Do not allow traffic or equipment on the spread lime other than that required for spreading, watering, or mixing.
302.06 Preparing the Existing Subgrade
Grade and shape the existing roadway in reasonably close conformity with the lines, grades, and cross -sections shown on the Plans or as directed by the Engineer. Remove all grass turfs and other deleterious substances from the subgrade and prepare the subgrade as specified in 207.03. Correct wet or unstable underlying foundation material, if encountered, as directed by the Engineer. 302.07 213 302.07 Extra Depth Stabilization If directed by the Engineer, perform extra depth lime stabilization as follows:
1.Blade the overlying material to the sides, and incorporate the lime slurry or, in dry applications, the hydrated lime and any necessary water, into the underlying material at the rate and to the depth specified.
2.Thoroughly mix and compact the lime -soil mixture to obtain the required stability.
3.Moisten the compacted surface, and cover with the previously windrowed subgrade material.
4.Compact the overlying subgrade material, which will serve as the curing medium. Curing and mellowing periods will not be required for the lime -stabilized underlying material unless otherwise directed by the Engineer.
302.08 Applying Lime
After preparing the subgrade as specified in 302.06, apply lime using the dry or slurry application metho d for either hydrated lime or quicklime. Use the slurry application method unless otherwise shown on the Plans.
A.Dry Application Spread hydrated lime at the required rate, using an approved spreader that will uniformly distribute the material without exces sive loss, or by bag distribution.
B.Slurry Preparation and Application Mix lime with water in approved agitating equipment, and apply to the roadway as a thin water suspension or slurry through approved distributing equipment. The distributing equipment shall be equipped to continuously agitate the mixture from the mixing site until applied on the roadbed. Proportion the mixture so that the dry solids content is at least 30% by weight. 302.09 214 In preparing, transporting, distributing, and mixing slurry with the soil, do not cause injury, damage, discomfort, or inconvenience to individuals or private property.
302.09 Initial Mixing and Mellowing
In dry applications, immediately after applying the hydrated li me, scarify the course, if necessary, and mix to the required depth, width, and cross -sections. In slurry applications, before applying the lime slurry, scarify or partially pulverize with approved mixing equipment the full width of the course to be treated, as directed by the Engineer, to the depth required for stabilization. Perform successive passes over a measured section until the specified percentage of lime has been distributed. After each successive pass, incorporate the slurry into the soil with approved mixing equipment. Incorporate lime into the soil to the depth needed to provide a finished course of lime-treated material conforming to the specified thickness and surface requirements. Continue mixing, and applying water as necessary, until a ho mogeneous mixture of soil, lime, and water is obtained. During this initial mixing operation, add the quantity of water needed for the moisture content of the mixture to reach 5% above its optimum moisture content, plus or minus 3%, unless otherwise direc ted by the Engineer. If applying the lime as a slurry, ensure that the water added with the slurry does not cause the moisture content of the lime -soil mixture to exceed the above tolerance. After completing mixing operations, reshape the treated course to the approximate lines, grades, and cross -sections, and seal with a pneumatic -tire roller, and other approved equipment as necessary, and allow the treated course to mellow for 2 to 7 days as directed by the Engineer. During the mellowing period, maintain the entire surface of the treated course in a moist condition.
302.10 Final Mixing
After the required mellowing period, reshape and grade the initially mixed material to the required lines, grades, and cross -sections. 302.11 215 Thoroughly mix the previously mixed material with approved mixers while adding water as necessary. Continue mixing until 100% of the material, except for gravel and stone, will pass a 1-inch sieve, and 60% by dry weight will pass the No. 4 sieve. The quantity of water added shall be such that at the end of the final mixing and during compaction and finishing operations the percentage of moisture in the mixture and the unpulverized soil lumps will not vary more than plus or minus 3% from the specified opti mum moisture of the lime -soil mixture.
