02511 Concrete Sidewalks.doc

Base Pavements IDIQ

JCGU 09-1700

DIVISION 02 - SITEWORK

SECTION 02511 - CONCRETE, SIDEWALKS,

TROOPWALKS, CURBS AND GUTTERS

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 Concrete Institute (ACI)

ACI 318/318R Building Code Requirements for Structural Concrete and Commentary

American Association of State Highway and Transportation Officials (AASHTO)

AASHTO M 182

Burlap Cloth made from Jute or Kenef

American Society for Testing and Materials (ASTM)

ASTM A 185

Steel Welded Wire, Fabric, Plain, for Concrete Reinforcement

ASTM A 615

Deformed and Plain Billet-Steel Bars for Concrete Reinforcement

ASTM A 706

Low-Alloy Steel Deformed Bars for Concrete Reinforcement

ASTM C 31

Making and Curing Concrete Test Specimens in the Field

ASTM C 94

Ready-Mixed Concrete

ASTM C 143

Slump of Portland Cement Concrete

ASTM C 171

Sheet Materials for Curing Concrete

ASTM C 172

Sampling Freshly Mixed Concrete

ASTM C 173

Air Content of Freshly Mixed Concrete by the Volumetric Method

ASTM C 231

Air Content of Freshly Mixed Concrete by the Pressure Method

ASTM C 270

Mortar of Unit Masonry

ASTM C 309

Liquid Membrane-Forming Compounds for Curing Concrete

ASTM C 1116

Fiber-Reinforced Concrete and Shotcrete

ASTM D 1190

Concrete Joint Sealer, Cold-Application type

ASTM D 1751

Preformed Expansion Joint Filler for Concrete Paving and

Structural Construction (Nonextruding and Resilient

Bituminous Types)

ASTM D 1850

Concrete Joint Sealer, Cold Application Type

FEDERAL SPECIFICATIONS (Fed Spec)

FS SS-S-1401

Sealant, Joint, Non-Jet-Fuel-Resistant Hot-Applied, for Portland Cement and Asphalt Concrete Pavements

1.2 FIELD CONTROL TESTS:

Preparation of field-control samples and testing of samples shall be by the Contractor. Three cylinders per day's pour shall be prepared for testing by certified soils testing laboratory and 4 copies of the test results shall be furnished to the Contracting Officer.

1.3 SUBMITTALS:

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

Test Reports:

Copies of all test reports for tests specified in paragraphs "Concrete" and "Field Quality Control" shall be submitted within 24 hours of the completion of the test.

Records:

Copies of certified delivery tickets for all concrete used in Task Order(s).

Materials: Data on Fibermesh Reinforcement and Brick Pavers

Certification of compliance/catalog data for materials listed in paragraphs 2.1.2.1, 2.3, 2.5, and 2.7.

Concrete mix design and concrete testing as described above.

1.4 WEATHER LIMITATIONS:

1.4.1 Placing During Cold Weather: Concrete placement shall be discontinued when the air temperature reaches 40 degrees F and is falling. Placement may begin when the air temperature reaches 35 degrees F and is rising. Provisions shall be made to protect the concrete from freezing during the specified curing period. If necessary to place concrete when the temperature of the air, aggregates, or water is below 35 degrees F, placement shall be approved in writing. Approval shall be contingent upon full conformance with the following provisions. The underlying material shall be prepared and protected so that it is entirely free of frost when the concrete is deposited. Mixing water and aggregates shall be heated as necessary to result in the temperature of the in-place concrete being between 50 and 85 degrees F. Methods and equipment for heating shall be approved. The aggregates shall be free of ice, snow, and frozen lumps before entering the mixer. Covering and other means shall be provided for maintaining the concrete at a temperature of at least 50 degrees F for not less than 72 hours after placing, and at a temperature above freezing for the remainder of the curing period.

1.4.2 Placing During Warm Weather: The temperature of the concrete as placed shall not exceed 85 degrees F except where an approved retarder is used. The mixing water and/or aggregates shall be cooled, if necessary, to maintain a satisfactory placing temperature. In no case shall the placing temperature exceed 95 degrees F.

