ITEM 206  LIME STABILIZED SUBGRADE

206.01   Description
206.02   Materials
206.03   Limitations, Test Rolling, and Spreading
206.04   Mixing
206.05   Compacting
206.06   Contractor Designed Lime Subgrade
206.07   Method of Measurement
206.08   Basis of Payment

206.01  Description.  This work consists of constructing a lime stabilized subgrade and designing the lime percentage in the soil.  Drain and maintain the work according to 203.04.A.

206.02  Materials.  Furnish materials conforming to the requirements of 205.02, except use soil conforming to Item 204.  Furnish 408 prime coat at a rate of 0.3 gallon per square yard (1.3 L/m²) for curing.

206.03  Limitations, Test Rolling, and Spreading.  Conform to the limitations specified in 205.03.

Before adding the lime, test roll the subgrade areas designated for lime stabilization with a grader weighing at least 15 tons (14 metric tons).  The Engineer will consider areas lacking sufficient stability as soft subgrade.  The Engineer will determine the stability according to Item 204 and the current version of the Department’s Earthwork Construction Manual.  Shape the subgrade to the profile grade and typical sections to allow for the construction of a uniformly compacted course of lime stabilized subgrade to the thickness shown on the plans.

Spread the lime over the prepared subgrade according to 205.04.

206.04  Mixing.  For slurry methods, open the soil with a spring tooth or disc harrow prior to spreading.  Immediately after spreading the lime, mix the soil and lime.  Mix the lime and soil by using an approved power driven rotary type mixer.  If necessary, add water to bring the mixed material to optimum moisture content for hydrated lime and to +3 percent of optimum for quick lime.  Continue mixing until the lime is thoroughly incorporated into the soil, all soil clods are reduced to a maximum size of 2 inches (50 mm), and the mixture is a uniform color.

Following the initial mixing, lightly compact the material to seal it against rain or excessive drying using a steel wheel or pneumatic tire roller.  Before final mixing, cure the initially-mixed, lightly-compacted material for a period of not less than 24 hours and not more than 7 days.  Perform the initial cure with water.  If conditions during construction are such that more than 7 days elapse between initial mixing and final mixing, add an additional 0.5 percent of lime during the final mixing.  The Contractor shall furnish the additional lime at no cost to the Department unless the delay beyond the 7-day limit is caused by conditions beyond the Contractor’s control.

Perform the final mixing using approved power-driven rotary-type equipment until the soil is completely pulverized with all clods reduced to a maximum size of 1 inch (25 mm) and at least 60 percent of the clods passing the No. 4 (4.75 mm) sieve.  Continue mixing until the lime is uniformly distributed throughout the pulverized soil.

During final mixing, return the mixture to the moisture contents stated above, then shape and compact the mixture.

206.05  Compacting.  The Engineer will perform the compaction testing according to Supplement 1015.  Compact all lime stabilized subgrade to the requirements in 204.03, except the Engineer will use 98 percent of the maximum dry density for acceptance.  Perform the final rolling using a steel wheel roller with a minimum weight or centrifugal force of 10 tons (9 metric tons).  Shape the compacted lime stabilized subgrade to plan profile grade and typical sections within subgrade tolerances specified in 204.06 and 203.08.  When fine grading is needed, perform the fine grading and re-compact the subgrade before curing.

Immediately following the grading or fine grading, cure the compacted lime stabilized subgrade for a period of at least 5 days before placing the overlying course.  Protect and do not operate construction equipment on the lime stabilized subgrade during the cure period.  Cover the surface with Item 408 prime coat for curing the lime stabilized subgrade.

206.06  Contractor Designed Lime Subgrade.  If specified in the Contract Documents, design the percent of lime in the soil according to 205.07.

206.07  Method of Measurement.  The Department will measure of Lime Stabilized Subgrade (dry or slurry method) by the number of square yards (square meters) computed from the profile grade and typical sections accepted in place.

The Department will measure Lime by the number of tons (metric tons) incorporated in the complete and accepted work.  The Department will measure the quality according to 205.08.

The Department will measure Water by the number of M gallons (cubic meters) applied in the complete and accepted work, as determined by Item 616.  The Department will measure the quality according to 205.09.

The Department will measure Test Rolling according to 204.08 as specified for Proof Rolling.

The Department will not measure Contractor Designed Lime Subgrade.

206.08 Basis of Payment.  The Department will pay for prime coat used for curing under Item 408.  The Department will not pay for water used for initial cure as required in 206.04.

The Department will pay for water to make the slurry, when the slurry method is specified.

The Department will pay for Contractor Designed Lime Subgrade as specified in 205.08.

The Department will pay for accepted quantities at the contract prices as follows: