- 403 - SECTION 603 -- CO NCRETE PAVEMENT
603.01 Description
1.This work shall consist of furnishing all materials and constructing Portland cement concrete pavements, approach slabs, and headers. They are to be constructed on a prepared subgrade, modified subgrade or foundation course.
603.02 Material Requirements
1.The concrete class for pavements, headers and bridge approach slabs shall be as specified in the contract.
2.All materials shall be furnished by the Contractor and shall conform to the requirements of the Sections shown in Table 603.01. Table 603.01 Material Requirements Applicable Materials Section Fly Ash ........................................................... 1008 Admixtures ..................................................... 1007 Curing Materi als ............................................. 101 0, 1011, 1012, 1013 Aggregates .................................................... 1033 Deformed Metal Join t Material ....................... 1027 Dowel Bars .................................................... 1022 Joint Sealing Filler .......................................... 1014 Portland Cement Concrete ............................ 1002 Preformed Join t Filler ..................................... 1015 Preformed Polychloroprene Elastomeric Joint Se als .................................................. 1016 Reinforcing Steel ............................................ 1020, 1021, 1024 Tie Bars ......................................................... 1020 Water ............................................................. 1005
603.03 Construction Methods
1.General Preparation:
a.The Contractor shall pre pare the subgrade as described in Section 302 or the contract.
b.The foundation course shall be constructed in accordance with the requirements of Secti on 307 or in the contract.
c.In no case shall concrete be placed upon an unstable or frozen subgrade or foundation course.
2.Slip-Form Preparation:
a.Grade control shall be maintained by the Contractor. (1) Conventional Stringline shall be installed utilizing the construction staking provided by the Department or by the Contractor if Contractor Staking is required.
2.Stringless machine grade control may be utilized, provided that the Contractor prep ares a digital terrain model (DTM) to a system specifically designed to control the paving equipment. The Contractor shall provide elevations from the DTM at key locations selected by the Engineer,
603.03 Concrete Pavement
- 404 - such as but not limited to, inlets, bridge approaches, intersections, and superelevations.
3.Fixed Form Preparation:
a.Form depth shall be equal to the pavement thickness. Wood or metal forms of the proper radii shall be used for curves having radii of less than 100 feet (30 m).
b.The forms shall be neatly and tightly joined, and then securely pinned and staked to line and grade.
4.General Placing Concrete:
a.The concrete shall be spread to the required depth and cross section, consolidated, leveled, and fi nished to the grade shown in the contract.
b.The base material shall be uniformly moistened prior to concrete placement as directed by the Engineer.
c.To place concrete at ni ght, the Contractor must request permission from the Engineer 24 hours in advance of placement.
d.Operations shall not be star ted until the ascending ambient air temperature reaches 40°F (5°C) or when a forecasted descending temperature is expected to fall below 40°F (5°C) during placement. Mixing and placing operations shall be discontinued when the descending ambient air temperature reaches 40°F (5°C).
e.Placement authorized for ambi ent air temperatures below 40°F (5°C) shall be as described in Subsection 704.03. Any concrete damaged by freezing shall be rejected.
f.Portland cement concrete shall be handled and placed with the following maximum limits:
1.Concrete shall be consolidated, leveled, and finished within 30 minutes of it being placed on the grade. (2). Concrete shall not be k ept in non-agitat ing trucks (i.e., dump trucks) more than 30 minutes.
3.Concrete shall not be kept in an agitating truck more than 90 minutes.
4.A transverse construction joint shall be installed whenever work stops for more than 30 minutes. However, no section's length shall be less than 10 feet (3 m).
g.Cracks which form in the concrete pavement panels between joints shall be replaced or repaired as directed by the Engineer. No payment will be made for this work.
h.The Contractor may use a machine to place the longitudinal tie bars in lieu of tie bar pins shown in t he contract. It must be located in the paving train so as to place tie bars prior to the placement of the wire mesh on reinforced concrete pavement, or prio r to the passage of the first finishing machine on non-reinforced concrete pavement.
i.Finished concrete shall be of uniform density with no segregation, honeycombing, or large voids. Concrete Pavement 603.03 - 405 - 5. Slip-Form Placing Concrete:
a.All concrete shall be consolidated by internal vibration with transverse vibrating units or a series of longitudinal vibrating units.
b.The concrete float finisher shall be directly attached to the paver.
6.Doweled Concrete Pavement
a.Dowel bars shall be placed at mid-depth of the slab, parallel to the finished surface of the slab, and paralle l to the centerline of the roadway.
b.Dowel bars may be placed by use of either baskets or mechanical inserters.
c.The dowel bars shall be placed within a tolerance of 1/4 inch (6 mm) in both the horizontal and vertical planes. The Engineer may elect to dig into the plastic concrete to verify dowel bar orientation and location. The subsequent hole shall be repaired by the Contractor at no additional expense to the Department.
d.Dowel bars for transverse joints furnished in approved assemblies shall be suitable for the joint layout as shown in the contract. The assemblies shall be dipped in an asphaltic bond breaker found on the Approved Products List prior to delivery to the work site.
1.When basket assemblies are used, the baskets shall be placed at all transverse joints where doweled concrete is required, and shall be securely pinned to the grade to prevent any movement during the paving operation. Pins shall be placed at a maximum distance of three feet (1 m) apart and shall be a minimum of 12 inches (300 mm) in length. All lateral support braces shall not be cut after the baskets are secured and prior to placing the concrete.
2.Assemblies that are damaged prior to placement shall not be used. Assemblies damaged after placement shall be replaced prior to paving.
e.Transverse Joints for doweled concrete pavement shall be constructed perpendicular to the roadwa y on 16 foot 6 inch (5 m) centers.
f.For areas with pavement widening, dowel baskets shall be placed in all transverse joints which are 6 feet (1.8 m) or wider.
g.Transverse cracks which form in the concrete pavement panels between load transfer joints shall be replaced or repaired as directed by the Engineer. No payment will be made for this work.
7.Placing Reinforcing Steel: a. Welded steel wire fabric shall be installed on a level and consolidated layer of concrete whose top surface is at the elevation specified for the reinforcing metal.
1.Welded steel wire fabric shall be lapped at least 1 foot (300 mm).
2.The welded steel wire fabric shall be tied together at all laps.
3.The spacing between the ties of longitudinal laps shall not exceed 2 feet (600 mm).
603.03 Concrete Pavement
- 406 - (4) The transverse laps shall be tied with a minimum of 3 ties per lane width. (5). Any portion of the bottom layer of concrete that has been placed more than 30 minutes without being covered with the top layer shall be rejected.
b.Placing Tie Bars: (1) The tie bars shall be placed as shown in the plans and in Table 603.02. Table 603.02 TIE BARS FOR LONGITUDINAL JOINTS Slab Thickness Bar Size* Bar Spacing 5” (125 mm) 6-10” (150-250 mm) More Than 10” (250 mm) #4 (#13) #5 (#16) #6 (#19) 24” (610 mm) 33” (840 mm) 33” (840 mm) *#5 bars will be used in place of #6 bent bars that must be straightened.
2.The contractor may use a machine or jig to place tie bars in lieu of tie bar pins.
i.The machine or jig shall be attached to and operated only when the paver to which it is attached is moving. (ii) The machine or jig shall result in placement of tie bars in one quick, continous movement resu lting in maximum contact of plastic concrete around the bar with no void created behind the bar. (iii) Hand placement of tie bars shall not be allowed except in emergencies to complete the day’s concrete placement. (iv) All tie bars, regardless of placement method, shall attain a minimum 12,000 lb pullout strength once the concrete reaches a minimum 3500 psi compressive strength. NDOT may perform pullout testing for verification at any time.
3.Tie bar spacing may vary +/- 4 inches (+/- 100 mm) from the nominal spacing shown. The number of tie bars per 16 feet 6 inch (5 m) panel shall remain constant.
4.No tie bar shall be installed closer than 1/2 the tie bar spacing to a transverse joint.
c.When adjacent pavement lanes are constructed separately, tie bars placed at key-type longitudinal joints may have a 90 degree bend at the center of the bar to facilitate placement.
1.The tie bars shall be bent to a position that is at least 45 degrees to the longitudinal joint.
2.The free end of the bar shall be at least 6 inches (150 mm) horizontally from the dowel bar at the transverse joint.
3.Bars that are loose in their socket must be replaced. Concrete Pavement 603.03 - 407 - (4) All bars that crack or break off shall be replaced by installing tie bars as described in Section 909. Cracked or broken bars shall be replaced at no additional cost to the Department.
5.All deformed tie bars shall be epoxy coated. Epoxy that is damaged by straightening bars to a 45° angle does not need to be repaired.
8.Finishing Concrete Pavement: a. The concrete shall be placed, struck off, screeded and consolidated and finished to the specified finished grade.
1.The concrete-finishing machine shall be power driven and of the transverse-screed type. The finishing machine shall be equipped with two oscillating type transverse screeds. The front screed shall be used for striking off excess concrete to exact grade and crown. The rear screed shall be used for finishing and smoothing. All screeds shall be constructed of steel, capable of being adjusted to the s pecified cross section and shall be of such rigidity as to produce the specif ied crown and cross section. Both the machine and the screeds shall have variable speeds and be independently controlled.
