02241 Stable Aggergate Base Cource.doc

Base Pavements IDIQ

JCGU 09-1700

DIVISION 2 - SITE WORK

SECTION 02241 - STABILIZED-AGGREGATE BASE COURSE

PART 1 – GENERAL:

1.1 REFERENCES: 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:

C29/29M Unit Weight of Aggregate

C127 Specific Density and Absorption of Course Aggregate

C128 Specific Density & Absorption of Fine Aggregate

C131 Resistance to Degradation of Small-Size Coarse Aggregate by

Abrasion & Impact in the Los Angeles Machine

C136 Sieve or Screen Analysis of Fine and Course Aggregates

D75 Sampling Aggregate

D422 Particle Size Analysis of Soils

D1556 Density of Soil In-Place by the Sand Cone Method

D1557 Moisture Density Relations of Soils and Soil Aggregate Mixtures

Using 10-Lb. (4.54-kg) Rammer and 18-In. (457-mm) Drop

D2922 Density of Soil and Soil Aggregate In-Place by Nuclear Methods

(Shallow Depth)

D3017 Moisture Content of Soil and Soil Aggregate In Place by Nuclear Methods (Shallow Depth)

D4318 Liquid Limit, Plastic Limit, and Plasticity of Soils

E11 Wire Cloth Sieves for Testing Purposes

Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges, Texas Department of Transportation, June 2004.

1.2 DEFINITIONS:

1.2.1 Stabilized Aggregate Base: Stabilized Aggregate Base as used herein is well graded, durable aggregate uniformly moistened and mechanically stabilized by compaction.

1.2.2 Degree of Compaction: Degree of compaction require is expressed as a percentage of the maximum density obtained by the test procedure presented in ASTM D 1557, Method D, abbreviated hereinafter as percent laboratory maximum density.

1.3 GENERAL:

The work specified herein consists of the construction of a stabilized aggregate base course. The work shall be performed in accordance with this specification and shall conform to the lines, grades, notes and typical sections shown in the plans.

1.4 SUBMITTALS:

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

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 test results shall be submitted within 24 hours of the tests being performed.

Calibration curves and related test results shall be submitted prior to using the device or equipment being calibrated.

Sources of all materials shall be selected well in advance of the time that materials shall be required in the work. Test results from samples shall be submitted for approval not less than 5 working days before material is required for the work.

Records:

Only one type of course aggregate shall be used on the project and a notification stating which aggregate is to be used shall be submitted. Copies of waybills or delivery tickets shall be submitted during the progress of the work. Before the final payment is allowed, waybills and certified delivery tickets shall be furnished for all aggregates actually used in the construction.

1.5 WEATHER LIMITATIONS:

Base shall not be constructed when the atmospheric temperature is less than 35 degrees Fahrenheit. Base shall not be constructed on subgrades that are frozen or contain frost. If the temperature falls below 35 degrees Fahrenheit, completed areas shall be protected against any detrimental effects of freezing.

1.6 STOCKPILING MATERIALS:

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

1.7 SAMPLING AND TESTING:

1.7.1 General Requirements: The first and any subsequent inspections required because of failure of the facilities to pass the first inspection shall 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 test results shall be furnished to the Contracting Officer within 24 hours of completion of tests.

1.7.2 Test Results: Results 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 retested to determine the extent of unacceptable material. All in-place unacceptable material shall be replaced or modified as directed by the Contracting Officer.

1.7.3 Sampling: Aggregate samples for laboratory tests shall be taken in accordance with ASTM D75.

1.7.4 Sieve Analysis: Before starting work, at least one sample of material to be stabilized shall be tested in accordance with ASTM C136 and ASTM D422 on sieves conforming to ASTM E11. After the initial test, a minimum of one analysis shall be performed for each 10 tons of material placed, with a minimum of three analysis for each day's run until the course is completed.

1.7.5 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 D4318.

1.7.6 Laboratory Density: Tests shall provide a moisture-density relationship for the stabilized-aggregate. Tests shall be conducted in accordance with ASTM D1557, Method D.

1.7.7 Weight Per Cubic Foot of Slag: Weight per cubic foot of slag shall be determined in accordance with ASTM C29.

1.7.8 Wear Tests: Wear test shall be made in conformance with ASTM C131. One test shall be run per 500 square yards/or a minimum of one test per Task Order of completed base course. A minimum of one test per aggregate source shall be run.

1.7.9 Sampling and Testing during Construction: Quality control sampling and testing during construction shall be performed as specified in paragraph 3.4 - FIELD QUALITY CONTROL.

PART 2 – PRODUCTS;

2.1 MATERIALS:

2.1.1 Aggregates: Aggregates shall consist of crushed stone or slag, crushed gravel, angular sand or other approved materials. Aggregates shall be durable and sound, free lumps of clay, organic matter, objectionable coatings, and other foreign material. Aggregates shall meet the physical requirements for flexible base materials indicated in Item 248 type A, grade 1 of the TXDOT specification unless modified herein. Contractor shall be responsible for obtaining materials that meet the requirements specified herein and that can be constructed to meet the grade and smoothness requirements specified herein after all compaction requirements have been met. Material retained on a No 4 sieve shall be known as coarse aggregate and that passing the No 4 sieve shall be known as binder material.

2.1.1.1 Coarse Aggregate: Coarse aggregates, consisting of angular fragments of uniform density and quality, shall have a percentage of wear not to exceed 50 percent after 500 revolutions when tested in accordance with ASTM C131. The amount of flat and elongated particles shall not exceed 30 percent. A flat particle is one having a ratio of width to thickness greater than 3, and an elongated particle is one having a ratio of length to width greater than 3.

2.1.1.1.1 Crushed Gravel: Crushed gravel shall be manufactured from gravel particles 50 percent of which by weight are retained on the maximum size gradation sieve specified.

2.1.1.1.2 Crushed Stone: Crushed stone retained on each sieve specified shall contain at least 50 percent by weight of crushed pieces having two or more freshly fractured faces with the area of each face being at least equal to 75 percent of the smallest cross-sectional area of the piece. When two fractures are adjacent, the angle between the planes of the fractured faces.

2.1.1.2 Slag: Slag shall be an air-cooled blast-furnace product having a dry unit weight of not less than 65 pcf. Binder material shall consist of screenings, angular sand, or other finely divided mineral matter processed or naturally combined with the coarse aggregate. Liquid-limit and plasticity-index requirements shall apply to any component that is blended to meet the required gradation and shall also apply to the completed course. The portion of any component or of the completed course passing the No. 40 sieve shall be either nonplastic or have a liquid limit not greater than 35 and a plasticity index not greater than 10.

2.1.2 Gradation: Requirements for gradation specified shall apply to the completed base course. The aggregates shall have a 1 inch maximum size and shall be continuously graded within the following limits:

Percentage by Weight Retained

Sieve Designation Square-mesh Sieve

1-3/4"

7/8 10 - 35

3/8 30 - 50

No. 4 45 - 65

No. 40 70 - 85

2.1.3 The table above is based on aggregates of uniform specific gravity and the percentages passing the various sieves are subject to appropriate corrections in accordance with ASTM C 127 and C 128 when aggregates of varying specific gravity are used. The gradation above conforms to Texas Highway Department Standard Specification for base course, Item 247, Type A, Grade 1.

2.1.3.1 Particles: Particles having diameters less than 0.02 millimeter shall not be in excess of 3 percent by weight of the total sample tested.

2.1.3.2 Specific Gravity: The values are based on aggregates of uniform specific gravity, and the percentages passing the various sieves are subject to appropriate correction in accordance with ASTM C127 and ASTM C128 when aggregates of varying specific gravities are used.

PART 3 – EXECUTION:

3.1 GENERAL REQUIREMENTS:

When the base is constructed in more that one layer, the previously constructed layer shall be cleaned of loose and foreign matter by sweeping with power sweepers 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 period of construction to prevent water from collecting or standing on the area to receive the prime coat. 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 PREPARATION OF UNDERLYING COURSE:

3.2.1 General Requirements: Before constructing stabilized aggregate base course, the previously constructed underlying subgrade shall be cleaned of foreign substances. Surface of underlying course shall meet the specified compaction and surface tolerances, and shall not contain any frozen material at the time of construction. Subgrade preparation shall conform to Specification SECTIONS 02225 and/or 02240. Ruts or soft, yielding spots that may appear in the underlying course, areas having inadequate compaction, and deviations of the surface from requirements of the surface from requirements specified shall be corrected by the Contractor. For cohesionless underlying materials containing sands, sand gravels, or any other cohesionless materials in harmful quantities, the surface shall be stabilized with aggregate prior to placement of the base course. Stabilization may be accomplished by mixing base-course material into the subgrade and compacting by approved methods. Stabilized material will be considered as part of the subgrade and shall meet all requirements for the subgrade. Finished subgrade shall not be disturbed by traffic or other operations and shall be maintained in a satisfactory condition until base course is placed.