PART 2 – PRODUCTS:

2.1 PORTLAND CEMENT CONCRETE (PCC): Concrete (PCC) and the equipment, workmanship, and materials shall conform to all applicable requirements of ASTM C94, except as specified below. Concrete shall have a minimum compressive strength of 3000 psi at 28 days. The maximum size of aggregate shall be 1-1/2 inches, unless otherwise noted. Concrete shall contain five (5) sacks of cement per cubic yard of mix. Concrete shall contain Pozzolith 300-N or equal at a rate of five (5) onces per 100 pounds of cement in mix. Use of accelerating admixtures in cold weather or self retarding admixtures in hot weather must be approved by the Contracting Officer.

2.1.1 Troopwalks, Curbs and Curb with Gutter: Concrete shall have a minimum compressive strength of 3000 psi at 28 days. The maximum size of aggregate shall be 1-1/2 inches.

2.1.2 Sidewalk: Concrete (fibermesh) materials shall conform to applicable requirements of ASTM C94, Alternative No. 2, except as specified below. Concrete shall have a minimum compressive strength of 3000 psi. Conform to ASTM A 615. No wire mesh reinforcement shall be used with the synthetic fiber reinforced concrete sidewalks.

The maximum size of aggregate shall be 3/4 inches.

2.1.2.1 Synthetic Fibers for Reinforcing (fibermesh): Synthetic fibers shall conform to ASTM C1116, Type III, Synthetic Fiber, and as follows. Fibers shall be 100% virgin polypropylene fibrillated fibers containing no reprocessed olefin materials. Fibers shall have a specific gravity of 0.9, a minimum tensile strength of 70 ksi graded per manufacturer, and specifically manufactured to an optimum gradation for use as concrete secondary reinforcement.

2.1.2.2 All concrete curb and gutter, and troopwalks shall have steel reinforcement. Sidewalks shall have fibermesh reinforcement.

2.2 GENERAL CONCRETE REQUIREMENTS:

2.2.1 Air Content: Mixtures shall have air content by volume of concrete of 4-1/2 percent, plus or minus 1/2 percent, based on measurements made immediately after discharge from the mixer. Air content shall be determined in accordance with ASTM C173.

2.2.2 Slump: The concrete slump shall be from 3 to 5 inches where determined in accordance with ASTM C 143.

2.2.3 Reinforcement Steel: Wire mesh reinforcement shall conform to ASTM A 185, or deformed bars conforming to ASTM A 615 or ASTM A 706 Grades & Sizes indicated. No wire mesh reinforcement is used with the synthetic fiber reinforced concrete sidewalks.

2.3 CONCRETE CURING MATERIALS:

2.3.1 Impervious Sheet Materials: Impervious sheet materials shall conform to ASTM C 171, type optional, except that polyethylene film, if used, shall be white opaque.

2.3.2 Burlap: Burlap shall conform to AASHTO M182.

2.3.3 White Pigmented Membrane-Forming Curing Compound: White pigmented membrane-forming curing compound shall conform to ASTM C 309, Type 2.

2.4 JOINT FILLER STRIPS:

2.4.1 Contraction Joint Filler for Curb and Gutter: Contraction joint filler for curb and gutter shall consist of hard-pressed fiberboard.

2.4.2 Expansion Joint Filler, Premolded: Expansion joint filler, premolded, shall conform to ASTM D 1751, 3/8-inch thick, unless otherwise indicated. Expansion Joint Filler, Premolded: Expansion joint filler, premolded, shall conform to ASTM D 1751, 3/8-inch thick, unless otherwise indicated.

2.4.3 Troopwalk Expansion Joint: A commercial red wood board made expressly for concrete joints shall be used. Clear silicone caulking shall be used to seal joints.

2.5 JOINT SEALANTS:

Joint Sealants, shall be FS SS-S-1401 at all junctures of PCC and asphalt, and ASTM D1850 at all other joints.

2.6 FORM WORK:

Form work shall be designed and constructed to insure that the finished concrete will conform accurately to the indicated dimensions, lines, and elevations, and within the tolerances specified. Forms shall be of wood or steel, straight, of sufficient strength to resist springing during depositing and consolidating concrete. Wood forms shall be surfaced plank, 2-inch nominal thickness, straight and free from warp, twist, loose knots, splits or other defects. Wood forms shall have a nominal length of 10 feet. Radius bends may be formed with 3/4-inch boards, laminated to the required thickness. Steel forms shall be channel-formed sections with a flat top surface and with welded braces at each end and at not less than two intermediate points. Ends of steel forms shall be interlocking and self-aligning. Steel forms shall include flexible forms for radius forming, corner forms, form spreaders, and fillers. Steel forms shall have a nominal length of 10 feet with a minimum of two welded stake pockets per form. Stake pins shall be solid steel rods with chamfered heads and pointed tips designed for use with steel forms.

