02240 Lime Stabilized Subgrade.doc

Base Pavements IDIQ

JCGU 09-1700

DIVISION 2 - SITE WORK

SECTION 02240 - LIME STABILIZED SUBGRADE

PART 1 – GENERAL:

1.1 APPLICABLE PUBLICATIONS: The publications listed below form a part of this specification to the extent referenced. The publications are referred to in the text by basic designation only. All publications shall be the latest version/edition/revision of the documents listed below, in effect on the date of this solicitation, except where a date is given.

American Society for Testing and Materials (ASTM) Publications:

C 25 Chemical Analysis of Limestone, Quicklime, and Hydrated Lime

C 50 Sampling, Inspection, Packing, and Marketing of Lime and Limestone Products

C 136 Sieve Analysis of Fine and Coarse Aggregates

D 75 Sample Aggregates

D 422 Particle-Size Analysis of Soils

D 977 Emulsified Asphalt

D 1556 Density of Soil In Place by the Sand-Cone Method

D 1557 Moisture Density Relations of Soils and Soil-Aggregate Mixtures Using 10-lb. (4.54-kg) Rammer and 18-in. (457-mm Drop)

D 2027 Cutback Asphalt (Medium Curing Type)

D 2922 Density of Soil and Soil-Aggregate In Place by Nuclear Methods (Shallow Depth)

D 3017 Moisture Content of Soil and Soil-Aggregate In Place By Nuclear Methods (Shallow Depth)

D 4318 Liquid Limit, Plastic Limit and Plasticity Index of Soils

E 11 Wire Cloth Sieves for Testing Purposes

1.2 GENERAL:

The work specified herein consists of the construction of a lime-stabilized subgrade (LSSG) course. The work shall be performed in accordance with this specification and shall conform to TXDOT Items 262 and 263.

1.3 DEFINITIONS:

1.3.1 Lime-Stabilized Subgrade (LSSG), as used herein, is a mixture of lime and in-place or select borrow material uniformly blended, wetted, and thoroughly compacted to produce a pavement course which meets all criteria as set forth in the plans and this specification.

1.3.2 DEGREE OF COMPACTION: Degree of compaction required is expressed as a percentage of the maximum density obtained by the test procedure presented in ASTM D1557, Method D, abbreviated hereinafter as percent laboratory maximum density.

1.4 WEATHER LIMITATIONS:

Lime stabilization shall not be performed during freezing temperatures. When the temperature is below 40 degrees F, lime treated areas shall be protected against freezing by a sufficient covering of straw, or by other approved methods, until the course has dried out. Any areas of completed course that are damaged by freezing, rainfall, or other weather conditions shall be brought to a satisfactory condition in conformance with this specification without additional cost to the Government. Lime shall not be applied when the atmospheric temperature is less than 40 degrees F. No lime shall be applied to soils that are frozen or contain frost, or when the underlying material is frozen. If the temperature falls below 35 degrees F, completed lime-treated areas shall be protected against any detrimental effects of freezing.

1.5 SAMPLING AND TESTING:

1.5.1 GENERAL REQUIREMENTS: Sampling and testing shall be performed by an approved commercial testing laboratory or by facilities furnished by the Contractor. No work requiring testing will be permitted until the facilities have been inspected and approved. The first inspection shall be at the expense of the Government. Cost incurred for any subsequent inspection required because of failure of the facilities to pass the first inspection will be charged to the Contractor. Tests shall be performed in sufficient numbers and at the locations and times directed to insure that materials and compaction meet specified requirements. Copies of the test results shall be furnished to the Contracting Officer within 24 hours of completion of tests.

1.5.2 RESULTS: Results shall verify that the material complies with the specification. When deficiencies are found, the initial analysis shall be repeated and the material already placed shall be retested to determine the extent of unacceptable material. All in-place unacceptable material shall be replaced.

1.5.3 SAMPLING: All aggregate samples for laboratory testing shall be taken in accordance with ASTM D 75. Samples of lime shall be taken in accordance with ASTM C 50.

1.5.4 SIEVE ANALYSIS: Before starting work, one sample of material to be stabilized shall be tested in accordance with ASTM C 136 and ASTM D 422 on sieves conforming to ASTM E 11. After the initial test, a minimum of one analysis shall be performed for each 10 tons of material placed, with a minimum of three analyses for each day's run until the course is completed.

1.5.4.1 Gradation Test of Loosened and Pulverized Soil-Lime Mixture before Compaction: Not less than three tests per 8-hour shift.

1.5.5 LIQUID LIMIT AND PLASTICITY INDEX: One liquid limit and plasticity index shall be performed for each sieve analysis. Liquid limit and plasticity index shall be in accordance with ASTM D 4318.

1.5.6 CHEMICAL ANALYSIS: Lime shall be tested for the specified chemical requirements in accordance with ASTM C 25. Three tests shall be conducted for each delivery of lime.

1.5.7 SAMPLING AND TESTING DURING CONSTRUCTION: Quality control sampling and testing during construction shall be performed as specified in paragraph "FIELD QUALITY CONTROL."

1.6 SUBMITTALS:

The following shall be submitted in accordance with Specification SECTION 01010:

Tests

Tests shall establish the dry weight of non-treated soil at optimum moisture content and shall also provide a moisture-density relationship for the lime-soil mixture. Tests shall be conducted in accordance with the standards specified in paragraph DEGREE OF COMPACTION.

Test Reports

Results of laboratory tests for quality control purposes shall be submitted to the Contracting Officer and approved prior to using the material.

Copies of field tests results shall be submitted within 24 hours after the tests are performed.

Certified copies of manufacturer's test results indicating compliance of bituminous material with applicable specified requirements.

Quality Control Results: Results of laboratory tests for quality control purposes shall be submitted to the Contracting Officer and approved prior to using the material.

1.7 STOCKPILING MATERIALS:

Select material, including approved material available from excavation and grading, shall be stockpiled in the manner and at the locations designated. Before stockpiling material, storage sites shall be cleared and sloped to drain. Materials obtained from different sources shall be stockpiled separately.

PART 2 – PRODUCTS:

2.1 MATERIALS:

2.1.1 Lime: Lime shall be a standard brand of hydrated lime conforming to the following physical and chemical requirements:

2.1.1.1 Lime shall be of such gradation that 99-1/2 percent passes a No. 20 sieve and a minimum of 85 percent passes a No. 100 sieve.

2.1.1.2 Combined calcium oxide and magnesium oxide shall be not less than 70 percent.

2.1.2 Bituminous Material: Material shall conform to one of the following:

2.1.2.1 Cutback Asphalt: ASTM D 2027, Grade MC-30 or MC-70

2.1.2.2 Emulsified Asphalt: ASTM D 977, Type SS-1 or MS-1.

2.1.3 Material to be Stabilized: Material to be stabilized shall consist of in-place material in the area, approved select material, or a combination of in place material and select material. Select material shall be free of deleterious substances such as sticks, debris, organic matter, and stones greater than 3 inches in any dimension. At least 10 percent of the material shall pass the No. 40 sieve. Plasticity index shall be greater than 12. Select material shall be obtained from grading and excavation operations and from approved private source.

2.1.4 Water: Water shall be clean, fresh, and free from injurious amounts of oil, acid, salt, alkali, organic matter, and other substances deleterious to the lime or soil-lime mixture, and shall be subject to approval.

PART 3 – EXECUTION:

3.1 GENERAL REQUIREMENTS:

The material to be stabilized shall be thoroughly pulverized. The rate of application of lime for the soil-lime mixture shall be at least 4 percent by dry weight of the soil and the optimum moisture content shall be determined from soil samples. Field moisture content shall be controlled within plus or minus 2 percent of optimum. When the stabilized course is constructed in more than one layer, the previously constructed layer shall be cleaned of loose and foreign matter by sweeping with power sweeper or power brooms except that hand brooms may be used in areas where power cleaning is not practicable. Adequate drainage shall be provided during the entire construction period to prevent water from collecting or standing on the area to be stabilized or on pulverized, mixed, or partially mixed material. Line and grade stakes shall be provided as necessary for control. Grade stakes shall be in lines parallel to the centerline of the area under construction and suitably spaced for string lining.

3.2 OPERATION OF BORROW PITS:

Borrow material shall be obtained from off site sources.

3.3 PREPARATION OF AREA TO BE STABILIZED:

The area shall be cleaned of debris. The area will be inspected for adequate compaction and shall be capable of withstanding without displacement the compaction specified for the soil-lime mixture. Debris and removed unsatisfactory in-place material shall be disposed of as specified.

3.3.1 In-Place Material to be Stabilized: The entire area shall be graded to conform to the lines, grades, and cross sections shown in the plans prior to being processed. Soft or yielding subgrade areas shall be made stable before construction is begun.

3.3.2 In-Place Material to Receive Stabilized Course: Soft, yielding areas and ruts or other irregularities in the surface shall be corrected. The material in the affected areas shall be loosened and unsatisfactory material removed. Approved select material shall be added where directed. The area shall then be shaped to line, grade, and cross section, and shall be compacted to the specified density. Subgrade shall conform to Specification SECTION 02225 - EARTHWORK.

3.3.3 Select Material: Sufficient select material shall be utilized to provide the required thickness of the soil-lime layer after compaction. When in-place mixing is to be accomplished, the soil shall be graded and shaped to the approximate section and grade shown before lime stabilization is undertaken.

3.3.4 Grade Control: Underlying material shall be excavated to sufficient depth for the required stabilized-course thickness so that the finished stabilized course with the subsequent surface course will meet the fixed grade. Finished and completed stabilized area shall conform to the lines, grades, cross section, and dimensions indicated.

3.4 INSTALLATION:

3.4.1 Mixed In-Place Method

3.4.1.1 Scarifying and Pulverizing of Soil: Prior to application of lime, the soil shall be scarified and pulverized to a depth of 6 inches. Scarification shall be carefully controlled so that the layer beneath the layer to be treated is not disturbed. Depth of pulverizing shall not exceed the depth of scarification.

3.4.1.2 Application of Lime: Pulverized material shall be shaped to approximately the cross section indicated. Lime shall be applied so that when uniformly mixed with the soil, the specified lime content is obtained, and a sufficient quantity of lime-treated soil is produced to construct a compacted lime-treated course conforming to the lines, grades, and cross section indicated. Lime shall supplied in a slurry. Distributors shall be used in applying slurry. No equipment except that used in spreading and mixing shall pass over the freshly applied lime.

3.4.1.3 Initial Mixing: Immediately after the lime has been distributed, the lime and soil shall be mixed. Initial mixing shall be sufficient to alleviate any dusting or wetting of the lime that might occur in the event of wind or rainstorms. This may be accomplished several days in advance of the final application and mixing.

3.4.1.4 Water Application and Moist Mixing: Moisture content of the mixture will be determined in preparation for final mixing. Moisture in the mixture following final mixing shall not be less than the water content determined to be optimum based on dry weight of soil and shall not exceed the optimum water content by more than 3 percentage points. Water may be added in increments as large as the equipment will permit; however, such increment of water shall be partially incorporated in the mix to avoid concentration of water near the surface. After the last increment of water has been added, mixing shall be continued until the water is uniformly distributed throughout the full depth of the mixture. Particular care shall be taken to ensure satisfactory moisture distribution along the edges of the section.

3.4.2 Edges of Stabilized Course: Approved material shall be placed along the edges of the stabilized course in such quantity as will compact to the thickness of the course being constructed, or to the thickness of each layer in a multiple-layer course, allowing at least a 1 foot width of the shoulder to be rolled and compacted simultaneously with the rolling and compacting of each layer of the stabilized course.

3.4.3 Central-Plant Method: Plant shall be capable of producing a uniform lime-treated mixture at the specified lime and moisture contents. Mixture shall be hauled to the job in trucks equipped with protective covers. Underlying course shall be thoroughly moistened and the mixture then placed on the prepared area in a uniform layer with mechanical spreaders. The layer shall be uniform in thickness and surface contour and in such quantity that the completed layer, after compaction, will conform to the required grade and cross section.

3.4.4 Traveling-Plant Method: Traveling plant shall move at a uniform rate of speed and shall accomplish thorough mixing of the materials in one pass. Water and lime shall be delivered from supply trucks or bins at a predetermined rate. Windrows of prepared soil-lime mixture shall be of sufficient size to cover a predetermined width to the indicated compacted thickness.

3.4.5 Layer Thickness: Compacted thickness of the stabilized course shall be as described in the respective Task Order. Each layer shall be 6 inches +/- 3 inches in compacted thickness.

3.4.6 Compaction: Before compaction operations are started and as a continuation of the mixing operation, the mixture shall be thoroughly loosened and pulverized to the full depth so that at least 60 percent of the soil, by dry weight, exclusive of the plus No. 4 gravel or stone, will pass a No. 4 sieve. Compaction shall be started immediately after mixing is completed. During final compaction, the surface shall be moistened, if necessary, and shaped to the required lines, grades, and cross section. Density of compacted mixture shall be at least 95 percent of laboratory maximum density. Rolling shall begin at the outside edge of the surface and proceed to the center, overlapping on successive trips at least one-half the width of the roller. Alternate trips of the roller shall be slightly different lengths. The speed of the roller at all times shall be such that displacement of the mixture does not occur. Areas inaccessible to the rollers shall be compacted with mechanical tampers, and shall be shaped and finished by hand methods.

3.4.7 Finishing: The surface of the top layer shall be finished to the grade and cross section shown. The surface shall be of uniform texture. Light blading during rolling may be necessary for the finished surface to conform to the lines, grades, and cross sections. Should the surface for any reason become rough, corrugated, uneven in texture, or traffic-marked prior to completion, such unsatisfactory portions shall be scarified, reworked, re-laid, or replaced as directed. Should any portion of the course, when laid, become water soaked for any reason, that portion shall be removed immediately, and the mix placed in a windrow and aerated until a moisture content within the limits specified is obtained, and then spread, shaped, and rolled as specified above.

