SECT-38_CONCRETE.docx

SECTION 38 - CONCRETE

Item No. Title

38.4 CONCRETE GUTTER, CURB ELEMENTS, AND TRAFFIC SEPARATORS

38.5 CONCRETE SIDEWALK

38.1 GENERAL

38.1.1 SCOPE OF WORK

The work specified in this Section consists of furnishing all material, transportation, tools, labor, and equipment, unless otherwise specified, to construct all cast-in-place concrete indicated on the drawings and includes but is not necessarily limited to footings, foundations, walls, slabs, block cell fill, exterior flat work, curb and gutter, and sidewalk work.

38.1.2 QUALIFICATIONS OF WORKMEN

Provide at least one person at all times during excavation of this portion of the work who is thoroughly trained and experienced in placing the types of concrete specified to direct all work performed under this Section. For finishing of exposed surfaces of the concrete, use only thoroughly trained and experienced journeyman concrete finishers.

38.1.3 PLANT QUALIFICATION

Meet all requirements of the Check List for Certification of Ready Mixed Concrete Production Facilities of the National Ready Mixed Concrete Association and ASTM C-94.

38.1.4 STANDARDS

1.) Unless otherwise indicated, all materials, workmanship, and practices shall conform to the requirements of the following standards:

a.) Standard Building Code (latest edition), Chapter XVI b.) ACI 301 (latest edition), "Structural Concrete for Buildings" c.) ACI 318 (latest edition), "Building Code Requirements for Reinforced Concrete"

2.) Where provisions of pertinent codes and standards conflict with this specification, the more stringent provisions shall govern.

38.1.5 SUBMITTALS

Submit the following information to the PROJECT ENGINEER for review. Furnish no concrete until submittals have been reviewed.

1.) Plant Qualifications: Submit satisfactory evidence indicating compliance with the specified qualification requirements.

2.) Materials: Submit satisfactory evidence indicating that all materials listed in Part 2 meet the specified requirements.

3.) Design Mix: Submit the design mix to be used for review at least 15 days prior to the desired beginning of placing concrete. The design of the mix is the responsibility of the Contractor, subject to the limitations of the specifications. Review of this submission will be interpreted only that the minimum requirements of the specifications have been met. Such review will in no way alter the responsibility of the Contractor to furnish concrete meeting the requirements of the specifications relative to strength, slump, cement content, and water/ cement ratio.

38.1.6 TRANSIT-MIX DELIVERY SLIPS

Keep a record at the job site showing time and place of each pour of concrete, together with transit-mix delivery slips certifying contents of the pour. Make the record available to the PROJECT ENGINEER for his inspection upon request. Upon completion of each portion of the work, deliver a copy of the record and the delivery slips to the PROJECT ENGINEER.

38.2 PRODUCTS

38.2.1 CONCRETE

1.) General: Use ready-mixed concrete, batched, mixed, and transported in accordance with ASTM C-94 unless otherwise indicated.

2.) Cement: For all concrete use domestic Portland cement that conforms to the requirements of ASTM Designation C-150, Type I, Type II, or Type III. Use Type II cement for all concrete that is to come in contact with sewage and for concrete piles. Use Type III cement for high early strength concrete only for special locations and only when reviewed in advance by the PROJECT ENGINEER. Use Type I cement for tremie concrete.

Use only one brand of cement in any individual structure. Use no cement, which has become damaged, partially set, lumpy, or caked. Reject the entire contents of the sack or container, which contains such cement. Use no salvaged or reclaimed cement.

3.) Aggregate: Use fine and coarse aggregates that are clean, hard, natural, or manufactured material conforming to ASTM C-33, size #57, except block cell fill, size #8.

The nominal maximum size of the aggregate shall be in accordance with ACI 318, Chapter 3.

4.) Water: Use potable water, free from deleterious materials.

5.) Air Entraining Admixture: Unless otherwise specified, provide concrete containing air entraining admixture conforming to ASTM C-260.

Determine the amount of air entrainment in accordance with Chapter 4 of ACI 318.