302.11 Compaction and Finishing
Immediately after completing the final mixing, blade the material to uniform thickness and shape, and start compaction operations. Us e sheepsfoot rollers to compact the material in a continuous operation until the entire depth of the lime-soil mixture is uniformly compacted to the required density. The Contractor may remove the sheepsfoot rollers when a surface mulch not exceeding 1 in ch remains. Lightly scarify the resulting surface and shape to the required lines, grades, and cross -sections within the tolerances specified in 302.13. Perform final rolling with the roller specified by the Engineer. The completed lime stabilized subgrade shall be smooth, dense, well bonded, unyielding, and free of cracks or loose material. Compact the lime -soil mixture in layers as shown on the Plans. The Department will determine the maximum density and optimum moi sture content of the lime -soil mixture according to AASHTO T 99. The sample used to determine the maximum density and optimum moisture content will be representative field samples of the lime -soil mixture that have undergone the same treatment as the lime treated subgrade being tested. For density testing purposes, the Department will divide the completed subgrade treatment into lots of approximately 10,000 square yards, and will perform five density tests on each lot. The average dry density of each lot shall not be less than 95% of maximum density, and no individual test shall be less than 92% of maximum density. Immediately scarify, moisten (if required), rework, and compact to the required density all areas that do not meet density requirements at no additional cost to the Department. 302.12 216 302.12 Curing After finishing the lime -treated subgrade as specified in 302.11, seal the surface by applying one of the bituminous materials specified in 302.03.D using a pressure distributor at the rate of 0.10 to 0.25 gallons per square yard, as directed by the Engineer or as shown on the Plans. Heat or otherwise prepare the bituminous material to ensure uniform distribution and a pply as soon as possible.
302.13 Tolerances and Reconstruction
The Department will determine the thickness of the completed lime -treated subgrade by measuring test holes at random locations as specified in Departmental procedures . The measured thickness at the locations shall not deviate from that shown on the Plans by more than pl us 1-1/2 inches or minus 1 inch. Immediately reconstruct areas of lime -treated subgrade that do not meet thickness requirements. For areas having a thickness greater than that allowed, add sufficient lime to correct the deficiency in lime content. Perform reconstruction, including adding lime, to correct the thickness deviation at no cost to the Department. As directed by the Engineer, repair areas of lime -treated subgrade that become unstable or that lose the required density or surface finish. Use additional lime and water if and as directed. Limit hauling over the treated subgrade to the minimum amount necessary to construct the overlying base or sub -base. When at least one course of base or sub -base has been constructed upon the treated subgrade, the Contractor may resume hauling, provided the layer or layers of base or sub -base are constructed and maintained as specified in
303.10 and 303.11.
302.14 217 COMPENSATION
302.14 Method of Measurement
A.Lime The Department will measure Lime by the ton. Quantities and percentages of lime shown on the Plans are based on preliminary soil investigations and dry laboratory sample tests using hydrated lime. The Engineer will establish the actual application rate from dr y density tests conducted just before the start of stabilization work. For quicklime, the Department will determine the accepted quantity by converting the quicklime to an equivalent quantity of hydrated lime as follows: EHL = 1.32 QL [1 - I 100] Where: EHL = Equivalent amount of hydrated lime in tons QL = Tons of quicklime accepted I = Percent of impurities in the quicklime The Department will deduct for quantities of lime that have been wasted or not actually used in the work. If sacked lime is used, the Department will use the net weight as packed by the manufacturer for measurement.
B.Processing of Subgrade Treatment (Lime) The Department will determine the area processed by the square yards of treated subgrade, as computed using the length measured at the surface of the treated subgrade and the width shown on the Plans or designated by the Engineer.