3.4.8 Construction Joints: At the end of each phase of construction, a straight transverse construction joint shall be formed by cutting back into the completed work to form a true vertical face free of loose or shattered material. Material along construction joints not properly compacted shall be removed and replaced with soil-lime mixture that is mixed, moistened, and compacted as specified.

3.4.9 Curing and Protection: Immediately after the soil-lime area has been finished as specified above, the surface shall be protected against rapid drying for 7 days by one of the methods specified below.

3.4.9.1 Moist Curing: The area shall be moistened by sprinkling and shall be kept moist for the 7-day curing period.

3.4.9.2 Bituminous Material: Bituminous material shall be uniformly applied by means of a bituminous distributor within a temperature range as shown. Bituminous material shall be applied in quantities of not less than 0.1 gallon per square yard nor more than 0.25 gallon per square yard. Areas inaccessible to or missed by the distributor shall be properly treated using the manually operated hose attachment. Bituminous material shall be applied only to the top layer. At the time the bituminous material is applied, the surface of the area shall be free of loose or foreign matter and shall contain sufficient moisture to prevent excessive penetration of the bituminous material. When necessary, the area shall be sprinkled immediately before the bituminous material is applied.

Degrees F

Cutback asphalt:

MC-30

60-120

MC-70

100-180

Emulsified asphalt:

SS-1

70-160

MS-1

70-160

3.5 FIELD QUALITY CONTROL:

3.5.1 General: Results of field quality control testing shall verify that materials comply with this specification. When a material source is changed, the new material shall be tested for compliance. When deficiencies are found, the initial analysis shall be repeated and the material already placed shall be re-tested to determine the extent of unacceptable material. All in-place unacceptable material shall be replaced or repaired, as directed by the Contracting Officer, at no additional cost to the Government.

3.5.2 Thickness Control: Completed thickness of the stabilized course shall be within 1/2 inch of the thickness indicated. Where the measured thickness of the stabilized course is more than 1/2 inch deficient, such areas shall be corrected by scarifying, adding mixture of proper gradation, re-blading, and re-compacting as directed. Where the measured thickness of the stabilized course is more than 1/2 inch thicker than indicated, it shall be considered as conforming to the specified thickness requirement. Average job thickness shall be the average of all thickness measurements taken for the job, but shall be within 1/4 inch of the thickness indicated. Thickness of the stabilized course shall be measured at intervals in such a manner as to ensure one measurement for each 100 square yards of stabilized course. Measurements shall be made in 3-inch diameter test holes penetrating the stabilized course.

3.5.3 Field Density: Field in-place density shall be determined in accordance with ASTM D 1556 or ASTM D 2922. When ASTM D 2922 is used, the calibration curves shall be checked, and adjusted if necessary, using the sand cone method as described in paragraph "Calibration" of the ASTM publication. ASTM D 2922 results in a wet unit weight of soil and when using this method, ASTM D 3017 shall be used to determine the moisture content of the soil. The calibration curves furnished with the moisture gauge shall be checked along with density calibration checks as described in ASTM D 3017. If ASTM D 2922 is used, in-place densities shall be checked by ASTM D 1556 at least once per lift for each 50 square yards of stabilized material. Calibration curves and calibration tests results shall be furnished to the Contracting Officer within 24 hours of conclusion of the tests. At least one field density test shall be performed for each 100 square yards of each layer of base material.

3.6 TRAFFIC:

Completed portions of the lime-treated soil area may be opened immediately to light traffic provided the curing is not impaired. After the curing period has elapsed, completed areas may be opened to all traffic, provided the stabilized course has hardened sufficiently to prevent marring or distorting of the surface by equipment or traffic. Heavy equipment shall not be permitted on the area during the curing period. Lime and water may be hauled over the completed area with pneumatic-tired equipment if approved. Finished portions of lime-stabilized soil that are traveled on by equipment used in constructing an adjoining section shall be protected in a manner to prevent equipment from marring or damaging completed work.

3.7 MAINTENANCE:

Stabilized area shall be maintained in a satisfactory condition until the completed work is accepted. Maintenance shall include immediate repairs of any defects and shall be repeated as often as necessary to keep the area intact. Defects shall be corrected as specified herein.

3.8 DISPOSAL OF UNSATISFACTORY MATERIALS:

Removed in-place materials that are unsuitable for stabilization, material that is removed for the required correction of defective areas, waste material, and debris shall be disposed of off site.

END OF SECTION

Section 02240 – Page 9 of 9