02125 Full Depth Recycling.doc

Base Pavements IDIQ

JCGU 09-1700

DIVISION 02 - SITEWORK

SECTION 02125 – FULL-DEPTH RECYCLING WITH CEMENT

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 revision in effect on the date of solicitation except where a date is given.

American Society for Testing and Materials (ASTM) Publications:

C136 Sieve Analysis of Fine and Coarse Aggregates

C150 Portland Cement

D422 Particle Size Analysis of Soils

D1557 Moisture-Density Relations of Soils and Soil-Aggregate

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

D4318 Liquid Limit, Plastic Limit, and Plasticity of Soils

PORTLAND CEMENT ASSOCIATION:

Thickness Design For Soil-Cement Pavements

Soil-Cement Construction Handbook

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

1.2 DEFINITIONS:

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

1.2.2 Portland cement-stabilized base, or subbase, course, as used herein, is a mixture of Portland cement and in-place, or select borrow, material uniformly blended and thoroughly compacted to produce a pavement course which meets the criteria set forth in the drawings and specifications.

1.3 GENERAL:

1.3.1 Work shall consist of salvaging existing base and/or subbase material, after the flexible pavement structure has been broken into particles less than 1-1/2 inches in size and mixed with soil, portland cement and water as required with new Stabilized Aggregate Base Course (SABC). Method of accomplishment shall be by scarifying or a combination but shall be referred to herein as the "Full-Depth Recycling with Cement" regardless of the actual equipment used to demo the flexible pavement structure. All work shall be in accordance with TXDOT Item 275, 2004 Edition. The mix shall not include more than 50% asphalt concrete.

1.3.2 Prepare subgrade to lines and grades as described in the Task Order. Unsuitable existing soil or material shall be removed and replaced with acceptable material prior to portland cement treatment.

1.3.3 Reinstall salvaged base material and surface as described in the Task Order.

1.3.4 New SABC material shall be furnished, as directed or if the salvage mixture of base and surface does not provide specified thickness.

1.3.5 Apply cement only on an area where mixing, compacting, and finishing operations can be completed during the same work day. Do not start the cement treatment operation unless the air temperature is at least 35 deg. F and rising, or is at least 40 deg. F. The temperature shall be taken in the shade and away from artificial heat.

1.4 SUBMITTALS:

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

Mix Design: IAW TXDOT Item 275, 2004 Edition

Proposed mix design, prior to the start of stabilization work. No substitutions shall be made in the materials used in the work without additional tests to show that the quality of the concrete is satisfactory. Compressive strength shall be 1000psi at 7 days.

PART 2 – PRODUCTS:

2.1 MATERIALS: IAW TXDOT Item 275, 2004 Edition.

2.1.1 Existing base and/or bituminous surface shall be broken into particles not more than one & half inches in size, and uniformly incorporated together and salvaged.

2.1.2 Additional base material shall be furnished in accordance with Specification SECTION 02241 Stabilized Aggregate Base Course if the salvage base and surface does not provide specified thickness as described in the Task Order. Finished new base material shall meet the requirements of TXDOT Item 247.

2.1.3 Cement shall conform to C 150, Type I, and Specification SECTION 03300.

PART 3 – EXECUTION:

3.1 BASE AND SURFACE: IAW TXDOT Item 275, 2004 Edition.

3.1.1 Pulverize to full width and depth but not to exceed 8" deep.

3.1.2 Pulverize bituminous surface and base material into particles not to exceed 1-1/2 (1.5) inches in size. This salvaged mixture shall be uniform in gradation and quality, and not less than 55% nor more than 80% of the mixture shall pass the #4 sieve, taken in accordance with ASTM C 136.

3.1.3 The base and surface shall be pulverized, plowed, mixed, and blended into a uniform mixture of base and surface materials prior to being stockpiled or compacted.

3.1.4 Stockpile, or windrow as directed, the salvaged material to eliminate contamination with undesirable materials. With salvaged material removed from the underlying subgrade, subgrade shall be prepared in accordance with Specification SECTION 02225 – Earthwork and have a minimum of at least 96% standard proctor density in accordance with ASTM D 1557.

3.1.5 Salvaged material shall be mixed and blended with any new SABC added.

3.1.6 Portland cement shall be added either by a dry process or a slurry process, as defined in TXDOT. Cement shall be applied so that when uniformly mixed with the soil, the specified cement content is obtained, and a sufficient quantity of cement-treated soil is produced to construct a compacted cement-treated course conforming to the lines, grades, and cross-section as described in the Task Order. Water shall be added to the mixture to produce the optimum moisture content as determined by ASTM D 1557. Mix until a homogeneous mixture is obtained.

3.1.7 The surface shall be moistened, if necessary, and shaped to the required lines, grades, and cross-section. The surface shall then be thoroughly compacted to the specified density with rubber-tired rollers and smooth-wheel tandem rollers to the extent necessary to provide a smooth, dense, uniform surface that is free of surface checking, ridges, or loose material, and that conforms to the crown, grade, and line indicated. In places not accessible to finishing and shaping equipment, the mixtures shall be compacted with mechanical tampers to the density specified and shall be shaped and finished by hand methods. Refer to TXDOT Item 275, Edition 204 for all curing procedures with a minimum 7 day curing period. The Contractor shall not be permitted to drive heavy equipment over completed portions. The Contractor shall perform immediate repairs of any defect that may occur after cement is applied at no additional cost to the Government.

END OF SECTION

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