3.2.2 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 shall meet the fixed grade. Finished and completed stabilized area shall conform to the lines, grades, cross section, and dimensions indicated.

3.3 INSTALLATION:

3.3.1 Mixing and Placing: Materials shall be mixed by the stationary plant or in a traveling plant and placed in such a manner as to obtain uniformity of the stabilized aggregate base course material and at a uniform optimum water content for compaction. The Contractor shall make such adjustments in mixing or placing procedures or in equipment to obtain the true grades, to minimize segregation and degradation, to reduce or accelerate loss or increase of water, and to insure a satisfactory base course.

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

3.3.3 Compaction: Each layer of stabilized aggregate base course, including shoulder, shall be compacted with approved equipment until the layer is compacted through the full depth to at least 100 percent of CE 55 maximum density. Water content shall be maintained at optimum. Density of compacted mixture shall be at least 100 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. Speed of the roller shall be such that displacement of the aggregate does not occur (Pneumatic tired rollers shall not exceed 5 mph). Areas inaccessible to the rollers shall be compacted with mechanical tampers, and shall be shaped and finished by hand methods.

3.3.4 Layer Thickness: Compacted thickness of the base course shall be as indicated. No layer shall be in excess of 6 inches nor less than 3 inches in compacted thickness.

3.3.5 Finishing: The surface of the top layer shall be finished to grade and cross section shown after final compaction by cutting any overbuild to grade and rolling with a steel wheeled roller. Finished surface shall be of uniform texture. Light blading during compaction may be necessary for the finished surface to conformed to the lines, grades, and cross sections. In no case shall the addition of thin layers of material be added to the top layer of base course in order to meet grade. Should the surface for any reason become rough, corrugated, uneven in texture, or traffic marked prior to completion, such unsatisfactory portion shall be scarified, reworked, recompacted, or replaced as directed.

3.3.5.1 Smoothness: Surface of each layer shall show no deviations in excess of 1/4 inch when tested with the 12 foot straightedge applied parallel with and at right angles to the centerline of the paved area. Deviations exceeding this amount shall be corrected by removing material and replacing with new material, or by reworking existing material and compacting, as directed.

3.3.5.2 Thickness Control: Compacted thickness of the stabilized base course shall be within 1/2 inch of the thickness indicated. The thickness of the base course shall be measured providing at least one depth measurement for at least 500 square yards/or a minimum of one per Task Order of base course. The thickness measurement shall be made by test holes at least 3 inches in diameter through the course. Where the measured thickness is more than 1/2 inch deficient, such areas shall be corrected by scarifying, adding new material of proper gradation, reblading, and recompacting as directed. Where the measured thickness is more than 1/2 inch indicated, the course shall be considered as conforming to the specified thickness requirements. The Contractor shall make test holes and measurements shall be performed in the presence of the Contracting Officer or his designated representative.

3.4 FIELD QUALITY CONTROL:

3.4.1 Field Density: Field in-place density shall be determined in accordance with ASTM D2922. 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 gauges 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 500 square yards/or a minimum of one per Task Order of stabilized material. Calibration curves and calibration tests results shall be furnished within 24 hours of the conclusion of the tests. At least one field density test shall be performed for each 250 square yards/or a minimum of one per Task Order of each layer of base material.

3.4.2 Smoothness: Measurements for deviation from grade and cross section shown shall be taken in successive positions parallel to the road center line with a 12 foot straightedge. Measurements shall also be taken perpendicular to the road center line at 15 foot intervals.

3.4.3 Thickness: Thickness of the stabilized course shall be measured at intervals in such a manner as to ensure one measurement for each 500 square yards/or a minimum of one per Task Order of stabilized course. Measurements shall be made in 3-inch diameter test holes penetrating the stabilized course.

3.5 MAINTENANCE:

The stabilized aggregate base course shall be maintained in a satisfactory condition until accepted. Maintenance shall include immediate repairs to any defects and shall be repeated as often as necessary to keep the area intact.

3.6 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 in accordance with all applicable Federal, State, and Local regulations. The government reserves the right to retain all material.

END OF SECTION

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