C.Extra Depth Stabilization
1.Direction Application Method. The Department will classify processing performed using the Direct Application Method, as specified in 302.07, as Subgrade Treatment, and will measure this work for payment as follows: 302.14 218 a. If the thickness of the layers processe d is equal to or greater than the Plan thickness for normal stabilization, the Department will measure processing by the square yard s of each extra depth layer processed.
b.If the thickness of the layers processed is less than the Plan thickness for norma l stabilization, the Department will measure the area in square yards of each extra depth layer processed and will adjust this area to determine the quantity for payment by multiplying the number of square yards processed by the thickness of the layer and dividing by the Plan thickness for normal stabilization. To determine the area of extra depth layers , the Department will measure the length and width used in accordance with
302.14 B.
2.Drill-Lime Method. The Department will measure drilling necessary to complete Extra Depth Stabilization by the total quantity in linear feet of all holes drilled, from either the finished subgrade or from the top of base to the bottom of the drilled holes.
D.Water The Department will measur e water by the M.G. (1,000 gallons ) using calibrated tanks or distributors, or accurate water meters. The quantity measured for payment will be the amount necessary for subgrade preparation, initial mixing, mellowing, final m ixing, compacting, finishing, and curing. The Department will not measure water used to prepare or apply slurry.
E.Bituminous Material The Department will measure in tons the quantity of bituminous material used and accepted.
F.Preparation of Existing Subgra de The Department will classify and measure the m aterials moved, furnished , or disposed of to prepare the subgrade in accordance with
302.06 as provided for under 207.
302.15 219 302.15 Basis of Payment The Department will pay for accepted quantities at the contract prices as follows: Item Pay Unit Hydrated Lime Ton Bituminous Material Ton Soil-Lime Processing Square Yard Drilling for Subgrade Treatment Linear Feet Water M.G. Such payment is full compensation for providing all materials, equipment, labor, and incidentals to complete the work as specified. The Department will pay for moving, furnishing, or disposing of material under 207 if the Contract is for any of the following:
1.Combined grading, drainage and paving project,
2.Construction of a base and/or pavement on a road that has been graded under a previous Contract, or
3.Base and/or paving project that includes sections of grading. For Extra Depth Stabilization , the Department will not pay for any shifting of the overlying material ; however, the Department will pay for t he lime and water used and for the mixing of the underlying material with the lime and water. If repairs to the lime -treated surface are made necessary by a cause beyond the Contractor’s control, the Department will pay for the construction items involved at the contract unit prices. 303.01 220 SECTION 303 – MINERAL AGGREGATE BASE
303.01 Description ................................ ................................ ................... 220
303.02 Aggregate ................................ ................................ ..................... 220
303.03 Calcium Chloride ................................ ................................ ......... 221
303.04 Reserved ................................ ................................ ....................... 221
303.05 Emulsified Asphalt ................................ ................................ ....... 221
303.06 Equipment ................................ ................................ .................... 221
303.07 General ................................ ................................ ......................... 222
303.08 Mixing ................................ ................................ .......................... 223
303.09 Spreading ................................ ................................ ..................... 224
303.10 Shaping and Compaction ................................ ............................. 225
303.11 Maintenance ................................ ................................ ................. 227
303.12 Thickness Requirements ................................ .............................. 227
303.13 Surface Requirements ................................ ................................ .. 227
303.14 Method of Measurement ................................ .............................. 228
303.15 Basis of Payment ................................ ................................ .......... 229
DESCRIPTION
303.01 Description
This work consists of furnishing and placing one or more courses of aggregates, and additives if required, on a prepared subgrade. Mineral aggregates base shall be Type A or Type B, whichever is shown on the Plans and called for in the bid schedule. Recycled Concrete Aggregate (RCA) may be used as an alternate for Type A or Type B base material. MATERIALS
303.02 Aggregate
Depending upon whether the Plans require Type A or Type B base, provide mineral aggregate meeting 903.05. For Type A base, use aggregate of Grading D. For Type B base, the Contractor may use aggregate of Grading C or D. For RCA, use grading specified in 903.05.C.
Source: Tennessee Standard Specifications for Road and Bridge Construction, 2021 Edition. Pages 219–228 of 1,072.