6.) Water Reducing and Retarding Admixture: Water reducing and retarding admixtures may be used. When used, the admixtures must be in accordance with ASTM C-494 and stored and batched in accordance with the manufacturer's recommendations. Do not use calcium chloride or any other admixture containing chloride salts.

7.) Quality: Unless otherwise specified, all concrete shall have the following minimum compressive strengths at 28 days and shall be proportioned for strength and quality requirements in accordance with ACI 318-77, Section 4.3, "Proportioning on the Basis of Field Experience", to achieve 28-day compressive strength as follows:

8.) All mixes to contain an ASTM C-494 water reducer admixture.

9.) Water Cement Ratio: The maximum permissible water cement ratio is to be in accordance with Chapter 4 of ACI 318.

10.) Concrete for below grade structure to be integrally water-proofed with "Ipanex", by IPA Systems, Inc., or equivalent.

38.2.2 VAPOR BARRIER

Polyethylene film 0.006 inches thick conforming to Product Standard PS-17.

38.2.3 BOND BREAKER

Thirty pound asphalt impregnated roofing felt. For use between slabs and walls where expansion joint is not required.

38.2.4 GRANULAR BASE

Shall conform to ASTM D-1241, Type I, gradation B.

38.2.5 OTHER MATERIALS

Select all other materials not specifically described but required for a complete and proper installation for cast-in-place concrete subject to the review of the PROJECT ENGINEER.

38.3 EXECUTION

38.3.1 NOTIFICATION

Notify the PROJECT ENGINEER at least 48 hours prior to desired time of placing concrete.

38.3.2 ACCEPTABILITY

Place no concrete until the PROJECT ENGINEER has observed the forms and reinforcing work. Thoroughly clean forms and set reinforcing and all other items required to be in concrete. Make sure they are thoroughly secured.

38.3.3 PREPARATIONS

1.) Inspection: Prior to all work of this section, carefully inspect the installed work of all other trades and verify that all such work is complete to the point where this installation may properly commence. Verify that all items to be embedded in concrete are in place. Verify that concrete may be placed to the lines and elevations indicated on the drawings with all required clearance from reinforcement.

2.) Discrepancies: In the event of discrepancy, immediately notify the PROJECT ENGINEER. Do not proceed with installation in areas of discrepancy until such discrepancies have been fully resolved.

3.) Subgrade: The subgrade and/or bedding shall be compacted and free of frost. If placement is allowed at temperature below freezing, provide temporary heat and protection as required to remove all frost. Saturate the subgrade approximately 8 hours before placement and sprinkle ahead of the placement of concrete in areas where vapor barrier is not used. Remove all standing water, ice, mud, and foreign matter before concrete is deposited. Provide mud slabs where necessary to obtain a dry and stable working platform for placement of slabs.

4.) Granular Base: When indicated on the plans, install granular base beneath the slab on grade or a structural foundation. Place the granular material on a subgrade compacted to 95% relative compaction as per Section 02223 and compact the granular base to the same density.

5.) Vapor Barrier: On porous subgrade or bedding, or where indicated on the drawings, provide vapor barrier. Lay vapor barrier sheets with 6-inch edge laps and tape or seal with mastic. Stretch and weight edges and laps to maintain their positions until concrete is placed.

6.) Forms and Tools: Remove all wood scraps and debris from the areas in which concrete will be placed. Thoroughly clean the areas to ensure proper placement and bonding of concrete. Thoroughly wet the forms (except in freezing weather) or oil them. Remove all standing water. Thoroughly clean all transporting and handling equipment.

38.3.4 CONVEYING CONCRETE

1.) General: Convey concrete from the truck to the place of final deposit as rapidly as practicable by methods which will prevent segregation or loss of ingredients to maintain the quality of the concrete. Place no concrete more than 90 minutes after mixing has begun for the particular batch.

2.) Buckers and Hoppers: Use buckets and hoppers that have discharge gates with a clear opening equal to no less than one-third of the maximum interior horizontal areas or five times the maximum aggregate size being used. Side slopes shall be no less than 60o. Controls on gates shall permit opening and closing during the discharge cycle.

3.) Elephant Trunks: Use hoppers and elephant trunks or drop chutes to prevent the free fall of concrete that results in separation of coarse particles.

4.) Chutes: Use metal or metal lines chutes with a slope not exceeding one vertical to two horizontal and not less than one vertical to three horizontal. Chutes more than 20 feet long and chutes not meeting the slope requirement may be used only if they discharge into a hopper before distribution.

5.) Pumping Equipment: Pumping equipment and procedures, if used, shall conform to the recommendations contained in the report of ACI Committee 304 on "Placing Concrete by Pumping Methods". Measure the specified slump at the point of discharge. The loss of slump in pumping shall not exceed 1 to 1-1/2 inches.

6.) Cleaning: Clean conveying equipment at the end of each concrete operation.

38.3.5 PLACING CONCRETE

1.) General: Place all concrete in the dry and deposit concrete continuously, or in level layers of such thickness (not exceeding 2 feet in depth) that no concrete will be deposited on concrete that has hardened sufficiently to cause the formation of seams, plans of weakness, or cold joints.

2.) Segregation: Deposit concrete as nearly as practicable in its final position to avoid segregation due to re-handling or flowing. Do not subject concrete to procedure, which will cause segregation. Maximum free fall of concrete is 3 feet.

38.3.6 CONSOLIDATING CONCRETE

1.) General: Consolidate concrete by means of internal vibrators operated by competent workmen. Other means must have been reviewed by the PROJECT ENGINEER to determine acceptability prior to implementing.

2.) Vibrators: Provide adequate vibrators for the project. Use vibrators having sufficient intensity and duration to cause complete consolidation of concrete. Provide at least one spare vibrator for up to three vibrators being used and one for each three additional vibrators.

3.) Use of Vibrators: Use vibrators to consolidate properly placed concrete. Do not use vibrators to move concrete in the forms. Insert vibrators in the surface of concrete at points spaced to insure uniform vibration of the entire mass of the concrete and no further apart than the radius over which the vibrator is visibly effective. Allow the vibrator to sink into the concrete by its own weight to penetrate into the underlying layer sufficiently so that the two layers are thoroughly consolidated together. When the paste first appears near the top of the vibrator head (usually within 5 to 15 seconds), withdraw the vibrator vertically at about the same rate that it descended.

Do not leave the vibrator immersed in concrete after the paste accumulates over the head, as this results in non-uniformity.

38.3.7 CONCRETE TESTING

1.) The Owner will retain an independent testing laboratory.

2.) Compressive Strength: Standard laboratory compressive test cylinders are to be obtained in accordance with ASTM C-172 by the laboratory when concrete is discharged from the mixer at the point of placing, and cylinders made and cured in accordance with the requirements of ASTM, Designation C-31. Obtain a set of 3 cylinders for each 75 cubic yards or fraction thereof placed each day, for each type of concrete. Cure the cylinders under laboratory conditions and test in two groups, one at 7 and two at 28 days of age respectively, in accordance with the requirements of ASTM Designation C-39. Evaluation and acceptance of concrete will be determined by the PROJECT ENGINEER in accordance with ACI 318, Chapter 4.

3.) Slump: Slump tests are to be made by the laboratory for each 25 cubic yards or for each concrete placement. Make slump tests in accordance with ASTM C-143. Failure to meet specified slump requirements will be sufficient cause for rejection of that batch. Slump test must be made after any water is added in the field.

4.) Air Content: Make tests for air content of concrete in accordance with ASTM C-231 or ASTM C-173 at least once a day.

38.3.8 PROTECTION OF CONCRETE

Comply with ACI 305 and 306 for protecting and curing concrete in hot and cold weather. Do not allow rain water to increase the mixing water or to damage the surface finish. Protect concrete from construction overloads. Do not apply design loads until the specified strength has been attained and verified by test cylinder breaks, or before 28 days, whichever results in the longer time period.

38.3.9 BONDING TO EXISTING SURFACES

Clean existing concrete surfaces that are to have new concrete bonded thereto of all grease, oil, dust, dirt, and loose particles and coat with an epoxy bonding agent just prior to placing of the new concrete. Do not overlap or spill bonding agent on the surfaces to be exposed after the work is complete.

38.3.10 EMBEDDED ITEMS

Build into, set in, or attached to form pipes, inserts, and other metal objects as shown, specified, or ordered prior to concrete placement. Take all necessary precautions to prevent these objects from being displaced, broken, or deformed. Before concrete is placed, take care to determine that all embedded parts are firmly and securely fastened in place as indicated. Thoroughly clean and remove paint or other coating, rust, scale, oil, or any foreign matter from embedded parts. Embed no wood in concrete. pack the concrete tightly around pipes and other metal work to prevent leakage and to secure adhesion. Protect drains from intrusion of concrete.

38.3.11 HOT WEATHER CONCRETING

The Contractor shall take appropriate measures as described in ACI-305-72 "Recommended Practice for Hot Weather Concreting," for those instances when the concrete might exceed 90 F at time of placement.

38.4 CONCRETE GUTTER, CURB ELEMENTS AND TRAFFIC SEPARATORS

A.) Description: The work specified in this section consists of the construction of Portland cement concrete curb and gutter, concrete traffic separator, valley gutter, special concrete gutter, and any other types of concrete curb. The various items shall be constructed in accordance with these specifications and in conformity with the lines, grades, dimensions, and notes shown in the plans.

B.) Materials:

1.) Concrete: All work under this section shall be of concrete that will have a minimum strength of 2,500 psi in twenty-eight days. Concrete shall not be mixed or placed under adverse weather conditions.

2.) Joint Materials: Joint materials for the various items shall be in accordance with AASHTO M 153 or AASHTO M 213.

C.) Forms:

1.) Form Materials: Forms for this work shall be made of either wood or metal. They shall be straight, free from warp or bends and of sufficient strength, when staked, to resist the pressure of the concrete without deviation from line and grade. For all items constructed on a radius, the CONTRACTOR will be required to use flexible forms, unless otherwise permitted by the PROJECT ENGINEER.

2.) Depth of Forms: Forms shall have a depth equal to the plan dimensions for the depth of concrete being deposited against them.

3.) Machine Placement; Placing of these items by machine methods may be allowed with the approval of the PROJECT ENGINEER, provided that an acceptable finished product, true to line, grade and crossection, is consistently produced.

D.) Excavation: Excavation shall be to the required depth, and the foundation material upon which these items are to be placed shall be compacted.

E.) Placing Concrete: The concrete shall be placed in the forms and tamped and spaded to prevent honeycomb and until the top of the structure can be floated smooth and the edges rounded to the radius shown in the plans.

F.) Joints: Contraction joints shall be placed as shown in the plans or Standard Indexes.

G.) Expansion Joints: Expansion joints shall be constructed at all inlets, at all radius points, and at other locations indicated in the plans. They shall be located at intervals of 500 feet between other expansion joints or ends of a run. The joint shall be 1/2 inch in width.

H.) Finishing:

1.) Repair of Minor Defects: The forms shall be removed within 24 hours after the concrete has been placed, and minor defects then filled. Plastering will not be permitted on the face of the curb, and any rejected curb, curb and gutter, or valley gutter shall be removed and replaced without additional compensation.

2.) Final Finish: All exposed surfaces shall be given a brush finish.

I. Curing: The concrete shall be continuously cured for a period of at least 72 hours by a method approved by the PROJECT ENGINEER. After forms are removed, the surfaces exposed shall be cured by placing a berm of moist earth against them or by any of the methods approved by the PROJECT ENGINEER.

J. Backfilling and Compaction: After the concrete has set sufficiently, but not later than three days after pouring, the spaces in front and back of the curb shall be refilled to the required elevation, with suitable material, which shall be placed and thoroughly compacted.

K.) Method of Measurement: The quantities to be paid for under this section shall be the lengths in feet of concrete curb, concrete curb and gutter, concrete traffic separator, special concrete gutter, concrete valley gutter and concrete shoulder gutter, as determined by plan dimensions.

L.) Basis of Payment: The quantities, determined as provided above, shall be paid for at the contract unit prices per linear foot for concrete curb, concrete curb and gutter, concrete traffic separator, special concrete gutter, concrete valley gutter and concrete shoulder gutter. Such prices and payments shall be full compensation for all the work specified in this section.

Backfill and excavation will not be paid for separately.

Reinforcing steel shall not be paid for separately.

The cost of all joint materials shall be included in the contract unit price for the item in which they are used.

Payment shall be made under items:

38.5 CONCRETE SIDEWALK

A.) Description: The work specified in this section consists of the construction of concrete sidewalk and curb cut ramps in accordance with these specifications and in conformity with the lines, grades, dimensions and notes shown in the plans.

B.) Materials:

1.) Concrete: All work under this section shall be concrete that will have a minimum strength of 2,500 psi in twenty-eight (28) days. The CONTRACTOR shall assume all risk when placing concrete under extreme weather conditions and permission to place concrete will in no way relieve the CONTRACTOR of the responsibility of satisfactory results.

2.) Reinforcement: Where the plans call for steel reinforcement to be placed in the sidewalk, it shall conform to the plans and Standard Indexes.

C.) Forms: Forms for this work shall be made of either wood or metal and shall have a depth equal to the plan dimensions for the depth of concrete being deposited against them. They shall be straight, free from warp or bends, and of sufficient strength, when staked, to resist the pressure of the concrete without deviation from line and grade. Forms shall be cleaned each time they are used and shall be oiled or saturated with water prior to placing the concrete.

D.) Foundation: Excavation or fill shall be made to the required grade, and the foundation material upon which the sidewalk is to be set shall be compacted to a firm even surface, true to grade and crossection, and shall be moist at the time the concrete is placed.

E.) Joints: Expansion joints between the sidewalk and the curb or driveway or at fixed objects and sidewalk intersections shall be 1/2 inch joints, formed with a preformed joint filler.

Contraction joints may be of the open type or may be sawed. Open-type contraction joints shall be formed by staking a metal bulkhead in place and depositing the concrete on both sides. After the concrete has set sufficiently to preserve the width and shape of the joint, the bulkhead shall be removed. After the sidewalk has been finished over the joint, the slot shall be edged with a tool having a 1/2 inch radius.

Sawed Joints: If the CONTRACTOR elects to saw the contraction joints, a slot approximately 3/16 inch wide and not less than 1-1/2 inches deep shall be cut with a concrete saw after the concrete has set, and within the following periods of time.

Joints at not more than thirty foot (30') intervals - within twelve (12) hours after finishing. Remaining joints - within ninety-six (96) hours after finishing.

F.) Finishing:

1.) Screeding: The concrete shall be struck-off by means of a wood or metal screed, used perpendicular to the forms, in order to obtain the required grade and remove surplus water and laitance.

2.) Surface Requirements: The concrete shall be given a broom finish. The surface variations shall not be more than 1/4 inch under a ten foot (10') straight edge, nor more than 1/8 inch on a five foot (5') transverse section. The edge of the sidewalk shall be carefully finished with an edging tool having a radius that shall match the existing sidewalk.

G.) Curing: The concrete shall be cured for 72 hours by a method approved by the PROJECT ENGINEER.

H.) Clean-Up: Upon completion of work, and before final payment is made, the CONTRACTOR shall remove from the job site any surplus or discarded materials or rubbish and shall restore the job site area to a condition acceptable to the CITY. Unless otherwise specified in writing by the PROJECT ENGINEER, the disposal of concrete rubble shall be the responsibility of the CONTRACTOR. When it is specified that the concrete rubble is to be retained by the CITY, it shall be stockpiled in an area designated by the PROJECT ENGINEER or designee within two (2) miles of the work site.

I.) Method of Measurement: The method of measurement for concrete sidewalk shall be in square yards. No deduction will be made for the area occupied by ornamental trees left within the area of the sidewalk. No deduction will be made for any areas occupied by manholes, inlets or other drainage structures or by public utility appurtenances with the normal sidewalk.

J.) Bid Items and Basis of Payment: The quantity determined to be paid for shall be at the contract unit price per square yard for concrete sidewalk, which price and payment shall be full compensation for all the work specified in this section, including the removal and disposal o the existing sidewalk, completed and accepted.

Payment shall be made under items: