County-Specs-02520-Concrete-Paving-and-Curbs.pdf

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GREENVILLE COUNTY

PUBLIC WORKS

STANDARD SPECIFICATIONS

SECTION 02520

CONCRETE PAVING

AND CURBS

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CONCRETE PAVING AND CURBS

SECTION 02520

RELATED DOCUMENTS: Attention is directed to related sections of the Specifications, as they pertain to the guidelines, materials, and methods described in this section. Also, the General Provisions and Special Provisions of the Contract shall apply to all Sections of the Work.

1.0 SCOPE:

a. General Requirements: The Contractor shall furnish all labor, materials, formwork, equipment, and services required to complete all the concrete work shown on the drawings and specified herein, including all sidewalks, concrete pavements, ramps, and curbs.

2.0 MATERIALS:

a. Delivery and Storage of Materials: Do not deliver concrete until vapor barrier, forms, reinforcement, embedded items, and chamfer strips are in place and ready for concrete placement. Concrete shall be stored so as to prevent deterioration of contamination.

Aggregates shall be stored and handled so as to preserve the gradation and cleanliness of the material. Store reinforcement of different sizes and shapes in separate piles on racks raised above the ground to avoid excessive rusting. Protect from contaminants such as grease, oil, and dirt. Provide for accurate identification after bundles re broken and tags removed.

b. Cement: Cement shall conform to the latest revised Standard Specification for Portland

Cement, American Society for Testing and Materials, (ASTM) C-150, or Standard Specification for Blended Hydraulic Cements, ASTM C-595. Cement shall correspond to that cement on which the selection of concrete proportions was based.

c. Aggregates: Concrete aggregates shall conform to the latest revised Standard

Specifications for Concrete Aggregates, ASTM C-33. Maximum coarse aggregate size shall not be more than one fourth the slab thickness.

d. Water: All mixing water shall be clean and free from deleterious amounts of acids, alkalies, or organic materials.

e. Expansion Joints: Expansion joint material where required shall be 1/2 inch thick asphalt-impregnated premolded fiber conforming to the latest Standard Specification for Preformed Expansion Joint Filler for Concrete, ASTM D-1752.

f. Curing Compound: Curing compound shall conform to the latest revised Standard Specifications for Liquid Membrane-Forming compounds for Curing concrete, ASTM C-309.

g. Admixtures: Air-entraining admixtures for concrete shall conform to the latest revised

Standard Specifications for Air-Entraining Admixtures for Concrete, ASTM C-260.

h. Concrete: All concrete shall have a minimum 28-day compressive strength of 3000 psi.

Concrete shall be manufactured and delivered in accordance with the latest revised Standard Specification for Ready Mixed Concrete, ASTM C-94.

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1. Minimum Cement Content: Concrete shall be produced with a minimum cement content of 520 lbs. per cubic yard and an entrained air content of 6% plus or minus 1-1/2% by volume.

2. Maximum Slump: Maximum allowable concrete slump shall be 4 inches.

i. General: All other materials used in the concrete shall conform to current applicable ASTM specifications.

j. Forms: Forms shall be of wood, plywood, or steel. Wood forms, for surfaces exposed to view in the finished structure and requiring a smooth finish, shall be plywood. For unexposed surfaces, undressed square-edge lumber may be used. Surfaces of steel forms shall be free from irregularities, dents, and sags.

k. Reinforcement: Metal reinforcement shall be provided in accordance with the drawings.

Shop drawings for reinforcing steel may be required which indicate bending diagrams, assembly diagrams, splicing and laps of bars, shapes, dimensions, and details of bar reinforcing, accessories, and concrete cover. Do not scale dimensions from drawings to determine lengths of reinforcing rods.

Reinforcing steel shall conform to ASTM A-615, Specifications for Deformed Billet Steel Concrete Reinforcing, and shall be grade 60. Welded Wire fabric shall conform to ASTM A-185, Standard specifications for welded Steel Wire Fabric for Concrete Reinforcement.

l. Vapor Barrier: Vapor barrier material when specified shall be either reinforced Kraft paper or new unplasticized polyethylene film, 6 mils thick minimum.

m. Gravel: Gravel when indicated as fill under concrete slabs shall consist of clean crushed stone, crushed gravel, and uncrushed gravel, 3/4 inch maximum size and 0-5 percent passing a No.4 sieve. The gravel shall be placed directly on the subgrade.

3.0 CONSTRUCTION

a. Subgrade Preparation: The bottom of the excavation or the top of the fill shall be known as the pavement subgrade and shall conform to the lines, grade, and cross sections shown in the plans.

