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Concrete Sitework

Concrete Sitework

(Section 02513)

PART 1 GENERAL

A. Contractor shall provide all materials, labor, tools, equipment, fees, permits, transportation and other items required to furnish and install concrete sitework as indicated or as required to accomplish Work of other sections of these specifications. All concrete sitework shall be in accordance with applicable regulations and as specified herein.

B. Concrete sitework includes, but is not limited to the following:

     1. Form Construction

     2. Concrete Materials

     3. Placing Concrete

     4. Sidewalk and Curb and Gutter Joints

     5. Hot and Cold Weather Concreting

     6. Finishing

     7. Curing

     8. Testing, Clean-up and Protection

1.02 RELATED WORK

A. Section 02220 - Excavating, Backfilling and Compaction

     1. Materials and compaction requirements for subgrades beneath paved areas.

1.03 REFERENCES

A. The applicable provisions of the latest editions of the References listed below shall govern the Work covered under this Section, unless there is a conflict between said References and the requirements of this Section. In the case of such a conflict, the requirements of this Section shall apply.

B. American National Standards Institute (ANSI)

C. The American Concrete Institute (ACI)

D. American Society for Testing and Materials (ASTM)


E. American Association of State Highway and Transportation Officials (AASHTO)

F. Midvale City Corporation Standard Construction Details

1.04 SUBMITTALS

A. Submit evidence of materials conformance with applicable requirements as well as these specifications.

B. Submittals generally include, but are not limited to the following:

     1. A mix design shall be submitted to Engineer at least two weeks prior to commencement of the work.

     2. Submit construction, expansion and contraction joint layout plan for review and approval at least 14 days prior to start of concreting.

     3. Submit manufacturer's data for all materials used.

     4. Provide weight tickets to owner's representative for all ready-mixed concrete at the time of delivery to the site.

1.05 QUALITY ASSURANCE

A. Qualifications of Workmen:

     1. Use workmen thoroughly trained and experienced in placing and finishing the types of concrete specified. Provide a minimum of one ACI certified flatwork finished with each concrete finishing crew.

B. Comply with federal, state and local codes and regulations.

C. Comply with hot or cold weather requirements when applicable.

D. Two (2) Year Written Guarantee.

     1. Provide two year written guarantee to the Owner, in form approved by the Architect to promptly remove and/or repair defective concrete (cracking, spalling, pitting or honeycombing) as directed by Engineer and at Contractor's expense. New replacement work shall carry a similar new two year written guarantee. Guarantee shall start from Date of Substantial Completion.

1.06 DELIVERY, STORAGE AND HANDLING

A. Contractor shall be responsible for proper storage of all equipment and materials to be provided as part of this specification in accordance with the manufacturer's recommendations and shall be responsible for security and proper handling of such equipment and materials at the project site.

B. Any materials lost, stolen, or damaged prior to Owner's final acceptance are to be replaced or repaired to the Owner's satisfaction by the Contractor at no additional cost to the Owner.

C. Ready mixed concrete: Concrete shall be mixed only in such quantities as are required for immediate use. The maximum allowable time between charging of the material in the mixing drum and final placing shall be ninety minutes for air temperatures below 80 F and sixty minutes for temperatures above 80 F. Concrete not placed within these time limits, or if an initial set has developed shall not be used. Tempering concrete by adding water or by other means will not be permitted.

1.07 PROJECT CONDITIONS

Not Used


PART 2 PRODUCTS

2.01 MANUFACTURERS

2.02 PORTLAND CEMENT CONCRETE MATERIALS

A. Cement:

     1. Portland cement shall be Type II, complying with ASTM C150 - Standard Specification for Portland Cement.

B. Coarse Aggregates:

     1. Shall conform to ASTM C33 - Standard Specification for Concrete Aggregates.

     2. Coarse aggregate shall be graded within the following limits:

          Sieve % Passing
          1-1/2" 100
          1" 95 - 100
          1/2" 25 - 60
          No. 4 10 - 40

     3. Coarse aggregate shall consist of gravel, crushed slag, or crushed stone, composed of hard, strong and durable particles, free of injurious coatings.