2.Hand methods may be used to finish concrete on narrow or variable width sections where mechanical methods are impractical.
i.After the concrete has been deposited and spread, it shall be vibrated until the concrete is thoroughly consolidated, then struck-off to a uniform height above the specifie d finished grade. It shall then be shaped with heavy vibrating screeds to the described cross section. (ii) If normal vibration is found inadequate to thoroughly consolidate the plastic concrete within and around the dowel basket assemblies, adjustments to the mate rial and/or operations shall be made.
b.The addition of water to the surface of the concrete to assist in finishing operations is not allowed except for unavoidable delays or unusual drying conditions. Fogging the concrete surface may be required to aid finishing. The fog shall be applied as a mist by means of an approved "orchard" sprayer.
1.If it becomes necessary to fog the surface to complete the concrete finishing, all placing operations shall be immediately stopped until the finishers catch up to a point where fogging for finishing is no longer required.
2.An evaporation retardant may be used in addition to fogging. It shall be applied according to the manufacturer’s specifications with approval by the Engineer.
c.The longitudinal surface shall be made smooth and true to the profile with a 10 foot (3 m) straightedge.
1.Straightedges shall be set parallel to centerline and shall be lapped one-half their length in each successive position. High areas shall be removed, depressions filled with fresh concrete, and the concrete consolidated with hand floats.
2.Straightedge testing s hall be continued as necessary until all irregularities have been satisfactorily corrected.
603.03 Concrete Pavement
- 408 - d. Pavement that will not be tined shall be textured by dragging a wet burlap, carpet, or canvas belt over the full width of the surface in a longitudinal direction.
1.A wetted drag used directly behind a slip form paver is allowed.
2.Dampening of this drag material will be accomplished through a uniform, fogging spray pattern. The addition of water to the drag shall not produce unsatisfactory condit ions such as puddling, dripping, or excessive paste on the surface.
3.The drag shall be suspended from a mandrel, or similar device, to insure a uniform texture.
4.The drag shall be lifted fr om the surface of the concrete pavement when the paving train is not in motion for 30 minutes or more and carefully reset before resuming the dragging operations.
5.Drags shall be rinsed or washed as necessary to obtain a uniform surface. Drags that cannot be cleaned shall be replaced.
6.After the final drag finish, hand-formed or machine-formed joints shall be prepared and the concrete over the joints carefully removed. The edges of the pavement along the side forms and joints shall be rounded with an edging tool.
9.Tined Finish. a. When required by the contract or when the posted speed is 40 mph or greater; the Contractor sha ll tine texture the concrete pavement surface using the following methods:
1.Paving shall be tined with a single, full lane width device.
2.The tines shall be of such dimensions as to produce grooves parallel to the centerline of t he road approximately 1/8 inch (3 mm) wide and 1/8 inch (3 mm) deep spaced at 3/4 inch (19 mm) on center. A 2 inch (50 mm) to 3 inch (75 mm) wide strip of pavement surface shall be protected from surface grooving for th e length of and centered along the longitudinal joint.
3.The tining device shall be mechanically operated and shall cover the full pavement width in a single pass at a uniform speed and depth centered on the longitudinal joint. Longitudinal tining shall be accomplished by equipment with horizontal and vertical string line controls to ensure straight grooves.
4.Hand tining will be allowed on irregular areas or areas inaccessible to the tining machine. A tine rake shall be used for hand tining. The use of a corrugated bull float or other device that creates a smooth finish between the grooves will not be permitted.
b.Pavement texture damaged or pavements not textured to the specified requirements shall be textured only after the concrete has attained its designed strength. T he texturing shall be done with diamond grinding equipment specifically designed to grind and texture concrete pavements. The cutting head shall be at least 36 inches (915 mm) wide and capable of producing the depth and spacing indi cated above. This work shall be performed at no additional cost to the Department. Concrete Pavement 603.03 - 409 - 10. Protection:
a.Protection shall be required when concrete is being placed and the ambient air temperature is expected to drop below 35° F (2 C) within 72 hours. The Contractor shall supply min/ max thermometers at 200 ft intervals at no additional cost to the Departmen t. The Contractor shall spread straw, hay, or other suitable blanketing mate rial over the pavement to a sufficient depth to keep the concrete from freezi ng. The blanket material shall be covered with a layer of burlap or plastic sheeting, weighted or anchored to prevent the wind from displacing the insulation. The protection shall be maintained for 10 days or until openi ng strength is obtained, whichever occurs first.
11.General Curing a. Curing aids (liquid membrane , films, sheet, or fabric) shall be installed before plastic shrinkage cracking, "hair-checking", develops.
b.If the rate of evaporation approaches 0.2 lb/SF/h (1.0 kg/m 2/h), the Contractor must notify the Engineer regarding the additional actions that will be taken to prevent plastic shrinkage cracking. The rate of evaporation shall be obtained by using the nomograph in Figure 706.01.
c.The Contractor shall cure concrete pavement by one of the following methods:
1.Curing with liquid membrane-forming compounds:
i.The pavement shall be covered with curing compound within 45 minutes after the pass of the paving machine. (ii) After the final finishing operations, the concrete pavement surface, curbs, and edges with or without tie bars shall be covered with a continuous uniform coating of white-pigmented curing compound as described in Section 1012.
a.Curing compounds shall not be placed on any surface that will be bonded to another concrete surface except for slip- formed pavement. All surfaces of slip-formed pavement shall receive a coat of curing compound.
b.The curing compound shall be applied in 2 applications. The second application shall be made a minimum of 10 feet behind the first application.
c.The total rate of combined applications shall be at a minimum of 1 Gal/100 SF (0.4 L/m2) [0.5 Gal/100 SF (0.2 L/m2) each application] of surface area for tined su rfaces or 1 Gal/150 SF (0.3 L/m2) of surface area for all other finishes.
d.With form paving, the sides of the pavement slab shall be covered with the curing compound within 30 minutes after removal of the forms. (ii) A self-propelled mechanical power sprayer shall be used to apply the curing compound to the concrete pavement. Hand- powered spraying equipment may be employed in an emergency and on narrow or variable width sections where the use of a mechanical power sprayer is impractical.
603.03 Concrete Pavement
- 410 - (a) The mechanical power sprayer shall not ride on the uncured pavement surface.
b.The power sprayer shall be able to cover the entire lane width and thoroughly atomize the curing-compound.
c.If the mechanical power sprayer produces an unsatisfactory result, such as puddles , dripping, or non-uniform application, the paving operation shall be suspended until appropriate changes have been made.
d.The sprayer shall be equipped with a hood to prevent uncontrolled dispersal by the wind. (iii) Damaged curing compound coatings, such as may result during the joint sawing operations, shall be recoated without delay using the same application rate orig inally described. Recoating shall be performed at no additional cost to the Department.
2.Curing with white opaque polyethylene film or white burlap-polyethylene sheets:
i.As soon as practical after the final finishing operations, the top surface of the pave ment shall be covered with a white opaque polyethylene film or white burl ap-polyethylene sheeting conforming to the requirements of Section 1010. Plac ement of the film or sheeting shall be done to avoid damaging the concrete surface. (ii) The film or sheeting shall be placed on the concrete pavement in conformance with the following:
a.The weight of the ro lls of film or sheeting shall be kept off the concrete while placing the material.
b.The material shall cover all exposed horizontal and vertical pavement surfaces.
c.Film or sheeting shall be lapped at least 18 inches (450 mm). The laps shall have a satisfactory anchor placed on them to form a closed joint.
d.The Contractor shall secure the sheeting and/or film so that moisture is held inside the covering to facilitate curing.
e.Any tears or holes in the film or sheeting must be repaired immediately by cementin g patches over the openings.
f.Film or sheeting may be used more than once, provided that it is kept in service able condition by proper repairs, and provided also that it will maintain a watertight covering during the curing period.
g.The concrete pavement must be kept covered with film or sheeting, properly sealed, for 72 consecutive hours following the placing of the concrete except that, the film or sheeting may be temporarily removed so that joints may be sawed. While the pavement is uncovered, it shall be kept wet by sprinkling with water. (iii) Any joints or seams in a roll of burlap-polyethylene sheeting shall be double sewn. Concrete Pavement 603.03 - 411 - (iv) Joints and seams in polyethylene film or sheeting shall have a minimum lap of 18 inch es (450 mm), and sheeting shall be securely cemented together.
v.All joints and seams shall be sufficiently durable to prevent separation during the curing period.
3.Curing with wet burlap: (i) As soon as practical after the final finishing operations, burlap shall be carefully placed on the concrete and kept moist. Placement of burlap shall be done to avoid damaging the concrete surface. (ii) The burlap shall c onform to the requirements of Section 1011 and shall be of sufficient length to cover all exposed surfaces, including the vertical edges of the slab. (iii) At exposed vertical edges of the slabs, earth shall be banked so that the top width of the berm shall be at least 6 inches (150 mm). (iv) The burlap shall be kept continuously saturated with water for at least 72 hours following the placing of the concrete, except that the burlap may be temporarily removed so that the joints may be sawed. While the pavement is uncovered, it shall be kept wet by sprinkling with water. Concrete operations shall be suspended when water is not available to cure the concrete.
