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The work covered by this section consists of treating the subgrade, embankment, natural ground, or existing pavement structure by adding water and lime in the form specified herein, mixing, shaping, compacting, and finishing the mixture to the required density. The work shall be constructed in conformity with the typical sections, lines, and grades shown on the plan or as established by the Engineer, and in accordance with these specifications.
All materials shall meet the requirements of Division 10 shown below:
Lime Article 1052-3
Water Article 1024-4
Soil material shall consist of material upon which the pavement is to be placed, existing material upon which the embankment is to be placed, approved borrow material, or a combination of these materials proportioned as directed by the Engineer. The soil shall be free from vegetation, roots, or other objectionable matter, and shall not contain aggregate or stone larger than 2 inches for the full depth to be treated.
Lime stabilization shall not be performed when the air temperature is below 45 degrees F nor in the period from October 16 to March 31 except by written permission of the Engineer. The lime shall not be mixed with frozen soils or when the soils contain frost. Lime shall be applied to such areas as can be initially mixed and sealed during the day of application. Lime shall not be applied when wind conditions, as determined by the Engineer, are such that blowing lime becomes hazardous to traffic, workers, or adjacent property owners, or when excessive loss of lime may occur.
No lime treated soil shall be constructed that will not be covered with a layer of pavement or base by December 1 of that same calendar year. The Engineer may suspend the lime stabilization operations in writing when he determines that the Contractor will not cover the completed stabilization by December 1 as specified above. Failure of the Contractor to cover the lime treated soil as required above will result in the Engineer notifying the contractor in writing to cover the lime treated soil with a sand seal. The sand seal shall be applied in accordance with the requirements of Section 660 except that Articles 6603, 66011, and 66012 will not apply. This work shall be performed by the Contractor at no cost to the Department. In the event the Contractor fails to apply the sand seal within 72 hours after receipt of such notice, the Engineer may proceed to have such work performed by other forces and equipment. The cost of such work performed by other forces will be deducted from monies due or to become due to the Contractor. The application of the sand seal by the Contractor or other forces will in no way relieve the Contractor of the responsibility to maintain or repair the damaged stabilization, no matter what the cause of damage, at no cost to the Department.
(A) General:
Any combination of machines or equipment that are in good, safe working condition and that will produce the required results may be used with approval of the Engineer, except where certain types of equipment are specified in the project special provisions. Equipment necessary for the proper prosecution of the work shall be on the project and have been approved by the Engineer prior to its use in the construction operations. The machines and equipment shall be maintained in a satisfactory operating condition at all times during use. Leakage of water, oil, grease or other objectionable materials shall be corrected promptly or the Engineer may order such equipment removed from the work and replaced with satisfactory equipment. Equipment used to apply water, curing seal, and blotting sand shall be of such type and weight that it will not damage the base.
(B) Lime Spreaders:
Lime shall be spread at the required rate by methods and equipment which have been approved by the Engineer.
(C) Water Distribution Equipment:
Water shall be added to the soil with a pressure distributor or other suitable equipment capable of uniformly distributing the required amount.
(D) Mixers:
Mixing shall be done with a self-propelled rotary mixer, except that disc harrows, motor graders, and other equipment may be used only to supplement the mixing done by the rotary mixer.
All mixing equipment shall be capable of mixing to a compacted depth of at least 10 inches.
(E) Compaction Equipment:
All compaction equipment shall be self-propelled. Finish rolling shall be accomplished with a pneumatic tired roller, or as permitted by the Engineer, a smooth, steel-wheel roller, or a combination of both types.
(F) Scarifying Equipment:
A grader-scarifier, shall be used for the initial scarification of the soil. The equipment shall be capable of scarifying to the full depth of the stabilized treatment. When required by the Engineer, scarifying during finishing operations shall be done with a weeder, spiketooth harrow, or nail drag, followed by a broom drag.
Before dry lime is spread, the Contractor shall take necessary precautions and provide necessary equipment, including eye protection, dust masks, and training to protect personnel from lime dust created by the lime application and mixing operations.
Prior to the addition of any lime to the soil, the area to be stabilized shall be graded and shaped in close conformity to the typical sections, lines, and grades shown on the plans or established by the Engineer. All materials such as roots, turf, and aggregate larger than 2 inches shall be removed.
When required by the method of application, the soil shall be scarified to the required depth and width and then partially pulverized by making one pass through the area with a pulverizing rotary mixer. The pulverizing portion of the scarifying operation may be deleted in areas where, if determined by the Engineer, the soil types or conditions make pulverizing with a rotary mixer impractical.
(A) General:
When the Contractor has brought the soil layer to the elevation required by the plans or as directed by the Engineer, the Engineer will sample the soil to be stabilized in order to determine the quantity of lime to be incorporated. The Contractor shall incorporate 45 days in his schedule to allow the Engineer sufficient time to perform the required sampling, testing, and final design of the lime stabilization.