2.6.1 Sidewalk Forms: Sidewalk forms shall be of a height equal to the full depth of the finished sidewalk.

2.6.2 Curb and Gutter Forms: Curb and gutter outside forms shall have a height equal to the full depth of the curb or gutter. The inside form of curb shall have batten as indicated and shall be securely fastened to and supported by the outside form. Rigid forms shall be provided for curb returns, except that benders or thin plank forms may be used for curb or curb returns with a radius of 10 feet or more, where grade changes occur in the return, or where the central angle is such that a rigid form with a central angle of 90 degrees cannot be used. Back forms for curb returns may be made of 1-1/2 inch benders, for the full height of the curb, cleated together.

2.7 BRICK PAVERS:

Brick pavers and mortar shall match those of existing troopwalks on Goodfellow AFB. Acme (Eureka) #260 solid modular brick or approved equal. Brick mortar shall conform to ASTM C270 with 1800 psi compressive strength with an average 28 day compressive strength of 1800 psi. Mortar not used or that has started to set within 2 ½ hours after mixing shall be discarded.

PART 3 - EXECUTION

3.1 SUBGRADE AND BASE COURSE PREPARATION:

Concrete Pavement Subgrade and Base Course: Stabilized aggregate base course shall be compacted to at least 95 percent of maximum density with a vibrating compactor or equivalent device, unless otherwise noted.

Curb and Gutter Subgrade and Base Course Preparation: The subgrade shall be constructed to the specified grade and cross section prior to concrete placement. Subgrade and base shall be placed, compacted to at least 95 percent of maximum density with a vibrating compactor or equivalent device and tested to conform with ASTM D 1556. Adjoining transitional areas shall be backfilled with topsoil and compacted to that of the surrounding soil. Subgrade and base shall be tested for grade and cross section by means of a template extending the full width of the curb and gutter.

3.1.1 Sidewalk Subgrade: The subgrade shall be thoroughly wetted and then compacted with two passes of a 500-pound roller. Yield material deflecting more than 1/2 inch under the roller shall be removed to a depth of not less than 4 inches and replaced with an approved granular material. The material shall be compacted to 80 percent of maximum density. The subgrade shall be tested for grade and cross section with a template extending the full width of the sidewalk and supported between side forms.

3.1.2 Troopwalk Subgrade and Base Course: The subgrade shall be thoroughly wetted and then compacted with two passes of a 500-pound roller. Yield material deflecting more than 1/2 inch under the roller shall be removed to a depth of not less than 4 inches and replaced with an approved granular material. The material shall then be compacted as specified above. The subgrade shall be tested for grade and cross section with a template extending the full width of the sidewalk and supported between side forms. The base course shall consist of 4” thick lime stabilized subgrade in accordance with Section 02240.

3.1.3 Maintenance of Subgrade: The subgrade shall be maintained in a smooth, compacted condition in conformity with the required section and established grade until the concrete is placed. The subgrade shall be in a moist condition when concrete is placed. The subgrade shall be prepared and protected so as to produce a subgrade free from frost when the concrete is deposited.

3.2 FORM SETTING:

Forms shall be carefully set to the indicated alignment, grade and dimensions. Forms shall be held rigidly in place by a minimum of three stakes per form placed at intervals not to exceed 4 feet. Corners, deep sections, and radius bends shall have additional stakes and braces, as required. Clamps, spreaders, and braces shall be used where required to insure rigidity in the forms. Forms shall be removed without injuring the concrete. Bars or heavy tools shall not be used against the concrete in removing the forms. Any concrete found defective after form removal shall be promptly and satisfactorily repaired. Forms shall be cleaned and coated with form oil each time before concrete is placed. Wood forms may, instead, be thoroughly wetted with water before concrete is placed, except that with probable freezing temperatures, oiling is mandatory.

3.2.1 Sidewalks and Troopwalks: Forms for sidewalks/troopwalks shall be set with the upper edge true to line and grade with an allowable tolerance of 118 inch in any 10-foot long section. After forms are set, grade and alignment shall be checked with a 10-foot straightedge. Forms shall have a transverse slope of 1/4-inch per foot with the low side adjacent to the roadway. Side forms shall not be removed for 12 hours after finishing has been completed.

3.2.2 Curbs and Gutters: The forms of the front of the curb shall be removed not less than 2 hours nor more than 6 hours after the concrete has been placed. Forms back of curb shall remain in place until the face and top of the curb have been finished as specified for concrete finishing. Gutter forms shall not be removed while the concrete is sufficiently plastic to slump in any direction.

3.3 SIDEWALK/TROOPWALK CONCRETE PLACEMENT AND FINISHING:

3.3.1 Formed Sidewalks: Concrete shall be placed in the forms in one layer of such thickness that when consolidated and finished the sidewalks will be of the thickness indicated. After concrete has been placed in the forms, a strike-off guided by side forms shall be used to bring the surface to proper section to be compacted. The concrete shall be consolidated with an approved vibrator, and the surface shall be finished to grade with a wood float, bull float, or darby, edged and broom finished.

3.3.2 Concrete Finishing: After straightedging, when most of the water sheen has disappeared, and just before the concrete hardens, the surface shall be finished to a smooth and uniformly fine granular or sandy texture free of waves, irregularities, or tool marks. A scored surface shall be produced by brooming with a fiber-bristle brush in a direction transverse to that of the traffic for sidewalks. Troopwalks shall have an exposed aggregate finish per Section 03330.

3.3.3 Edge and Joint Finishing: All slab edges, including those at formed joints, shall be finished carefully with an edger having a radius of 1/8 inch. Transverse joint shall be edged before brooming, and the brooming shall eliminate the flat surface left by the surface face of the edger. Corners and edges which have crumbled and areas which lack sufficient mortar for proper finishing shall be cleaned and filled solidly with a properly proportioned mortar mixture and then finished.

3.3.4 Contraction Joints: Contraction joints shall be constructed to divide the surface into rectangular areas. The contraction joints shall be formed in the fresh concrete by cutting a groove in the top portion of the slab to a depth of at least one quarter of the slab thickness, using a jointer to cut the groove, or by sawing a groove in the hardened concrete with a power-driven saw. Sawed joints shall be constructed by sawing a groove in the concrete with a 1/8 inch blade of the depth indicated. The time of sawing shall be varied, depending on existing and anticipated weather conditions, and shall be such as to prevent uncontrolled cracking of the concrete. Sawing of the joints shall commence as soon as the concrete has hardened sufficiently to permit cutting the concrete without chipping, spalling, or tearing. The sawed faces of the joints shall be inspected for undercutting or washing of the concrete due to early sawing and sawing shall be delayed if undercutting or washing is sufficiently deep to cause structural weakness or excessive roughness in the joint. The sawing operation shall be carried on as required during both day and night regardless of weather conditions. The joints shall be sawed at the required spacing consecutively in the sequence of the concrete placement. A chalk line or other suitable guide shall be used to mark the alignment of the joint. Contraction joints shall be constructed directly opposite contraction joints in abutting Portland cement concrete pavements and spaced so that monolithic sections between curb returns shall not be less than 5 feet nor greater than 15 feet in length. Contraction joints shall be constructed by means of 1/8-inch thick separators and of a section conforming to the cross section of the curb and gutter. Separators shall be removed as soon as practicable after concrete has set sufficiently to preserve the width and shape of the Joint and prior to finishing.

The saw cut shall not vary more than 1/2 inch from the true joint alignment. Before sawing a joint, the concrete shall be examined closely for cracks and the joint shall not be sawed if a crack has occurred near the joint location. Sawing shall be discontinued when a crack develops ahead of the saw cut. Workmen and inspectors shall wear clean, rubber soled foot wear and the number of persons walking on the concrete shall be limited to those actually performing the sawing operation. Immediately after each joint is sawed, the saw cut and adjacent concrete shall be thoroughly flushed with water until all waste from sawing is removed from the joint. Any membrane cured surface damaged during the sawing operations shall be re-sprayed as soon as the surface dries. The sawing equipment shall be adequate in number of units and power to complete the sawing at the required rate. An ample supply of saw blades shall be available on the job before concrete placement is started, and at least one standby sawing unit in good working order shall be available at the job site at all times during the sawing operation. Contracting joints shall not be sealed.