12.Joint Construction Procedures: a. (1) Joints shall be constructed to the dimensions shown in the contract or when “early-cut” type sawi ng of the joint, the cut shall be the depth recommended by the manufacturer. Curbed sections must be cut with a saw equipped with a diamond tipped blade.
2.Initial sawing shall begin when the concrete can support the weight of the saw and sawing does not create raveling. Sawing must be completed before random cracking occurs.
3.Joints over dowels shall not deviate from their intended location by more than 5% of the described spacing.
4.Doweled joints shall not deviate more than 1 inch (25 mm) from the center of the dowel's length.
5.Each transverse joint shall be cut to the described depth in one continuous pass.
6.Any panels that contain random cracking will be considered unacceptable. The Engineer will decide whether to replace or repair the panel. The Cont ractor shall replace or r epair these panels at the direction of the Engineer at no cost to the Department. A 20% deduction will be assessed on any repaired panel. Any panel that is replaced will not be assessed a 20% deduction.
7.Joints at gutters or integral curbs shall be cut to the proper depths to prevent random cracking.
b.Panels with spalls shall be repaired as directed by the Engineer.
c.The Contractor shall prepare and seal joints according to the manufacturer's recommendations.
603.03 Concrete Pavement
- 412 - (1) Before sealing, the joint wall (not the bottom of joint) surfaces shall be sandblasted or water-blasted to remove all dirt, curing compound residue, laitance, and any other foreign material. The Engineer may require additional measures, such as resawing, if the blasting techniques are ineffective. After sandblasting, the entire joint shall be cleaned with compressed air having a minimum pressure of 90 psi (620 kPa). The compressed air shall be free of oil, water, and other contaminants. The joints shall be dry at the time of sealing.
2.Transverse joints in Portland cement concrete pavements shall be sealed so that the joint is fill ed to approximately 1/4 inch to 5/8 inch (6 to 12 mm) below the top of the joint with an approved hot poured sealant.
i.All overflow material shall be removed from the surface of the pavement. (ii) If adhesion is not satisfactory, the material will be rejected, removed and replaced at no additional cost to the Department.
3.The Contractor shall give the Engineer one copy of the hot pour manufacturer's sealing recommendations two weeks prior to commencing work.
13.Surface Tests: a. The Contractor shall check all concrete pavement for smoothness as described in Section 602.
14.Integral Curbs a. The Contractor shall construc t integral curbs as shown in the contract. This curb shall be placed within 30 minutes after the slab has been placed and finished. That part of the pavement that will be attached to the integral curb shall be cleaned of all laitance and roughened to assure a good bond.
b.The Contractor may install the integral curb as a separate operation.
1.The Contractor shall instal l tie bars of the size and at the spacing shown in the contract.
2.The pavement upon which the curb is to be placed shall be finished with a rough texture.
c.The concrete for the integral curb shall be of the same class as that used in the concrete slab. All c ontraction or expansion joints in the pavement shall be continuous through the integral curb.
15.Opening Pavement to Traffic: a. No section of concrete pavem ent shall be opened to traffic until approval has been given by the Engineer.
b.The time for opening pavement will be based on the length of time the pavement is in place and/or on the compressive strength of the concrete as determined by cores taken from the pavement.
c.The Contractor’s forces may be allowed on the concrete pavement when the concrete has reached a minimum age of 14 days or when the concrete has reached a compressive strength of 3,000 psi (21 MPa) when tested in accordance with ASTM C 39. Concrete Pavement 603.05 - 413 - d. With the approval of the E ngineer, the Contractor may elect to increase the early strength of the concrete by adding cement and/or reducing the water/cement ratio. The pavement may then be opened to traffic provided it has attained a comp ressive strength of 3500 psi (24 MPa). The concrete in the area where the ea rly strength is required shall be paid for at the bid price.
e.When requested by the Co ntractor or the Department, the maturity method may be used to determine pavement compressive strength. The maturity method will be performed in accordance with NDOT C 1074 and in lieu of Subsection 603.03, Paragr aph 15.c. and d. to determine the strength of concrete pavement for the pur pose of early opening to traffic. Requests by the Contractor for use of the maturity method shall be on a project basis and shall be made in writing to the Engineer.
603.04 Method of Measurement
1.Concrete pavement is measured by the square yard (meter).
2.Concrete for pavement approaches is measured by the cubic yard (meter).
3.Reinforcing steel for concrete pavement approaches is measured by the pound (kilogram).
4."Portland Cement Concrete Pavement Smoothness Testing" is measured according to the procedure in Section 602.
5.Headers are measured by the cubic yard (meter) of concrete used. 6. If the concrete pavement includ es a beveled edge, the concrete pavement will be measured to the outs ide edge of the beveled edge. The work required to form the beveled edge will be considered subsidiary to the concrete pavement being placed.
603.05 Basis of Payment
1.Pay Item Pay Unit _____ inch (mm) Doweled Square Yard (SY) Concrete Pavement _____ [Square Meter (m 2)] _____ inch (mm) Concrete Square Yard (SY) Pavement _____ [Square Meter (m2)] _____ inch (mm) Reinforced Square Yard (SY) Concrete Pavement_____ [Square Meter (m2)] Concrete for Pavement Cubic Yard (CY) Approaches _____ [Cubic Meter (m3)] Epoxy Coated Reinforcing Steel Pound (lb.) for Pavement Approaches [kilogram (kg)] Portland Cement Concrete Lump Sum (LS) Smoothness Testing Concrete for Headers, Cubic Yard (CY) C l a s s _ _ _ _ _ [ C u b i c M e t e r ( m3)]
2.Payment will be based on the quantities shown in the contract unless changes are approved by the Engineer.
603.05 Concrete Pavement
- 414 - 3. Paving Units and Coring Program
a.Cores will be collected from paving units for the evaluation of compressive strength and thickness. Cores will be located randomly within each paving unit. Additional cores (speci al cores) for strength verification, thickness deficiency delineation or ot her anomalies may be taken at the discretion of the Engineer. These cores may be used in acceptance decisions.
b.(1) The paved area shall be divided into units. Each unit will be considered separately. Units are 750 linear feet (230 m) of pavement for each separately placed width, or width of each class of concrete whether or not placed separately starting at the beginning of the pavement.
2.The last unit for the width under consideration shall be 750 feet (230 m) plus any fractional part of 750 feet (230 m) remaining.
3.When the length of a separately placed width is less than 750 feet (230 m), the l ength of the unit shall be the actual length.
4.A separately placed width is the width between field constructed longitudinal joints, between a longitudinal construction joint and the edge, or between two pavement edges. A separately placed width may include more than one pay item of concrete, such as doweled and non- doweled.
5.Bridges and approach slabs shall be considered as exceptions to the unit’s length.
6.In cases of separately placed intersections or blockouts, the normal width of pavement on eit her side shall be considered as continuing through in the same manner as would be applicable if the section under consideration had been placed continuously through the section.
4.Compressive Strength Cores a. A pay factor will be applied to each unit based on the compressive strength of 1 core per unit tested in accordance with ASTM C
39.The Department will test concrete cores with a minimum age of 28 days. The Contractor will have the option to obt ain two additional cores, at no cost to the Department, for any un it core that fails to have the required minimum compressive strength provided:
1.The cores shall be obtained in accordance with ASTM C 42 and tested within seven (7) days of being notified of the strength deficiency, under the super vision of the Engineer.
2.The cores shall be cut within 6 inches of the original unit core in the longitudinal direction.
3.The results of all three cores sampled at the location will be averaged for the final compressive st rength calculation and pay factor.
b.When the primary designated core is deficient in thickness by more than 0.25 inch (6 mm), an additional core will be taken within 1 foot (300 mm) longitudinally of the primary core. The additional core can be used for compressive strength testing.
c.The pay factors are shown in Table 603.03. Concrete Pavement 603.05 - 415 - Table 603.03 Concrete Strength Pay Factor Percent of Required Concrete Compressive Strength Pay Factor Greater than 99.9 100 Greater than 98.5 to 99.9 99.75 Greater than 97.5 to 98.5 99.50 Greater than 96.0 to 97.5 99 Greater than 94.0 to 96.0 98 Greater than 92.0 to 94.0 97 Greater than 90.0 to 92.0 94 Greater than 88.0 to 90.0 90 Greater than 86.0 to 88.0 86 Greater than 84.0 to 86.0 81 Greater than 82.0 to 84.0 76 Greater than 80.0 to 82.0 70 Less than 80.0 See Paragraph 4.e of this Subsection
d.The pay factors for blockouts, intersections, and pavements not covered by coring shall be determined from the compressive strengths of their cylinders. If the concrete cylinders’ compressive strengths are less than 2,000 psi (14 MPa) at 7 days, then the Engineer may require the concrete to be removed and replaced.
e.The Engineer will evaluate the concrete’s expected use and may allow concrete with a compressive strength of less than 80% of the required strength (after 28 days) to be left in place and paid for at 40% of the bid price or may require the unit to be removed and replaced.