C. Fine aggregate:

     1. Shall conform to ASTM C33.

     2. Fine aggregate shall consist of natural sand, composed of hard, strong and durable particles.

     3. Fine aggregate shall be uniformly graded from coarse to fine within the following gradation:

          Sieve % Passing 3/8" 100
          No. 4 95 100
          No. 8 80-100
          No. 16 50 85
          No. 30 25-60
          No. 50 10 30
          No. 100 2 10

D. Water:

     1. Water used in washing aggregate and mixing concrete shall be of a potable quality clean and free from oil, acid, salt, injurious amounts of alkali, organic matter or other deleterious substances.

E. Admixtures:

     1. No admixture will be permitted to be used in Portland cement concrete except for an air entraining agent, and a concrete coloring agent.

F. Air entraining agent:

     1. Shall be used in all concrete.

     2. The agent shall conform to ASTM Designation C260 - Standard Specification for Air-Entraining Admixtures for Concrete.

     3. Shall be added at the mixer.

G. Concrete curing compound:

     1. Liquid membrane curing compound shall comply with ASTM Designation C309 - Standard Specification for Liquid Membrane-Forming Compounds for Curing Concrete, Type II Class A. Moisture loss not more than 0.055 gr./sq. cm when applied at 200 sq. ft./gal.

2.03 PORTLAND CEMENT CONCRETE MIX

A. Portland Cement Concrete shall consist of a mixture of water, Portland Cement, fine and coarse aggregates, and an air entraining agent.

B. The proportions of the concrete materials shall produce a mixture that will work readily into corners and angles of forms and around reinforcing steel.

C. The methods of measuring concrete materials shall permit proportions to be accurately controlled and easily checked. Measurement of materials for ready mixed concrete shall conform to ASTM C94 - Standard Specification for Ready-Mixed Concrete.

D. Concrete mix design:

     Intended Use: Storm drainage, curbs, walks and driveways.
     Coarse Aggregate Size: 1"
     Minimum Cement Content: 6.5 sacks/CY
     Minimum 28 Day Compressive Strength: 4000 psi
     Minimum 28 Day Flexural Strength: 550 psi
     Required Slump: 2.5 - 4 inches
     Air Entrainment 5 - 6.5 percent

E. The contractor shall be responsible for the mix design.

2.04 JOINT MATERIALS

A. Filler material shall be pre-formed, non-extruding resilient type complying with ASTM D-544 of thickness to fill joint.

B. Joint sealant shall be polyurethane based, self leveling, one part elastomeric sealant complying with FS-TT-S00230 Class A Type I. (unless Type II is recommended by manufacturer for application). Select marketing materials of sufficient strength and hardness to withstand stiletto heel traffic without damage or deterioration.

2.05 CONCRETE REINFORCEMENT

A. Reinforcing steel:

     1. All reinforcing bare material used for reinforcement of concrete shall be intermediate Grade 60 steel conforming to the requirements of ASTM A-615.

     2. All rods shall be deformed and round.

     3. All reinforcement shall be uncoated, free from rust, scale, form oil, etc.

     4. Welded wire fabric for concrete reinforcement shall conform to ASTM A-185.

B. Accessories:

     1. All accessories, including such items as chairs, spacers, saddles, etc., shall be of steel formed in such a manner and with sufficient strength to perform the intended functions. Chairs, spacers, saddles, etc., which are set in contact with forms, are to be galvanized or provided with plastic tips or coating to prevent rust spots on finish concrete surface.

C. Wire:

     1. All tying steel shall not be less than 18 gage annealed iron lacing wire. All wire tie ends shall point away from forms.

 


D. Fibermesh:

     1. All flatwork to have fibermesh.

2.06 FORM MATERIALS

A. Forms shall be of suitable material and of a type, size, shape, quality, and strength to insure construction as designed.

B. Metal forms for exposed surfaces may be used when all bolt and rivet holes are countersunk so that a plane, smooth surface of the desired contour is obtained.

C. Rough lumber may be used for forming surfaces that will be covered by earth in the finished structure.

D. Forms for all surfaces that will not be completely enclosed or hidden below the permanent surface of the ground shall be made of surfaced lumber, or material which will provide a surface at least equal to surfaced lumber or plywood.

E. All lumber shall be free from knotholes, loose knots, cracks, splits, warps, or other defects affecting the strength or appearance of the finished work. Any lumber or material which becomes badly checked or warped, prior to placing concrete, shall not be used.

F. All forms shall be free of bulge and warp, and shall be cleaned thoroughly before being used.

2.07 EQUIPMENT

A. The use of Power Screed equipment will be required for all concrete pavement work.

B. Slip-Form Paver:

     1. At the option of the Contractor, and with the approval of the Engineer, concrete pavement may be constructed by the use of slip-form paving equipment. The slip-form paver shall consist of a self-propelled, self-powered machine capable of spreading, vibrating, tamping, striking-off, and shaping the concrete to the desired line, grade, and thickness in one continuous passage.

     2. The slip-form paver shall be equipped with internal-type vibrators meeting the following requirements:

          Eccentric Diameter 1-7/8 inch

          Frequency 9,500 vibrations per minute (min)

           Spacing 24 inches maximum when mounted transversely; 18 inches when mounted longitudinally

     3. The vibrators shall be operated horizontally at the height of the midpoint of the concrete slab and shall be mounted so they will maintain this position. The vibrators may be mounted in a traverse or longitudinal position.

     4. Each vibrator shall be equipped with an indicator light or other electrical device that will indicate whether or not the vibrator is operating. The lights or other devices shall be mounted on the paving machine so they can be easily seen by the operator and the inspector. If the lights or other devices show that a vibrator or vibrators are not operating properly, the paving operations shall be stopped immediately. Paving operations shall not be resumed until the faulty vibrator or vibrators have been repaired or replaced.

     5. The paver shall be capable of providing a continuous deposit of concrete with a minimum of starting and stopping. Trailing forms shall be of a sufficient length to leave a smooth, straight, vertical edge or a keyed longitudinal construction joint of the shape shown on the Drawings. The trailing forms shall be held in position by suitable devices sufficiently rigid to prevent spreading of the forms under the weight of the concrete and finishing operations.

PART 3 EXECUTION

3.01 EXAMINATION

A. Coordinate layout and installation of concrete sitework with other construction elements to ensure adequate headroom, working clearance, and access.

B. Examine surfaces to receive concrete sitework for compliance with installation tolerances and other conditions affecting performance of the paving system. Do not proceed with installation until unsatisfactory conditions have been corrected.

3.02 METHODS OR PROCEDURES

A. Preparation

     1. Remove all wood scraps, ice, snow, frost and debris from the areas in which concretewill be placed.

     2. Thoroughly clean the areas to ensure proper placement and bonding of concrete.

     3. All reinforcement shall be free from loose mill scale, loose or thick rust, dirt, paint, oil, or grease, and shall present a clean surface.

     4. Thoroughly wet the forms (except in freezing weather), or oil them and remove all standing water.

     5. Thoroughly clean all transporting and handling equipment.

     6. Notify the Owner at least 24 hours before placing concrete.
 


     7. Obtain the Architect/Engineer's approval of location of all construction joints and control joints in the Work prior to start of concrete placement.

     8. Erect and maintain suitable barriers to protect the finished surface. Any section damaged from traffic or other causes occurring prior to its official acceptance, shall be repaired or replaced by the Contractor at his own expense in a manner satisfactory to the Architect/Engineer.

B. Hot Weather Concreting

     1. Hot weather is defined as any combination of high air temperature, low relative humidity, and wind velocity tending to impair the quality of fresh or hardened concrete or otherwise resulting in abnormal properties. Hot weather concreting shall follow the guidelines of ACI 305R, latest edition.

     2. Undesirable hot weather effects on concrete in the plastic state may include:

          a. Increased water demand.

          b. Increased rate of slump loss and corresponding tendency to add water at job site.

          c. Increased rate of setting resulting in greater difficulty with handling, finishing, and curing, and increasing the possibility of cold joints.

          d. Increased tendency for plastic cracking.

          e. Increased difficulty in controlling entrained air content.

3. Undesirable hot weather effects on concrete in the hardened state may include:

          a. Decreased strength resulting from higher water demand and increased temperature level.

          b. Increased tendency for drying shrinkage and differential thermal cracking.

          c. Decreased durability.

          d. Decreased uniformity of surface appearance.

     4. Placing and curing:

          a. Concrete shall be handled and transported with a minimum of segregation and slump loss. Concrete temperature at time of placement shall be such that the rate of evaporation for the weather conditions shall not cause cracking.


          b. The aggregate shall be cooled by frequent spraying in such a manner as to utilize the cooling effect of evaporation. The placement schedule shall be arranged, as approved, in such a manner as to provide time for the temperature of the previously placed course to begin to recede. The mixing water shall be the coolest available at the site insofar as is practicable.

          c. Concrete shall be placed where it is to remain.

          d. Concrete shall be placed in layers shallow enough to assure vibration well into the layer below.

          e. Surfaces exposed to the drying wind shall be covered up immediately after finishing with polyethylene sheets and be water cured continuously as soon as the concrete has set up. Curing compounds, in lieu of water, may be used.

          f. Joints be made on sound, clean concrete.

          g. Finishing operations and their timing be shall be guided only by the readiness of the concrete for them, and nothing else.

          h. Curing shall be conducted in such a manner that at no time during the prescribed period will the concrete lack ample moisture and temperature control. Facilities must be ready to protect promptly all exposed surfaces from drying. All work determined by Engineer to be damaged from hot weather shall be removed and replaced at no cost to Owner.

          i. All materials and workmanship required to meet the hot weather requirements shall be supplied at the Contractor's own expense.

C. Cold Weather Concreting

     1. Cold weather is generally defined as a period when for more than 3 successive days the mean daily temperature drops below 40 F. When temperatures above 50 F occur during more than half of any 24-hour period, the weather should no longer be regarded as "cold". The times and temperatures given for various conditions and situations are not exact values and should not be used as such. Weather conditions are variable and common sense must be used to protect the concrete. Cold weather concreting shall follow the guidelines of ACI 306R, latest edition.

     2. All materials and workmanship required to meet the cold weather requirements shall be supplied at the Contractor's own expense.

          a. Preparation:

               i. When specific written authorization is given to permit concreting operations at temperatures below those specified herein, arrangements for covering, insulating, housing, or heating materials and/or newly placed concrete should be made in advance of placement and should be adequate to achieve the temperature and moisture conditions recommended herein in all parts of the concrete. All equipment and materials necessary should be at the work site before the first frosts are likely to occur, not after concrete has been placed and its temperature begins to approach the freezing point.         

          b. Concrete Temperature:

               i. The temperature of the concrete as mixed shall be maintained as shown in the following table:

Air Temperature Minimum Concrete Temperature as mixed

Above 30 F 60 F

0 F to 30 F 65 F

Below 0 F 70 F

               ii. The minimum concrete temperature as placed and maintained shall be 55 F.

          c. Placement and protection:

               i. During placement of concrete, tarpaulins, or other readily movable coverings supported on horses or framework should follow closely the placing of the concrete so that only a few feet of concrete are exposed to outside air at any time.

               ii. The housing, covering, or other protection used in curing shall remain intact at least 24 hours after artificial heating is discontinued.

               iii. All concrete placed in forms shall have a temperature between 55 and 70 after placement. Adequate means shall be provided for maintaining the surrounding air at 60 F for at least seventy-two (72) hours after placing and at no less than 40 F for an additional four days. All methods and equipment for heating shall be subject to approval. Insulating blankets shall be used when required to maintain a satisfactory temperature during the curing period.

               iv. No dependence shall be placed on salt or other chemicals for the prevention of freezing.

               v. If heating or other protective measures need to be taken to prevent concrete from freezing, the concrete may require special curing methods to prevent rapid drying, as described in ACI 306R-78.

               vi. Salt or other chemicals shall not be used for prevention of freezing.

3.03 INSTALLATION

A. Form Construction

     1. Forms shall be constructed so that the finished concrete shall be of the form and dimensions shown on the plans and true to line and grade, and sufficiently rigid to resist deflection. Design of form work and removal of forms and shores are to conform to ACI 381. The responsibility for their adequacy shall rest with the contractor.



     2. All forms shall be mortar tight and designed and constructed so that they may be removed without injuring the concrete.

     3. If, at any stage of the work, during or after placing the concrete, the forms sag or bulge to such an extent as to allow concrete to fall below the elevation shown on the plans, or outside the true line of the form, the concrete affected shall be removed.

     4. No concrete may be deposited against the earth as a side form.

B. Placing Steel Reinforcement

     1. Reinforcing bars shall be accurately placed as shown on the plans and shall be firmly and securely held in position in accordance with the "Manual of Standard Practice" of the Concrete Reinforcing Steel Institute, using concrete or metal chairs, spacers, metal hangers, supporting wires and other appropriate devices of sufficient strength to resist crushing under full load. Metal chairs which extend to the surface of the concrete (except where shown on the plans) and wooden supports, shall not be used.

     2. Placing bars on layers of fresh concrete as the work progresses and adjusting bars during the placing of concrete will not be permitted.

     3. Tack welding of reinforcing bars in place shall not be allowed.

     4. Splicing:

          a. Splices of bars shall be made only where shown on the Drawings or as approved by the Owner.

          b. Where bars are spliced, they shall be lapped at least 30 diameters, unless otherwise shown on the plans.

          c. Splicing shall be accomplished by placing the bars in contact with each other and wiring them together.

     5. Bending reinforcement:

          a. Bends and hooks in bars shall be made in the manner prescribed in the "Manual of Standard Practice" of the Concrete Reinforcing Steel Institute.

          b. Bars shall not be bent or straightened in a manner which will injure the material.

          c. Bars with kinks or unspecified bends shall not be used.

C. Placing Concrete

     1. Convey concrete from mixer to place of final deposit by methods that will prevent separation and loss of materials.

          a. The free fall of concrete from the end of the spout or chute, or from a transporting vehicle, shall not exceed 10 feet for thin walls (10 inches or less in thickness) nor more than 5 feet for other types of construction.

          b. When the distance through which concrete must be dropped vertically exceeds the maximums specified above, a tremie or flexible metal spout shall be used. Flexible metal spouts having sufficient strength to hold the weight of the concrete shall be composed of conical sections not more than 3 feet long, with the diameter of the outlet and taper of the various sections such that the concrete will fill the outlet and be retarded in its flow.

          c. Chutes, troughs, or pipes used as aids in placing concrete shall be arranged and used so that the ingredients of the concrete will not be separated. Chutes and troughs shall be of metal or metal lined. When steep slopes are necessary, the chutes shall be equipped with baffle boards or a reversed section at the outlet. Open troughs and chutes shall extend, if necessary, down inside the forms or through holes left in the forms; or the ends of such chutes shall terminate in vertical downspouts.

     2. Place concrete as dry as possible consistent with good workmanship, never exceeding the maximum specified slump.

     3. On arrival at the job site, adding water to the mix shall not be allowed.

     4. Place concrete at such a rate that concrete is at all times plastic and flows readily between bare bars.

     5. When placing is once started, carry it on as a continuous operation until placement of the section is complete.

     6. Do not pour a greater area at one time than can be properly finished without checking; this is particularly important during hot or dry weather.

     7. Thoroughly consolidate by suitable means during placement, working it around all embedded fixtures and into corners of forms.

     8. No water shall be added to the concrete surface behind the screed. Addition of water to the concrete surface shall be cause for shutting down the placement operations and rejection of any suspect work.

     9. Do not use re-tempered concrete that has been contaminated by foreign materials.

     10. Struts, stays, and braces serving temporarily to hold the forms in correct shape and alignment, pending the placing of concrete at their locations, shall be removed when the concrete placing has reached the elevation rendering their service unnecessary. These temporary members shall be entirely removed from the forms.

     11. Unless necessary materials and equipment are readily available to adequately protect the concrete in place, placing operations may be postponed by the Engineer when, in his opinion, impending conditions may result in rainfall or low temperatures which will impair the quality of the finished work. The Contractor shall pay for all delay related costs resulting from such postponements including costs for removing and replacing damaged concrete. In case rainfall should occur after placing operations are started, provide ample covering to protect the work.

     12. Whenever it is necessary to continue the mixing, placing, and finishing of concrete after daylight hours, the site of the work shall be adequately lighted so that all operations are plainly visible. Every effort shall be made to enable finishing to be done in daylight.

     13. Except by specific written authorization from the Architect/Engineer, concreting operations shall not be continued when a descending air temperature, in the shade and away from artificial heat, falls below 40 F, nor shall operations be resumed until ascending air temperature reaches 35 F. However, such authorization shall in no way relieve the Contractor of responsibility for proper results. Any concrete injured by frost action shall be removed and replaced at the Contractor's expense. All materials and workmanship required to meet the cold weather requirements shall be supplied at the Contractor's own expense.

     14. The concrete shall be distributed to such depth and width that the plan thickness and grade will be obtained for the entire width of the pass. The spread concrete shall be vibrated, screened, and tamped by mechanical means. No manual screeding or tamping will be allowed, except in those cases where the use of a mechanical tamper and screeder would be obviously impracticable. Any delay in excess of fifteen minutes in vibrating, screeding and tamping shall constitute cause for shutting down the operation until the difficulties are corrected.

     15. Discharge of mixed concrete from hauling equipment and processing by the initial power laydown machine or power screed shall be accomplished within sixty minutes after introduction of the mixing water to the cement and aggregates.

     16. The concrete shall be deposited in such a manner as to require as little rehandling as possible. It shall be thoroughly vibrated against and along the faces of the forms. Necessary hand spreading shall be done with shovels, not with rakes. Workmen shall not be allowed to walk in the newly placed concrete with boots coated with earth.

D Sidewalk and Curb and Gutter Joints

     1. Locate joints as specified herein or as required on the plans.

     2. Make all joints perpendicular and straight.

     3. Joints for concrete structures that were removed or damaged as a result of construction under this contract shall match joints in the remaining original structure.

     4. Expansion Joints

          a. Sidewalk: Expansion joints one half inch in thickness shall be constructed every 40-50 feet by using premolded expansion joint material. Also, expansion joints shall be placed where the new sidewalk meets existing sidewalks, fixed objects and where it meets the curb at all handicap ramps. No dowel bars shall be required at the joints.

          b. Curb & gutter: Expansion joints, one half inch in thickness, shall be constructed every 40-50 feet and at changes in direction by using premolded expansion joint filler. For both formed and slipformed curb and gutter, joint filler shall also be placed between the curb and/or gutter and storm drainage structures.

          c. Joint sealant will be installed over all expansion joints. Provide bond breaker and install per manufacturer specifications.

     5. Contraction Joints

          a. Sidewalk: Contraction joints shall be constructed at intervals equal to the width of the walk by cutting into the fresh concrete to a minimum depth of 1/4 of the thickness of the concrete to create a plane of weakness. The edges of tooled joints shall be rounded to provide a neat, workmanlike appearance.

          b. Curb: Contraction joints shall be constructed every ten feet as shown on the plans by using steel templates not less than one eighth inch nor more than three-sixteenth inch in thickness. The templates shall be removed as soon as the concrete has set sufficiently to hold its shape. Where curbs and curb and gutter are placed by slipform methods, the contraction joints every ten feet may be provided by cutting into the fresh concrete to a minimum depth of 1 1/2 inches to create a plane of weakness. The edges of such joints shall be rounded to provide a neat workmanlike appearance.