3.3.5 Expansion Joints: Transverse expansion joints shall be installed at sidewalk returns and opposite expansion joints in adjoining curbs. Where the sidewalk is not in contact with the curb, transverse expansion joints shall be installed as indicated. The 1/2 inch thick filler shall be installed in such a manner as to form a complete uniform separation between the structure and sidewalk pavement. The top edge of the filler strip shall be 1/4 inch below the surface and shall be held in place with steel pins or other devices to prevent warping of the filler during floating and finishing. At the end of the curing period, expansion joints shall be carefully cleaned and filled with joint sealer (no waxed base curing compound or joint surfaces to be sealed). Concrete at the joint shall be surface dry, and the atmospheric and pavement temperatures shall be above 50 degrees Fahrenheit at the time of application of joint-sealing materials. Joints shall be filled flush with the concrete surface in such a manner as to minimize spilling on the walk surface. Spilled sealing material shall be removed immediately and the surface of the walk cleaned. Expansion joints shall be formed about structures and the features that project through or into the concrete pavement.

3.4 CURB AND GUTTER CONCRETE PLACEMENT AND FINISHING:

3.4.1 Formed Curb and Gutter: Concrete shall be placed to the section required in a single lift. Consolidation shall be achieved by using approved mechanical vibrators.

3.4.2 Concrete Finishing: Exposed surfaces shall be floated and finished with a smooth wood float until true to grade and section and uniform in texture. Floated surfaces shall then be brushed with a fine-hair brush with longitudinal strokes. The edges of the gutter and top of the curb shall be rounded with an edging tool to a radius of 1/2 inch. Immediately after removing the front curb form, the face of the curb shall be rubbed with a wood or concrete rubbing block and water until blemishes, form marks, and tool marks have been removed. The front curb surface, while still wet, shall be brushed in the same manner as the gutter and curb top. The top surface of gutter and entrance shall be finished to grade with a wood float. Visible surface and edges of the finished curb, gutter, entrance, and combination curb and gutter shall be free of blemishes and form and tool marks and shall be uniform in color, shape, and appearance.

3.4.3 Joint Finishing: Expansion and contraction joints shall be constructed at right angles to the line of curb and gutter.

3.4.4 Contraction Joints (Sidewalks only): Contraction joints shall be constructed directly opposite contraction joints in abutting Portland cement concrete pavements and spaced so that monolithic sections between curb returns shall not be less than 5 feet nor greater than 15 feet in length. Contraction joints shall be constructed by means of 1/8-inch thick separators and of a section conforming to the cross section of the curb and gutter. Separators shall be removed as soon as practicable after concrete has set sufficiently to preserve the width and shape of the Joint and prior to finishing. Troopwalks shall not have contraction joints.

3.4.5 Expansion Joints: Expansion joints shall be formed by means of preformed expansion joint filler material cut and shaped to the cross section of curb and gutter. Expansion joints shall be provided in curb and gutter directly opposite expansion joints of abutting Portland cement concrete pavement, and shall be of the same type and thickness as joints in the pavement. Where curb and gutter do not abut Portland cement concrete pavement, expansion joints at least 1/2 inch in width shall be provided at intervals not exceeding 30 feet or to match existing area. For troopwalks, expansion joints at least 1/2 inch in width shall be provided at intervals not exceeding 20 feet. Expansion joints shall be provided in locations indicated. Expansion joints shall be sealed immediately following curing of the concrete or as soon thereafter as weather conditions permit. Expansion joints and the top l-inch depth of gutter contraction joints shall be sealed with joint sealer. The joint opening shall be thoroughly cleaned before the sealing material is placed. Sealing shall be done so that the material shall not be spilled on exposed surfaces of the concrete. Concrete at the joint shall be surface dry and atmospheric and concrete temperatures shall be above 50 degrees Fahrenheit at the time of application of joint sealing material. Excess material on exposed surfaces of the concrete shall be removed immediately and concrete surfaces cleaned.

3.4.6 Curb Forming Machine: Concrete shall be placed to the desired section in a single pass. When the paver approaches a header at the end of a paving segment, a sufficient amount of concrete shall be maintained ahead of the paver to allow a roll of concrete to spill over the header. The amount of extra concrete shall be sufficient to prevent the slurry that is formed and carried along ahead of the paver from being deposited adjacent to the header. The paver vibrators should be brought as close to the header as possible before they are lifted. Additional consolidation shall be provided by hand-manipulated vibrators when required. When the curb forming machine is operated between or adjacent to previously constructed curbs, provisions shall be made to prevent damage to the previous construction and the machine. Finished surface at the edges shall not produce an edge slump exceeding 0.25 inch over 85 percent of the finished work and 100 percent of the work shall not have an edge slump exceeding 0.75 inch.

3.4.7 Surface and Thickness Tolerances: Finished surfaces shall not vary more than 1/4 inch from the testing edge of a 12-foot straightedge. Permissible deficiency in section thickness will be up to 0.25 inch.

3.5 CURING AND PROTECTION:

3.5.1 General Requirements: Concrete shall be protected against loss of moisture and rapid temperature changes for at least 7 days from the beginning of the curing operation. Unhardened concrete shall be protected from rain and flowing water. All equipment needed for adequate curing and protection of the concrete shall be on hand and ready for use before actual concrete placement begins. Protection shall be provided as necessary to prevent cracking of the pavement due to temperature changes during the curing period.

3.5.1.1 Mat Method: The entire exposed surface shall be covered with two or more layers of burlap. Mats shall overlap each other at least 6 inches. The mat shall be thoroughly wetted with water prior to placing on concrete surface and shall be kept continuously in a saturated condition and in intimate contact with concrete for not less than 7 days.

3.5.1.2 Impervious Sheeting Method: The entire exposed surface shall be wetted with a fine spray of water and then covered with impervious sheeting material. Sheets shall be laid directly on the concrete surface with the light-colored side up and overlapped 12 inches when a continuous sheet is not used. The curing medium shall not be less than 18-inches wider than the concrete surface to be cured, and shall be securely weighted down by heavy wood planks, or a bank of moist earth placed along edges and laps in the sheets. Sheets shall be satisfactorily repaired or replaced if torn or otherwise damaged during curing. The curing medium shall remain on the concrete surface to be cured for not less than 7 days.

3.5.1.3 Membrane Curing Method: A uniform coating of white-pigmented membrane-curing compound shall be applied to the entire exposed surface of the concrete as soon after finishing as the free water has disappeared from the finished surface. Formed surfaces shall be coated immediately after the forms are removed and in no case longer than 1 hour after the removal of forms. Concrete shall not be allowed to dry before the application of the membrane. If any drying has occurred, the surface of the concrete shall be moistened with a fine spray of water and the curing compound applied as soon as the free water disappears. Curing compound shall be applied in two coats by hand-operated pressure sprayers at a coverage of approximately 200 square feet per gallon for both coats. The second coat shall be applied in a direction approximately at right angles to the direction of application of the first coat. The compound shall form a uniform, continuous, coherent film that will not check, crack, or peel and shall be free from pinholes or other imperfections. If pinholes, abrasion, or other discontinuities exist, an additional coat shall be applied to the affected areas within 30 minutes. Concrete surfaces that are subjected to heavy rainfall within 3 hours after the curing compound has been applied shall be re-sprayed by the method and at the coverage specified above. Areas where the curing compound is damaged by subsequent construction operations within the curing period shall be re-sprayed. Necessary precautions shall be taken to insure that the concrete is properly cured at sawed joints, and that no curing compound enters the joints. The top of the joint opening and the joint groove at exposed edges shall be tightly sealed before the concrete in the region of the joint is re-sprayed with curing compound. The method used for sealing the joint groove shall prevent loss of moisture from the joint during the entire specified curing period. Approved standby facilities for curing concrete pavement shall be provided at a location accessible to the job site for use in the event of mechanical failure of the spraying equipment or other conditions that might prevent correct application of the membrane-curing compound at the proper time. Concrete surfaces to which membrane-curing compounds have been applied shall be adequately protected during the entire curing period from pedestrian and vehicular traffic, except as required for joint-sawing operations and surface tests, and from any other possible damage to the continuity of the membrane.

3.5.2 Backfilling: After curing, debris shall be removed and the area adjoining the concrete shall be backfilled. graded, and compacted to conform to the surrounding area in accordance with lines and grades as described in the Task Order.

3.5.3 Protection: Completed concrete shall be protected from damage until accepted. The Contractor shall repair damaged concrete and clean concrete discolored during construction. Concrete that is damaged shall be removed and reconstructed for the entire length between regularly scheduled joints. Refinishing the damage portion shall not be acceptable. Removed damaged portions shall be disposed of as directed by the Contracting Officer.

3.6 FIELD QUALITY CONTROL:

3.6.1 General Requirements: The Contractor shall perform the inspection and tests described and meet the specified requirements for inspection details and frequency of testing. Based upon the results of these inspections and tests, the Contractor shall take the action and submit reports as required below, and any additional test to insure that the requirements of these specifications are met.

3.6.2 Concrete Testing: Preparation of all field-control samples and testing of samples shall be by the Contractor. A minimum of 2 cylinders per day’s pour shall be prepared for testing by certified testing laboratory. At least one concrete slump test, one air content test and one set of cylinders will be taken each day concrete is placed.

3.6.2.1 Strength Testing: The Contractor shall provide molded concrete specimens for strength tests. Samples of concrete placed each day shall be taken not less than once a day nor less than once for every 8 cubic yards of concrete. The samples for strength tests shall be taken in accordance with ASTM C 172. Cylinders for acceptance shall be molded in conformance with ASTM C 31 by an approved testing laboratory. Each strength test result shall be the average of two test cylinders from the same concrete sample tested at 28 days, unless otherwise specified or approved. Concrete specified on the basis of compressive strength will be considered satisfactory if the averages of all sets of three consecutive strength test results equal or exceed the specified strength, and no individual strength test result falls below the specified strength by more than 500 psi.

3.6.2.2 Air Content: Air content shall be determined in accordance with ASTM C 173 or ASTM C 231. ASTM C 231 shall be used with concretes and mortars made with relatively dense natural aggregates. Two tests for air content shall be made on randomly selected batches of each class of concrete placed during each shift. Additional tests shall be made when excessive variation in concrete workability is reported by the placing foreman or the Government inspector. If results are out of tolerance, the placing foreman shall be notified and he shall take appropriate action to have the air content corrected at the plant. Additional tests for air content will be performed on each truckload of material until such time as the air content is within the tolerance specified.

3.6.2.3 Slump Test: Two slump tests shall be made on randomly selected batches of each class of concrete for every 4 cubic yards, or fraction thereof, of concrete placed during each shift. Additional tests will be performed when excessive variation in the workability of the concrete is noted or when excessive crumbling or slumping is noticed along the edges of slip-formed concrete.

3.6.3 Grade Conformance Tests: Completed sidewalks and curb and gutter sections will be checked for conformance with plan grade requirements. For that purpose the completed section will be subdivided into segments of length such as a 300-foot section. The finished surface of sidewalks shall be tested by running a line of levels at intervals of 25 feet or less, longitudinally along the centerline, and at corresponding points 1 foot left and right of the centerline. Curb and gutter sections shall be tested by running a line of levels at 25-foot intervals or less. Curb and gutter elevations shall be recorded for edge of gutter, face of curb/flow line of gutter, and top of curb. The levels required will be run by the Contractor. Within 30 days after completion of concrete placement in the respective area, the Contractor will furnish a copy of the level notes to the Contracting Officer, and identify in writing, all areas defective in plan grade requirements. No pavement shall be placed adjacent to a defective curb and gutter section until such time as the defect is corrected.

One additional test cylinder shall be taken during cold weather and cured on site under same conditions as concrete it represents.

3.6.4 Surface Smoothness Determination: After the concrete has hardened sufficiently to permit walking thereon, but no later than 36 hours after placement, the surface of the completed section shall be tested by the Contractor, in the presence of the Contracting Officer or designated representative, with a 10-foot straightedge or other approved device, operated in such a manner as to reveal all surface irregularities exceeding the specified tolerances. The entire area of sidewalks shall be tested in both the longitudinal and the transverse direction on longitudinal parallel lines 3 feet apart or less and transverse lines 10 feet apart or less. Curb and gutter shall be tested in the longitudinal direction along the center of the gutter and top of curb. The straightedge shall be held in contact with the surface and moved ahead 1/2 the length of the straightedge for each successive measurement. Straightedge lines shall be carried continuously across joints. The height of high areas on pavement surfaces shall be determined by placing the center of the straightedge at the center of high areas, rocking the straightedge until one end comes in contact with the pavement, then measuring the distance between the pavement surface and the bottom of the straightedge at the opposite end-, and taking one-half the distance as the height of the high area. Other devices that reveal surface irregularities exceeding specified tolerances may be used when approved.

3.6.5 Edge Slump Determination: After the concrete has hardened sufficiently to permit walking thereon, the surface shall be tested with a 10-foot straightedge or other approved device to reveal irregularities exceeding the edge slump requirements. The edge slump shall be determined at each edge of each sidewalk or curb and gutter constructed. Measurements shall be made at 5- to 25-foot spacing commencing at the header where paving is initiated. The measurements shall be made by the Contractor, in the presence of the Contracting Officer or designated representative, and will be properly referenced in accordance with established paving lane identification of the adjacent slab and stationing.

3.6.6 Thickness Evaluation: The anticipated thickness of the concrete shall be determined prior to placement by passing a template through the formed section or by measuring the depth of opening of the extrusion template of the curb forming machine. If a slip form paver is used for sidewalk placement, the subgrade shall be true grade prior to concrete placement and the thickness will be determined by measuring each edge of the completed slab.

3.6.7 Surface Evaluation: The finished surface of each category-of the completed work shall be uniform in color and free of blemishes and form or tool marks.

3.7 SURFACE DEFICIENCIES AND CORRECTIONS:

3.7.1 Thickness Deficiency: When measurements indicate that the completed concrete section is deficient in thickness by more than 0.25 inch the deficient section will be removed, between regularly scheduled joints, and replaced.

3.7.2 High Areas: In areas not meeting surface smoothness and plan grade requirements, high areas shall be reduced either by rubbing the freshly finished concrete with carborundum brick and water when the concrete is less than 36 hours old or by grinding the hardened concrete with an approved surface grinding machine after the concrete is 36 hours old or more. The area corrected by grinding the surface of the hardened concrete shall not exceed 5 percent of the area of any integral slab, and the depth of grinding shall not exceed 1/4 inch. All pavement areas requiring grade or surface smoothness corrections in excess of the limits specified above shall be removed and replaced.

3.7.3 Excessive Edge Slump: High areas revealed by the edge slump measurements will be subject to the tolerances specified. The concrete within the limits of excessive edge slump will be removed and replaced. Partial slabs removed and replaced shall extend across the full width of the section.

3.7.4 Appearance: Exposed surfaces of the finished work will be inspected by the Government and any deficiencies in appearance will be identified. Areas which exhibit excessive cracking, discoloration, form marks, or tool marks or which are otherwise inconsistent with the overall appearances of the work shall be removed and replaced.

3.8 REMOVAL AND REPLACEMENT OF DEFECTIVE CONCRETE:

3.8.1 Defective Concrete: Defective concrete or damaged concrete shall be removed and replaced as specified herein, and a method of curing shall be employed as directed. All removed concrete shall be replaced with concrete of the thickness and quality required by these specifications. In no case shall the removal and replacement of concrete result in a slab less than the full sidewalk or curb and gutter width or a joint less than 5 feet from a regularly scheduled transverse joint. The defective concrete shall be removed carefully so that the adjacent section is not damaged. When a portion of the unfractured slab is replaced, a full depth saw cut shall be made transversely across the slab in the required location, and the concrete shall be removed to provide a vertical face in the remaining portion of the slab. Prior to placement of the fresh concrete, the face of the slab shall be cleaned of debris and loose concrete. Transverse joints of the replaced slab or portion thereof shall be constructed as indicated. The joints shall be sealed as specified. Removal and replacement of defective or damaged concrete shall be accomplished by the Contractor at no additional cost to the Government.

3.8.2 Appearance: Areas which exhibit excessive cracking, discoloration, form marks, or tool marks or which are otherwise inconsistent with the overall appearances of the work shall be removed and replaced. The finished surface of the completed work shall be uniform in color and free of blemishes and form or tool marks. Prior to acceptance all concrete including brick surfaces shall be thoroughly cleaned.

3.9 ETCHING OF CURBS: Following the entire installation procedure, or as soon as the concrete is sufficiently cured, the curbs should be etched in order to mark the location of any underground cables, sleeves, etc., that were encountered or installed for future reference. The markings will be on the back side of the curb and should include a small arrow pointing down to the location. Above this arrow in one inch lettering, one of the following letter codes should be etched using an inscribing tool of some kind:

CODE

DESIGNATION

G

Gas

SS

Sanitary Sewer

SD

Storm Drain

CM

Communications

SV

Sleeve

E

Underground Electrical

END OF SECTION

Section 02511 – Page 13 of 15