5.Thickness Cores a. Pavement shall be constructed to the minimum thickness shown in the contract. A pay factor shown in Table 603.04 will be applied to each unit based on the average thickness of cores tested in accordance with ASTM C 174.
b.At the option of the Engineer cores may not be required from irregular areas, blockouts, intersections, with widths less than 8 feet (2.4 m) or from an entire contract involving less than 5,000 square yards (4200 m 2) of pavement.
c.The thickness of a core shall be determined by averaging the measurement of three caliper readings taken at 3 equidistant points on the core.
1.If the unit core taken is not deficient by more than 0.25 inch (6 mm) from plan thickness, full payment will be made and no additional cores will be required.
2.If the unit core is deficie nt by more than 0.25 inch (6 mm), 2 additional cores will be taken in the same unit. Whenever possible, the distance between cores should be approxim ately one third of the unit length.
603.05 Concrete Pavement
- 416 - (3) The average thickness of the 3 cores will then be determined. If the average thickness of these 3 cores is not deficient by more than 0.25 inch (6 mm), full payment will be made.
4.If the average thickness of the cores is deficient by more than 0.25 inch (6 mm) but not more than 0.50 inch (12.5 mm) an adjusted unit price will be paid in accordance with Table 603.04. Cores deficient by more than 0.50 inch (12.5 mm) wi ll be treated as described in Subection 603.05 5.d.
5.When calculating the av erage thickness of the pavement unit, measurements greater than contra ct thickness will be considered contract thickness.
6.Exploratory cores for determining limits of deficiencies of more than 0.50 inch (12.5 mm) or special cores will not be used in determining average thickness.
7.The area deficient in thickness by more than 0.50 inch (12.5 mm) will be deducted from the to tal area of the unit and pay for the remainder of the unit will be based on Table 603.04. Table 603.04 Payment Deductions Based on Deficient Pavement Thickness English Average Thickness Deficiency (Metric) Percent o f Contract Unit Price 0 to 0.25 inch (0 to 6 mm) 100 Greater than 0.25 to 0.30 inch (6 to 7.6 mm) 85 Greater than 0.30 to 0.35 inch (7.6 to 8.9 mm) 80 Greater than 0.35 to 0.40 inch (8.9 to 10.2 mm) 75 Greater than 0.40 to 0.45 inch (10.2 to 11.4 mm) 70 Greater than 0.45 to 0.50 inch (11.4 to 12.5 mm) 65 Greater than 0.50 inch (12.5 mm) Remove and Replace* * When the thickness of the pavement is deficient by more than 0.50 inch (12.5 mm), the Engineer will evaluate the pavement’s expected use and may allow it to be left in place at 40% pay.
d.Remove and Replace Determination Procedure
1.When the measurement of any core is less than plan thickness by more than 0.50 inch (12.5 mm), the method to establish the limits of the 0.50 inch (12.5 mm) defic ient section will be determined by taking exploratory cores in the following manner.
2.Cores will be taken 5 feet (1.5 m) either side of the deficient core’s locations on a line para llel to the centerline of the pavement.
3.If both cores are within the 0.50 inch (12.5 mm) tolerance, no additional cores will be taken for this individual zone of deficiency.
4.If either or both of these cores are not within the 0.50 inch (12.5 mm) tolerance, additional cores wi ll be cut on either si de of the original Concrete Pavement 603.05 - 417 - deficient core on a line parallel to t he centerline of the pavement. These additional cores shall be taken 25.0 feet (7.6 m) from the original core and then consecutive cores will be cut at 40 foot (15 m) intervals until a thickness within the 0.50 inch (12.5 mm) tole rance is found in both directions.
5.On either side of the original short core, the procedure will be to take a core approximately halfway between the first core that comes within the 0.50 inch (12.5 mm) toleranc e and the nearest core over 0.50 inch (12.5 mm) deficient.
6.This procedure will be repeated until the location (plus or minus 5 feet) (1.5 m) at which the pavement comes within the 0.50 inch (12.5 mm) tolerance is located.
7.Once the limits are located, payment will be made as defined in Table 603.04 for deficiencie s greater than 0.50 inch (12.5 mm).
6.Cement Content Deduction: a. The cement content deduc tion is applicable to concrete pavement under the following conditions:
1.Batching equipment is determined to be faulty during concrete paving operations.
2.Concrete pavement is constructed under a QC/QA specification.
b.Cement content, as a percen tage by weight of the specified concrete (regardless of its intended us e) shall be determined as described by ASTM C 138.
c.(1) If the average of 10 cons ecutive cement content tests is less than 100% of the specified wei ght, then a deduction shall be made as described in Table 603.05.
2.The amount of placed concre te that is to have its payment adjusted by the cement content deduction pay factor shall include all concrete represented by the 10 consecutive tests.
d.(1) If the average ce ment content percentage for 10 consecutive tests is 100% or more of the specified weight and any individual test is less than 97%, then a deduction is made as described in Table 603.06.