Lime or lime slurry shall be spread only on an area of such size that all primary mixing operations can be completed in the same day during daylight hours except where the work is to be done at night as required by the project special provisions or the traffic control plans.
The lime or lime slurry shall be incorporated into the soil mixture at the rates shown in the plans or as directed by the Engineer. The lime shall be distributed at the uniform rate and in such a manner as to reduce the scattering by the wind to a minimum. The lime shall be mixed into the soil within 2 hours after application.
No equipment, except that used in spreading, slaking, and mixing, will be allowed to pass over the freshly spread lime until it is mixed with the soil.
(B) Slurry Method:
Lime slurry shall not be added to the soil when the moisture content exceeds 2% above optimum moisture. Soil having a moisture content higher than 2% above optimum shall be aerated or allowed to dry naturally until it contains no more than this percentage of moisture unless otherwise directed by the Engineer. The optimum moisture will be determined by the Engineer.
Hydrated lime applied by this method shall be mixed with water in approved agitating equipment and applied to the soil to be treated as a thin water suspension or slurry. When the Contractor elects to use quicklime to produce the slurry, the slurry shall be produced by the use of equipment specifically manufactured for the slaking of quicklime. The distributing equipment shall be equipped to provide to continuous agitation of the slurry from the slurry production site until the slurry is applied to the soil. The proportion of lime shall be such that the "Dry Solids Content" shall be at least 30% by weight.
The lime application shall be split into approximately 2 equal applications with the first being partially mixed into the soil to a minimum depth of 3 inches prior to applying the second application.
(C) Quicklime:
Dry quicklime shall not be added to the soil when the moisture content exceeds 4% above optimum moisture. Soil having a moisture content higher than 4% above optimum shall be aerated or allowed to dry naturally until it contains no more than this percentage of moisture unless otherwise directed by the Engineer. The optimum moisture will be determined by the Engineer.
Where the "Bottom-Dump" method of application is used, the preliminary scarification of the soil surface shall be omitted. The quicklime will be applied by slowly driving the tanker truck over the coverage area with the bottom discharge valves open which will create a windrow of quicklime.
Repeat the process until the tanker is empty in order to provide a minimum of 3 (for 24ft. roadway) reasonably uniform and equally spaced windrows over the area being stabilized. The number of windrows required will depend on the width of the section being stabilized and will be stipulated by the Engineer.
Carefully spread the windrows of quicklime with a motor grader into an equal depth layer over the entire area to be stabilized.
After the lime has been spread, it will be followed by sprinkling to slake the lime. After a complete slaking of the lime, it will then be thoroughly mixed with the soil. The Engineer may direct that the lime first be mixed into the soil followed by sprinkling and additional mixing to insure complete slaking of the lime throughout the layer to be stabilized.
(D) Hydrated Lime:
Hydrated lime shall be used only with written permission of the Engineer and shall not be added to the soil when the moisture content exceeds 6% above optimum moisture.
(A) Primary Mixing:
Immediately after the lime has been spread (and slaked, if required), it shall be mixed into the soil for the full depth of treatment. The lime shall be mixed into the soil to provide a minimum compacted depth of 8 inches unless otherwise directed by the Engineer. A minimum number of mixing passes will be required to assure uniform incorporation of the lime. Water shall be added as necessary and thoroughly mixed with the soil lime mixture so that the mixture will contain no less than optimum. A tolerance of 3% above optimum will be allowed. All of the lime shall be thoroughly and uniformly incorporated into the soil layer to the full depth of treatment in such a manner that the result is a homogeneous, friable mixture of soil and lime, free of clods or lumps exceeding 2 inches in size.
After primary mixing operations, the lime-treated layer shall be shaped to approximate section and compacted lightly prior to curing in order to minimize evaporation loss. The surface shall be crowned as to properly drain.
(B) Preliminary Curing:
Following primary mixing operations, the stabilized layer shall be allowed to cure for 1 to 4 days. The actual duration of this curing period will be determined by the Engineer. During the curing period the surface of the material shall be kept moist to prevent drying and cracking, and maintained in a properly sealed and crowned condition as directed by the Engineer. The stabilized layer shall be mixed, compacted, shaped, and finished no later than 4 days after primary mixing.
(C) Final Mixing and Pulverizing:
Immediately after the completion of the preliminary curing period, the stabilized layer shall again be completely mixed and pulverized to the full depth of the stabilization. Final mixing shall continue until all of the clods are broken down to pass a 1/2 inch sieve and at least 80% pass a No. 4 sieve, exclusive of rock. Additional water may be required during the final mixing to raise the moisture content prior to compaction.
501-10 COMPACTING, SHAPING, AND FINISHING.
Compaction of the mixture shall begin immediately after completion of the final mixing operations. The mixture shall be aerated or moistened as necessary during compaction operations to maintain the moisture between optimum and optimum plus 2%. The full depth of the mixture shall be compacted to a density equal to at least 97% of that obtained by compacting a sample of the soil lime mixture in accordance with AASHTO T99 as modified by the Department. Copies of these modified procedures are available upon request from Materials and Tests Unit. Compaction shall be accompanied by sufficient blading to eliminate irregularities.
Final rolling of the completed surface shall be accomplished with a pneumatic- tired roller or if permitted by the Engineer, a smooth, steel wheel roller.
Upon completion of the preliminary curing, the shaping, the final mixing, compacting, and finishing shall be completed on the same day during daylight hours unless provided otherwise in the project special provisions or the traffic control plans. If the above work is not completed as directed, the entire section shall be ripped up and additional lime shall be added, if necessary, as directed by the Engineer. The additional lime shall be furnished and work performed at no cost to the Department.
The compacted thickness of the completed treated soil layer will be determined by measurements made in test holes located at random intervals not to exceed 500 feet. The measured thickness shall not deviate from that shown on the plans or established by the Engineer by more than plus 1 inch or minus 1/2 inch.
Where the lime treated soil layer is deficient in thickness by more than 1/2 inch, the area of deficient thickness shall be removed and replaced by lime treated soil having the required thickness at no cost to the Department.
As an exception to the above, if the deficiency is not considered sufficient to seriously impair the required strength of the lime treated soil layer, the deficient area may, at the discretion of the Engineer, be left in place. However, only 50% payment will be made for the lime treated soil and the theoretical amount of lime used.
After the lime treated soil has been finished in accordance with Article 50110, it shall be protected against drying for a 7 day curing period in accordance with the provisions of Section 543.
Completed sections of the lime treated soil may be opened when necessary to lightweight local traffic, provided it has hardened sufficiently to prevent marring or distorting of the surface, and provided the curing is not impaired. Construction equipment shall not use the lime treated soil except as necessary to discharge material into the spreader during paving operations, or except as may be otherwise permitted for embankment construction.
The Contractor shall maintain the lime treated soil in an acceptable condition until final acceptance of the project. Maintenance shall include immediate repair of any defects or damage that may occur. This work will be performed by the Contractor at no cost to the Department and shall be repeated as often as may be necessary to keep the lime treated soil in an acceptable condition. Repairs to lime treated soil shall be performed by replacing the lime treated soil for its full depth rather than by adding a thin layer of lime stabilized material to the existing layer. An alternate repair method may be approved in writing by the Engineer.
(A) Lime Treated Soil:
The quantity of lime treated soil to be paid for will be the number of square yards of each layer of lime treated soil which has been completed and accepted. In determining this quantity, the width of the lime treated soil will be measured across the top surface of the treated layer. The length will be the actual length constructed, measured along the centerline of the surface of the treated layer.
(B) Lime:
Where hydrated lime or quick lime is spread directly on the soil in solid form or when hydrated lime is used to produce a slurry, the quantity of lime to be paid for will be the number of tons of lime that has been incorporated into the soil at the required rates. No measurement will be made of any lime added or replaced for corrective measures during construction or for repairing damaged areas. Measurement is to be made in bulk in the truck on certified platform scales or other certified weighting devices.
Where quicklime is slaked on the project and applied in slurry form, measurement will be calculated as indicated below for each truckload using the certified lime purity for that load.
A = Certified weight of quicklime delivered x % purity x 1.32
B = Certified weight of quicklime delivered x % inert material
A+B = Total hydrated lime produced (pay quantity)
The quantity of lime treated soil, measured as provided in Subarticle 50115(A), will be paid for at the contract unit price per square yard for "Lime Treated Soil".
The quantity of lime, measured as provided in Subarticle 50115(B), will be paid for at the contract unit price per ton for "Lime for Lime Treated Soil".
Asphalt curing seal will be paid for as provided in Article 5436.
Blotting sand will be paid for as provided in Article 8185.
In the event that a layer of lime treated soil is deficient in thickness but has been permitted to be left in place in accordance with Article 50111, payment for that lime treated soil and lime will be made at 50 percent of the contract unit prices for "Lime Treated Soil" and "Lime for Lime Treated Soil".
The above prices and payments will be full compensation for all work covered by this section including but not limited to the furnishing of lime and water; preparation of the soil layer to be stabilized; the hauling, proportioning, spreading, and mixing of the materials within the depth range as shown on plans; manipulating, compacting, and finishing the lime treated soil; correcting, repairing, and maintaining the lime treated soil; and applying a sand seal in accordance with the provisions of Article 5013.
Payment will be made under:
Lime Treated Soil Square Yard
Lime for Lime Treated Soil Ton