6-24-97

LIME MODIFICATION OF SOILS 
207-R-334

DESCRIPTION: This work shall consist of upgrading fine grained soils by uniformly mixing lime, as specified, to aid compaction by drying out wet areas, and to provide a working platform for subsequent construction.

MATERIALS: Materials shall be in accordance with the following:

Hydrated lime ..........    913.04.
Water................           913.01.

 EQUIPMENT: The machinery, tools and equipment necessary for proper execution of the work shall be available on the project site and approved by the Engineer prior to the commencing of construction operations.

 STORAGE AND HANDLING: 

  1. Hydrated lime shall be stored in closed weatherproof containers until immediately before distribution on the subgrade. Hydrated lime in bags shall be stored in weather protected conditions with adequate protection from ground dampness. The storage facility shall be approved by the Engineer prior to commencement of any lime work.

  2. Each shipment shall be accompanied by a bill of lading and by a certificate of compliance stating conformance to the applicable specifications

  3. The Contractor's safety measures shall comply with applicable OSHA standards.

MIXTURE COMPOSITION: 

  1. Sample: 50 kg (110 lb), minimum, samples of the soil to be modified and 5 kg (11 lb), minimum, samples of the lime to be used shall be provided least 20 days prior to the use of the lime.

  2. Mix Design: Lime shall be proportioned as required by test results of the mixture of lime and soil on an oven - dry basis. The required proportion of lime will be established by the Engineer prior to construction, using samples of soil and lime, and the Department's laboratory design procedure for lime modified soil. The Engineer reserves the right to make such adjustments of lime proportioning as are necessary during the progress of the work within the range specified. The Engineer may add 1% to 2% extra lime if the soils and moisture content change.

    The source or type of lime shall not be changed during the progress of the work without permission of the Engineer. However, the Engineer may choose, based on laboratory test results, to use different types of lime on different portions of the project. The different types of lime shall not be mixed in the same project portions.

CONSTRUCTION REQUIREMENTS: 

  1. Temperature and Weather Limitations: Lime modification shall be performed only with a minimum soil temperature, measured 100 mm (4 in.) below the subgrade, of 7E C (45E F), and with the air temperature rising. Lime shall not be mixed with frozen soils or with soil containing frost.

  2. Preparation of Existing Roadway: All deleterious material, such as stumps, roots, turf, etc, and aggregate larger than 75 mm (3 in.) shall be removed. All soft organic soils shall be removed as directed by the Engineer.

  3. Spreading of Lime: The subgrade shall be scarified or disked prior to distribution of the lime using a machine of such design that a visible indication is given at all times that the machine is cutting to the required depth. The lime shall then be distributed uniformly over the surface by means of a cyclone, screw-type, or pressure manifold type distributor. The Engineer may reject any procedure which does not provide even distribution of lime.

  4. Mixing: The lime, soil, and water if necessary, shall be mixed by rotary speed mixers or a disc harrow. The mixing shall continue until it has been determined by the Engineer that a homogeneous layer of the specified thickness has been obtained and such that 100%, exclusive of rock particles, shall pass a 25 mm (1 in.) sieve and at least 60% will pass a 4.75 mm (No. 4) sieve. The loose thickness of a single lime modified layer shall not exceed 200 mm (8 in.) if a disc harrow is used and 360 mm (14 in.) if a rotary speed mixer is used.

  5. Compaction: Compaction of the mixture shall begin immediately after mixing. If compaction is to be delayed, the surface of the lime modified soil shall be crown-graded by either blade dragging or light rolling immediately after mixing and sealed.

    Compaction shall be continued until the lime modified layer has a density not less than 100 % of the maximum dry density within the special subgrade treatment zone or 95% of the maximum dry density below the special subgrade treatment zone. Maximum dry densities will be determined in accordance with AASHTO T 99 or one point proctors in accordance with AASHTO T 272. If required density can not be achieved in the field, a one point proctor shall be performed to verify the target density. The standard dry density of the lime treated soil shall be obtained by one point proctor in accordance with AASHTO T 272. The field in-place dry density will be obtained by the Engineer in accordance with AASHTO T 191 or T 239.

    Aeration by means of further mixing, or the addition of water and further mixing, may be required by the Engineer to achieve the required compaction.

  6. Finishing: When compaction of the lime modified soil is nearing completion, the surface shall be shaped to the required lines, grades and cross section. Compaction shall then be continued until uniform and adequate compaction is obtained.

    The average compacted thickness of modified subgrade constructed shall be within 10% of the specified thickness, except that the thickness at any one place may be within 15% of that specified.

    The Department reserves the right to determine the actual thickness of the completed and cured layer by coring, use of a phenolphthalein solution, or by other means. The Engineer will perform at least one test every 280 m2 (335 syds) for each compacted lift to insure that the lime is spread at the specified rate. All deficient areas shall be acceptably corrected

 

METHOD OF MEASUREMENT:

  1. Measured Quantities: Lime modified soils will be measured in square meters (square yards) per the depth specified. The width for measurement shall be as shown on the plans. Water will not be measured for payment.

    Lime will be measured in megagrams (tons). The lime may be weighed in trucks or freight cars. If the lime is shipped in trucks, it may be weighed at the place of loading, at the place of unloading, or where otherwise directed. The Engineer may accept original signed bills in lieu of weighing.

  2. Contract Quantities: When the project is constructed essentially to the lines, grades or dimensions shown on the plans, and the Contractor and the Engineer have agreed in writing that the plan quantities are accurate, no further measurement will be required except when errors are discovered after work has been started. Corrective measurements shall then be made.

    When the plans have been altered or when disagreement exists between the Contractor and the Engineer as to the accuracy of the plan quantities, either party shall, before any work which would affect the measurements is started, have the right to request in writing and thereby cause the quantities involved to be measured as specified herein.

    Should the Contractor's method of construction require extra earth excavation or embankment due to requiring more than one lift to construct the lime modified soil layer as shown on the plans, the extra earth excavation and embankment will not be measured.

 

BASIS OF PAYMENT: The accepted quantities of lime modified soil will be paid for at the contract unit price per square meter (square yard) for the thickness specified. Lime will be paid for at the contract unit price per megagram (ton).

 

PAYMENT WILL BE MADE UNDER     

Metric Pay Unit Symbol
(English Pay Unit Symbol)

Lime Modified Soil,_______in
             thickness

  ......................m2 (SYS)

Lime

  ......................Mg (TON)

        The costs of removal of deleterious materials, scarification of the subgrade, spreading of lime, mixing of the lime and soil, sealing of the surface of the lime modified soils, compaction of the resultant mixture, shaping the subgrade, work required due to adjustments of lime proportioning made by the Engineer, additional lime required due to weather conditions, correction of lime dust deficient areas, water required for the modification process, required extra earth excavation and embankment due to method of construction, and cost of modified subgrade trimming as required shall be included in the costs of the pay items.