2.The amount of placed concre te that is to have its payment adjusted by the cement content deduction pay factor shall include all concrete that is placed between the test just prior to the low percentage test and the first test following the low percent age test that is at or above 97%.
603.05 Concrete Pavement
- 418 - Table 603.05 PCC Concrete Deduction for Cement Content (Average of Ten Consecutive Tests) Average Cement Content – By Weight PCC Concrete Pay Factor 100 or greater 1.00 Less than 100 to 99.7 0.98 Less than 99.7 to 99.5 0.95 Less than 99.5 to 99.2 0.85 Less than 99.2 to 99.0 0.85 Less than 99.0 to 98.5 0.70 Less than 98.5 to 98.0 0.625 Less than 98.0 to 97.5 0.550 Less than 97.5 to 97.0 0.475 Less than 97.0 Remove and Replace* * The Engineer may elect to leave concrete in place and pay only 40% of bid price. Table 603.06 PCC Concrete Deduction for Cement Content (Individual Test) Cement Content Percentage (by weight) PCC Concrete Pay Factor 100 to 97 1.00 Less than 97.0 to 96.5 0.98 Less than 96.5 to 96.0 0.95 Less than 96.0 to 95.0 0.88 Less than 95.0 to 94.0 0.76 Less than 94.0 to 93.0 0.64 Less than 93.0 to 92.0 0.52 Less than 92 Remove and Replace* * The Engineer may elect to leave concrete in place and pay only 40% of bid price.
7.No additional payment over the contract unit bid price will be made for any pavement, which has an average thickness greater than shown in the contract.
8.The preparation of the subg rade under the pavement approaches shall not be measured and paid for directly but shall be considered subsidiary to the concrete pavement.
9.Direct payment will not be made for integral curbs. They shall be considered as subsidiary to concrete pavement. Concrete Pavement 603.05 - 419 - 10. Furnishing and placing required reinforcement and dowel bars shall not be paid for directly but will be considered as subsidiary to concrete pavement.
11.Water incidental to the concrete placement shall be considered subsidiary to c oncrete pavement.
12.If varying types and thicknesses of concrete are required, the pay item will be subdivided so that the quantities of the various types and thicknesses will be identified.
13.Securing and tying reinforcing bars will not be paid for directly but shall be considered subsidiary to the items of work for which direct payment is made.
14.Payment is full compensation for all work described in this Section. - 420 - SECTION 604 -- CONCRETE BASE COURSE
604.01 Description
1.This work shall consist of furnishing all materials and constructing a base course composed of Portland cement concrete. It shall be constructed on a prepared subgrade or foundation c ourse as shown in the contract.
604.02 Material Requirements
1.The base course concrete shall be Class 47B-3,000 (47B-20)
2.All materials shall be furnished by the Contractor and shall conform to the requirements in Table 604.01. Table 604.01 Material Requirements Applicable Materials Section Portland Cement Concrete ........................ 1002 Joint Sealing Filler ..................................... 1014 Preformed Joint Filler ................................. 1015 Reinforcing St eel ....................................... 1020, 1021, 1024 Deformed Metal Join t Material ................... 1027 Curing Materi als......................................... 101 0, 1011, 1012, 1013 Dowel Bars ................................................ 1022 Aggregates ................................................ 1033 Admixtures ................................................. 1007 Water ......................................................... 1005
604.03 Equipment
1.The equipment used and the calibration responsibility shall be as described in Sections 601 and 603.
604.04 Construction Methods
1.The Contractor shall prepar e the subgrade and foundation course as described in Sections 30 1, 302, 303, 305, and 307.
2.Concrete base course shall be constructed in accordance with the pertinent sections of Section 603.
3.The surface of the concrete base course shall be tested for smoothness in both the transverse and long itudinal directions with a 10 foot (3 m) straightedge. The maximum allowable variation is 1/4 inch (6 mm). Base course not meeting this requirement will be evaluated by the Engineer and may be subject to corrective diamond grinding or other remedy.
4.a. When a bituminous or asph altic concrete surface is to be placed on the base course, a bituminous liquid curing compound conforming to the requirements of Se ction 1013 shall be applied.
b.The rate of application shal l be determined from the results of moisture retention tests, except that the rate of application shall never be less than 1 Gal/200 SF (2 L/m2) of surface area.
c.In the event that the cure coating is damaged within 72 hours after being applied, the affected areas sh all be recoated without delay at the same rate described for the original application.
5.a. The base course may be opened for hauling and placing the wearing or surface course after the concrete has cured 14 days or after
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 437–453 of 1,048.