ITEM 203 – LIME STABILIZED ROAD MIX BASE COURSE

203.1 Description

This item shall consist of a foundation for surface course composed of soil aggregate, lime and water in proper proportions, road-mixed and constructed on a prepared subgrade/subbase in accordance with this Specification and lines, grades and typical cross-sections shown on the Plans, or established by the Engineer.

203.2 Material Requirements

203.2.1 Soil Aggregate

It shall consist of any combination of gravel, sand, silt and clay or other approved combination of materials free vegetable or other objectionable matter. It may be materials encountered in the construction site or materials obtained from approved sources. The crushed or uncrushed granular material shall consist of hard, durable stones and rocks of accepted quality, free from an excess of flat, elongated, soft or disintegrated pieces or other objectionable matter. It is the intent of this Specification to utilize soils existing on the roadbed if the quality is satisfactory. If the quality and/or quantity is deficient, the soils aggregate shall be obtained wholly or partially from approved outside sources.

The soil-aggregate shall conform to the grading requirements of table 203.1

Table 203.1 – Grading Requirements

Sieve Designation		Mass percent Passing
Standard,mm	Alternate US Standard	Grading A	Grading B
50 4.75 2.00 0.425 0.075	2" No. 4 No. 10 No. 40 No. 200	100 45 - 100 37 - 80 15 - 20 0 - 25	100 55 - 100 45 - 100 25 - 80 11 -35

        The materials passing the 4.75 mm (No. 4) sieve produces in the crushing operation of either stone or gravel shall be incorporated in the base material to the extent permitted by the gradation requirements. The plasticity index shall not be less than 4 nor more than 10.

The aggregate shall have a mass percent of wear not exceeding 50 as determined by AASHTO Method T 96.

203.2.1.1 New Soil-Aggregate

It shall conform to the applicable requirements of Subsection 203.2.1, Soil Aggregate.

203.2.1.2 Salvaged Soil-Aggregate

Where soil-aggregate required is already in place, the Contractor shall not be responsible for its grading or quality except for removal of oversized materials as directed by the Engineer. In general, salvaged soil-aggregate to be used for lime stabilized road mix base course will consist of material meeting the requirement given I Subsection 203.2.1, Soil Aggregate.

203.2.2 Hydrated Lime

It shall conform to the requirements of Item 701, Construction Lime.

203.2.3 Water

It shall conform to the requirements of Item 714, Water.

203.2.4 Proportioning of Mixture

The amount of lime to be added to the soil-aggregate shall be from 3 to 12 mass percent of the dry soil. The exact percentage to be added shall be fixed by the Engineer on the basis of preliminary laboratory tests and trial mixes of materials furnished.

203.2.5 Strength Requirement

CBR Test for Gravelly Soils. The mixture passing the 19 mm sieve shall have a minimum soaked CBR-value of 100% tested according to AASHTO T 193. The CBR-value shall be obtained at the maximum dry density determined according to AASHTO T 180, Method D.

Unconfined Compression Test for Finer Textured Soils. The 7-day compressive strength of laboratory specimen molded and compacted in accordance with ASTM D 1632 to a density of 100% maximum dry density determined according to AASHTO T 134, Method B, shall not be less than 2.1 MPa when tested in accordance with ASTM D 1633.

203.3 Construction Requirements

203.3.1 Weather Limitations

Lime shall not be applied during windy, rainy or impending bad weather. In the event rain occurs during the operations, work shall be promptly stopped and the entire section shall be reconstructed in accordance with this Specification.

203.3.2 Construction Equipment

The equipment to be used by the Contractor shall include scarifying, pulverizing. Mixing, spreading, hauling, watering, finishing and compacting equipment and a slurry lime distributor.

Distributor equipment shall include a tachometer pressure gauge, accurate volume measuring devices or a calibrated tank. It shall be equipped with a power unit for the pump and full circulation spray bars adjustable laterally and vertically, as well as agitator to prevent setting of lime solids.

These equipment shall be on the project site in good condition and shall have been approved by the Engineer, both as to type and condition, and provided with experienced operators before the start of construction.

203.3.3 Preparation of Soil-Aggregate

1. Case 1 (New Soil-Aggregate)

When new soil-aggregate is to be used, the existing roadbed shall be scarified lightly and bladed to uniform grade and to the cross-section shown on the Plans and shall then be rolled or watered and rolled, as directed. If so ordered by the Engineer, depressions shall first be filled and weak portions of the roadbed strengthened with new soil-aggregate. At least one day shall then be allowed for measuring, sampling and testing for approval of quantity and gradation before the windrow is spread for application of hydrated lime.


If the surface moisture of the soil-aggregate is more than 2 mass percent of the dry aggregate, the soil aggregate shall be turned by blades or disc harrows or otherwise aerated until the moisture content is reduced to 2 percent or less. The soil-aggregate shall then be spread smoothly ad uniformly over half the road or other convenient width of the surface ready for the application of hydrated lime. 


2. Case 2 (Salvaged Soil-Aggregate)

When material in the existing roadbed is to be used for mixing the surface shall be scarified lightly and bladed to uniform grade and to the cross-section shown on the Plans. The reshaped surface shall then be scarified again to the depth ordered by the Engineer and in such manner as to leave a foundation of undisturbed material parallel, both in profile and cross-section, the proposed finished surface. The loosened materials shall be bladed aside into a windrow at the side of the road, and the undisturbed material roiled, or watered and roiled, as directed.

203.3.4 Application of Lime

The hydrated lime shall be uniformly spread at specified percent using either the dry or slurry (wet) methods. It shall be distributed in successive applications, in such amount and at such intervals as directed. The mixing equipment shall follow immediately behind the distributor, after each application to partially mix the lime with the soil-aggregate.

Dry lime should not be spread under windy conditions to avoid excessive dustings. It shall be applied only to such areas as can be mixed into the soil-aggregate during the day of application. Dry application encompass either spotting bags of lime in equal predetermined transverse and longitudinal intervals or applying bulk lime from suitably equipped self-unloading trucks. An approved spreader is preferable for uniform distribution.

If lime slurry is employed, the preparation facilities should be approved by the Engineer. A typical slurry ratio is 1 tonne lime to 1 cubic meter water, specified type of soil and its moisture condition.

The slurry is distributed by one or more passes over a measured area until the specified percentage (based on lime solids content) is obtained. To prevent run-off and consequent non-uniformity of lime distribution, the slurry is mixed immediately after each spreading pass.

203.3.5 Mixing

After the last lime application and partial mixing, the entire mass of the mixture shall be windrowed on the road surface and then mixed by blading the mixture from side to side of the road or by manipulation producing equivalent results until the whole mass has a uniform color and the mixture id free from fat or lean spots or balls or unmixed particles. During the mixing operations, care shall be taken to avoid cutting into the underlying course. When directed, the mixing process shall be confined to part of the width or area of the road so as to allow traffic to pass.

Should the mixture show an excess, deficiency or uneven distribution of lime, the condition shall be corrected by the addition of soil-aggregate or lime as required and then remix. If the mixture contains excessive amounts of moisture or volatile matter, as may be encountered in slurry application method, it shall be bladed, aerated or otherwise manipulated until the moisture and volatile content are satisfactory. The spreading of the mix shall not be done when the surface to be covered is in an unsatisfactory condition. At the end of each day’s work, or when the work is interrupted by weather conditions or otherwise, all loose materials shall be bladed into a windrows, whether mixing is completed or not, and shall be retained in a windrow until operations are resumed.

When the mixing operations have been satisfactorily completed, the mixture shall be formed into a windrow of uniform cross-section.

203.3.6 Spearing, Compacting and Finishing

The material shall be spread by a self-propelled pneumatic-tire blade grader or a mechanical spreader of approved type. In spreading from the windrow, care shall be taken to avoid cutting into the underlying course.

After the material is spread, the surface shall be rolled. Rolling shall be parallel to the road center line and shall commence at the outer edges of the road, overlapping the shoulders and progress toward the center, overlapping on successive passes by at least one-half the width of the roller, except that o superelevated curves rolling shall progress from the lower to the upper edge. Each pass shall terminate at least 910 mm in advance or to the rear of the end of the preceding pass. During compaction, the surface shall be dragged or bladed as necessary to fill ruts and to remove incipient corrugation or other irregularities. Rolling shall continue until the surface is of uniform texture and satisfactory compaction is obtained. Initial rolling shall be performed with a pneumatic tire roller and final rolling with a 3-wheel or tandem-type steel wheel roller. Rolling shall be discontinued whenever it begins to produce excessive pulverizing of the aggregate or displacement of the mixture.

When the compacted thickness of the road mix lime stabilized base course is to be more than 150 mm, the mixture shall be spread from the windrow and compacted in two (2) approximately equal layers. The first layer shall be bladed and rolled before the second layer is spread.

Compaction shall continue until a field density of not less than 100% of the compacted maximum dry density determined in accordance with AASHTO T 180, Method D has been attained. Field Density test shall be in accordance with AASHTO T 191.

203.3.7 Protection, Curing and Maintenance

After the lime-stabilized base course has been finished as specified herein, the surface shall be protected against rapid drying for a period of at least five (5) days by either of the following curing methods:

1. Maintain in a through and continuously moist condition by sprinkling with water.


2. Cover the completed surface with a 50 mm layer of earth or sand and maintain in moist condition.


3. Apply on the surface an asphalt membrane of the type and quantity approved by the Engineer.


4. Apply on the surface a liquid membrane curing compound of the type and quantity approved by the Engineer.

The Contractor shall be required to maintain at his own expense the entire work within the limits of his Contract in good condition satisfactory to the Engineer from the time he first started work until all work shall have been completed. Maintenance shall include immediate repairs of any defects that may occur before and after the lime-stabilized base course has been compacted and finished, which work shall be done by the contractor at his own expense and repeated as may be necessary to keep the base continuously intact.

203.3.8 Trial Sections

Trial sections of the stabilized base shall be constructed at least 2 weeks before actual base construction. These shall conform to the applicable requirements of Subsection 200.3.4, Trial Sections.

203.3.9 Tolerances

The stabilized base course shall be laid to the designed level and transvers slopes shown on the Plans. The allowable tolerances shall be in accordance with Subsection 201.3.5, Tolerance.

203.3.10 Traffic

The Contractor will not be permitted to drive heavy equipment over completed portions prior to the end of five (5) days curing period except pneumatic-tired equipment required for constructing adjoining sections. Turning areas on completed portions of the base shall be protected by a layer of stable granular materials of not less than 50 mm of compacted depth.

203.4 Method of Measurement

Lime Stabilized Road Mix Base Course will be measured by the cubic meter (m3). The quantity to be paid for shall be the design volume compacted in place as shown on the Plans, and accepted in the completed course. No allowance shall be given for materials placed outside the design limits shown on the cross-sections. Trial sections shall not be measured separately but shall be included in the quantity of lime stabilized road mix base course.

203.5 Basis of Payment

The accepted quantities, measured as prescribed in Section 203.4, shall be paid for at the contract unit price for Lime Stabilized Road Mix Base Course which price and payment shall be full compensation for furnishing and placing all materials, including all labor, equipment, tools and incidentals necessary to complete the work prescribed in this Item.

Payment will be made under:

Pay  Item Number	Description	Unit of Measurement
203	Lime Stabilized Road Mix Base Course, (New or Salvaged) Soil-Aggregate	Cubic Meter