1. Removal of Unsuitable Material: All soft and yielding material and portions of the subgrade that will not compact readily when rolled or tamped shall be removed and replaced with suitable material.

2. Compaction: The subgrade shall be brought to a firm and unyielding condition by compacting it to uniform density. Soil should be compacted at or slightly above standard optimum moisture.

3. Concrete Placement: Concrete shall not be placed on a soft, spongy, frozen, or otherwise unsuitable subgrade. The subgrade shall be moist when concrete is placed.

b. Forms: Formwork shall be in accordance with ACI 347. Coordinate formwork construction with installation of work of other trades to insure adequate placement of materials, sleeves, inserts, and accessories in proper location.

1. Formwork Support: The Contractor shall be fully responsible for adequacy of formwork in its entirety. Forms shall support loads they will be required to sustain and shall maintain their dimensional and surface correctness to produce structures required by the drawings. Immediately before the placing of reinforcing, faces of all forms in

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contact with the concrete shall receive a thorough coating of a liquid form releasing agent.

2. Neat Excavation for Footings, Form Alignment, and Chamfering Exposed Edges of

Concrete: Concrete for footings may be placed in excavations without forms upon inspection and approval. Excavation width shall be a minimum 4 inches greater than indicated. Set forms mortar-tight and true to line and grade. Provide 3/4 inch chamfers on all above-grade exposed joints, edges, and external corners unless otherwise indicated.

3. Removal of Forms: Prevent concrete damage during form removal. After placing concrete, forms shall remain in place for a minimum of 24 hours. In no case shall supporting forms or shoring be removed until members have acquired sufficient strength to support their weight and imposed loads safely.

c. Reinforcement:

1. Placing Reinforcement and Misc. Materials: Provide bars, wire fabric, wire ties, supports, and other devices necessary to install and secure reinforcement.

Reinforcement shall not contain rust, scale, oil, grease, clay, and foreign substances that would reduce the bond. Rusting of reinforcement is a basis of rejection if the effective cross sectional area or the nominal weight per foot of the reinforcement has been reduced to less than specified. Remove loose rust prior to placing steel. Tack welding is prohibited.

2. Reinforcement Protection: The reinforcement shall be protected by the thickness of concrete indicated on the plans. Where not otherwise shown the thickness of concrete over the reinforcement shall be as follows:

a. Where concrete is deposited against the ground without the use of forms then not less than three (3) inches.

b. Where concrete is exposed to the weather, submerged, or exposed to the ground, but placed in forms then not less than two (2) inches for bars larger than No. 5 and not less than 1-1/2 inches for No.5 bars and smaller.

3. Wire Mesh Installation: Install and properly support wire mesh reinforcing within two (2) inches of top of concrete slabs on ground and as otherwise indicated. Lap all joints six

(6) inches and wire securely. Extend mesh to within two (2) inches of sides and ends of slabs.

4. Tolerances: Place reinforcement and secure with galvanized or noncorrodible chairs, spacer, or metal hangers. Use concrete or other noncorrodible material for supporting reinforcement on the ground.

5. Setting Anchors and Miscellaneous Material: Place and secure anchors and bolts, pipe sleeves, conduits, and other such items in position before concrete placement where possible. Plumb anchor bolts and check location and elevation. Temporarily fill voids in sleeves with readily removable material to prevent the entry of concrete.

d. Concrete Placement: Place concrete as soon as practicable after the forms and the reinforcement have been inspected and approved. Ready mixed concrete hauled in truck mixers or truck agitators shall be deposited in place within 90 minutes from the time water is added to the mix. Do not place concrete when weather conditions prevent proper placement and consolidation; in uncovered areas during periods of rainfall; or in standing water. Prior to placing concrete, remove dirt, construction debris, water, snow, and ice

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from within the forms. Deposit concrete as close as practicable to the final position in the forms. Do not exceed a free vertical drop of three (3) feet from the point of discharge.

Place concrete in one continuous operation until placement of the section is completed.

1. Consolidation: Consolidate placed concrete using mechanical vibrating equipment with hand rodding and tamping, so that concrete is worked around reinforcement and other embedded items and into all parts of the forms.

2. Protection: Protect concrete from physical damage and reduced strength due to weather extremes. In cold weather comply with ACI 306 and in hot weather comply with ACI 305.

e. Joints: Provide construction, expansion, and control joints as indicated or required. Locate construction joints so as to not impair the strength and appearance of the structure. Place expansion and control joint in slabs on grade to stabilize differential settlement and random cracking.

1. Expansion Joints: Expansion joints shall be located where slabs meet with a vertical wall surface, to isolate fixed objects, at fifty (50) foot intervals unless indicated otherwise and where indicated on the drawings.

2. Control Joints: Unless otherwise shown, control joints shall be installed at uniform intervals not to exceed twenty (20) feet. Control joints or contraction joints shall be formed by one of the following methods: sawing, forming by hand, forming by premolded filler or using full depth construction joints. Joint depth shall be minimum of 1/4 the slab thickness. Hand formed joints shall have a maximum edge radius of 1/4 inch. Sawing of joints shall begin as soon as the concrete has hardened sufficiently to permit sawing without successive raveling. All joints shall be completed before uncontrolled shrinkage cracking occurs. Joints shall be continuous across the slab, unless interrupted by full-depth premolded joint filler.

3. Construction Joints: Construction joints, as required, shall be located at control joint locations. The construction joint shall be keyed and bond between successive pours shall be broken with curing compound.

f. Waterstops: Waterstops in joints, where indicated, shall be polyvinylchloride of types as shown on the drawings.

g. Finishes of Formed Surfaces: Concrete surfaces which will be exposed to view in the completed work, including tops of walls and curbs, shall be given a smooth-rubbed finish.

Provide on newly hardened concrete within 24 hours following form removal. Wet surfaces and rub with an abrasive tool to produce uniform color and texture. Use only the cement paste drawn from the concrete rubbing process.

h. Concrete Finishing: After concrete has been struck off and consolidated, a bull float may be used to obtain the proper contour, grade, and elevation before bleed water appears.

Bull float use shall be confined to a minimum. Permit concrete to attain a set sufficient for floating and supporting the weight of the finisher and equipment. If bleed water is present prior to floating the surface, drag the excess water off or remove by absorption with porous materials. Do not use dry cement to absorb bleed water. Provide a broomed finish for exterior walks, platforms, patios, and ramps, unless otherwise indicated. Provide a floated finish, then finish with a flexible bristle broom. Permit surface to harden sufficiently to retain the scoring or ridges. Broom transverse to traffic or at right angles to the slope of the slab.

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1. Pavement: After screeding, float the concrete longitudinally. Use a straight edge to check slope and flatness; correct and refloat as necessary. Obtain final finish by a burlap drag. Drag a strip of clean, wet burlap across the slab to produce a fine, granular, or sandy textured surface without disfiguring marks. Round edges and joints with an edger having a radius of 1/8 inch.

2. Concrete Walks: Provide four (4) inches thick minimum. Provide contraction joints spaced every 5 linear feet unless otherwise indicated. Cut contraction joint one (1) inch deep with a jointing tool after the surface has been finished. Provide 1/2 inch thick transverse expansion joints at changes in direction where sidewalks abuts curb, steps, rigid pavement, or other similar structures; space expansion joints every fifty (50) feet maximum apart. Provide walks with a broomed finish. Provide a transverse slope of 1/4 inch per foot.

3. Curbs: Curbs shall be constructed as indicated on the drawings and in accordance with

Section 720 of the SCHD SSHC. Provide contraction joints spaced every ten (10) feet maximum unless otherwise indicated and at the beginning and ending of radii. Cut contraction joints 3/4 to 1 inch deep with a jointing tool after the surface has been finished. Provide expansion joints 1/2 inch thick and spaced every 100 feet maximum unless otherwise indicated. Provide a smooth rubbed finish.

i. Curing: Concrete shall be cured by protecting it from loss of moisture, rapid temperature change, and mechanical injury for at least three days after placement. After all free water has disappeared from the surface, a liquid membrane-forming compound or other approved curing material shall be uniformly sprayed on all exposed surfaces. Rate of application shall be in accordance with manufacture's recommendations. Surfaces to receive finishes set in Portland cement setting beds shall be covered with polyethylene or reinforced Kraft paper, or with sand. Do not use spray on curing compound. Lap Kraft paper, and keep weighted down to prevent evaporation. Keep sand moist.

j. Opening to Traffic: Pavement shall be closed to traffic for at least three full days or until such time that the minimum compressive strength of the concrete is at least 75% of its design strength.

k. Testing: The Contractor shall be responsible for sampling and testing of concrete as necessary to meet the minimum strength and material requirements of these specifications, as directed by the Engineer. Testing shall be performed by a certified independent testing laboratory.

END OF SECTION