     6. Immediately after the forms are removed, the expansion joints shall be inspected carefully. Any concrete or mortar that has sealed across the joint shall be cut neatly and removed.

E. Finishing

     1. The surface of the concrete shall be finished smooth and true to grade by float. The finishing shall commence immediately after the concrete is placed and shall progress at a rate equal to the progress of the paving operation. Any delay in excess of thirty minutes in performing the preliminary finishing shall constitute cause for shutting down the mixing operations until the finishing is resumed.

     2. Hand methods of strike-off and consolidation will only be permitted when the width of pavement to be constructed is less than 10 feet or at rounded intersections where the use of machine finishing is impracticable.

     3. While the concrete is still plastic, the entire slab surface will be tested by the Contractor for trueness with an accurate 10 foot straightedge. Any depressions that are found shall be immediately filled with freshly mixed concrete, struck-off, consolidated and refinished. High spots shall also be struck-off and refinished.

     4. In advance of the curing operations the pavement shall be textured by brooming. Initial brooming operation shall permit Owner to review texture and recommend modifications, if any.

     5. Finished Surface:

          a. The finished surface shall be true to grade and cross section, free from ruts, humps, depression or other irregularities. The surface shall not deviate from line and grade by more than 1/8 inch, plus or minus, in 10 feet. The determination of compliance with smoothness may be made with a straightedge or string line at the option of the Engineer. Any irregularities that may be found shall be corrected at the expense of the Contractor by means of a suitable grinding and grooving tool.

          b. The grinding tool shall consist of a machine equipped with cutting wheels mounted on a horizontal shaft. The grinding action shall be conducted parallel to the centerline. Grinding operations shall be deferred, as directed by the Engineer, whenever tearing of aggregate with the surface occurs and shall not be resumed until the concrete has hardened sufficiently to avoid tearing.

          c. The finished surface across contact joints shall not deviate from a straight line by more than 1/8 inch (vertically) in 12 inches when tested with a straightedge. The Contractor shall take the necessary precautions to prevent slumping of the edge of the concrete at contact joints.

          d. Line and grade control: The Contractor shall establish references at reasonable intervals, usually at subgrade elevation, for line and grade control of the placing operations. The Contractor shall furnish, place, and maintain such supports, wire devices, and materials as may be required to provide continuous line and grade reference controls to the placing machine, trimmers or paver.

          e. At least one ACI certified concrete finisher to be on crew at all times.

3.04 PROTECTION

A. The Contractor shall protect the concrete against all damage and markings. Barricades shall be placed at the proper locations to prevent traffic from using the pavement.

B. When it is necessary to provide for traffic crossing the concrete, the Contractor shall, at his expense, construct suitable substantial crossings to bridge over the concrete satisfactory to the Architects/Engineer.



C. Newly placed concrete shall be protected from damage by rain, snow and hail. Placing operations shall be stopped when rain is threatening, as determined by the Owner. The Contractor shall have available on the project enough material to cover the plastic concrete to prevent damage by rain, snow or hail. Any concrete damage due to rain, snow or hail shall be removed by the Contractor at his expense.

D. No traffic or Contractor's hauling equipment will be permitted on the concrete until the concrete has developed a modules of rapture of 450 psi, when tested in accordance with AASHTO Designations T-97 but, in no case before ten calendar days have elapsed after the concrete has been placed. The concrete shall be cleaned and all joints shall be sealed and trimmed as previously specified before traffic is allowed to use the pavement.

E. Curing

     1. Protect the concrete from the effects of weather in accordance with HOT WEATHER CONCRETING AND COLD WEATHER CONCRETING in this section.

     2. Water for curing shall be as specified in PART 2 - PRODUCTS.

     3. Other curing requirements may be required in individual Specifications Sections.

     4. Membrane curing compound method:

          a. Surface of newly placed or exposed concrete shall be kept moist or wet until the curing compound is applied. The curing compound shall be applied immediately after all patching or surface finishing has been completed.

          b. The curing compound shall be delivered to the work in ready-mixed form. At the time of use, the compound shall be in a thoroughly mixed condition with the pigment uniformly dispersed throughout the vehicle. The compound shall not be diluted or altered in any manner.

          c. Curing compound that has become chilled to such an extent that it is too viscous for satisfactory application shall be warmed to a temperature not exceeding 100 F, unless otherwise specified by manufacturer's recommendations.

          d. The curing compound shall be applied to the exposed surface at a uniform rate of 1 gallon per 100 square feet of area, unless otherwise required by manufacturer's recommendations.

          e. In the event that the application of curing compound is delayed, the application of water as provided in this section shall be started immediately and shall be continued until application of the compound is resumed or started.

 

3.05 TESTING

A. Testing will be provided by an independent testing laboratory employed by the Owner. Refer to individual Specifications Sections for other Field Quality Control requirements.

B. Concrete sampled from a concrete pump shall be sampled from the hose after all of the priming grout has been wasted. The end of the hose shall be placed in a horizontal position before the concrete is discharged into the sampling pan. The concrete shall not be allowed to fall into the sampling pan.

C. The Contractor, at his expense, shall furnish the concrete required for testing.

D. Strength, slump and air tests shall be taken in accordance with the following unless otherwise specified in individual Specifications Sections:

     1. Strength, slump and air tests may be taken in accordance with the placement rate per day as shown below:

                                                                                                                        Compress.
          Rate/day (C.Y.)                            Air                       Slump                       Strength

          0-8                                               1                            1                           Optional
          8-20                                             1                            1                            1
          For each 20 C.Y.
          or fraction thereof                          1                            1                            1

     2. Compressive strength test specimens shall be made and cured in accordance with ASTM C31 - Standard Practice for Making and Curing Concrete Test Specimens in the Field; Specimens shall be tested in accordance with ASTM C39 - Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens.

          a. Three specimens shall be made by the Engineer for each test, and these shall be broken at 7 and at 28 days, with one held in reserve.

          b. At least one test (3 specimens) shall be made for each class of concrete or each poured during one day.

     3. Flexural strength test specimens shall be prepared in accordance with AASHTO Designation T-23 and tested for flexural strength in accordance with AASHTO Designation T-97.

          a. Four specimens shall be made by the Engineer for each test, and one shall be broken at 3, one at 7 and 2 at 28 days, with one held in reserve.

          b. At least one test (4 specimens) shall be made for each class of concrete poured during one day.

     4. If an air test does not meet the specification, a second air test shall be made immediately upon the same load. The concrete shall be accepted if the second air test meets the specification or rejected and removed from the project if the second air test does not meet the specification.

     5. Slump and air tests shall be made in accordance with ASTM C143 - Standard Test Method for Slump of Hydraulic Cement Concrete and C231 - Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method, respectively.

     6. The maximum allowable time between charging of the material in the mixing drum and final placing shall be ninety minutes for air temperatures below 80 F and sixty minutes for temperatures above 80 F. Concrete not placed within these time limits, or if an initial set has developed shall not be used. Tempering concrete by adding water or by other means will not be permitted.

     7. If a compressive strength test is below the required specified strength, the Engineer shall immediately notify the Contractor or his authorized representative.

     8. All costs incurred in resampling and retesting shall be paid by the Contractor if the retested strength is below the specified strength, and shall be assumed by the Owner if the retested strength is above the specified strength.

3.06 CLEANING

A. Contractor shall remove all forms, excess materials, debris and other items upon completion of concrete sitework.

B. All damage to concrete sitework prior to Owner's acceptance shall be repaired or replaced to Owner's satisfaction at the expense of the Contractor.