700-3 CONCRETE HAULING EQUIPMENT
When central mixed concrete is used, the Plant Technician should check each truck for compliance with the Specifications. All batch trucks should be inspected by the Plant Technician before being permitted to be used on the project. The batch dividers should fit tightly, and the compartments should be large enough to prevent any spillage during discharge.
The Plant Technician and the Roadway Technician must both keep check on time and length of haul. The time of haul, whether in agitating or non-agitating truck bodies, should not exceed the limits indicated in
Article 700-3 of the Specifications. The elapsed time is defined as the period from first contact between mixing water and cement until the entire operation of placing and
finishing up to micro-surfacing (burlap drag, or Astroturf drag), including corrective measures if necessary, has been completed. Under no circumstances, should the haul be long enough to cause loss of workability before finishing.
If the anticipated haul time exceeds the elapsed time defined in this Article, an extension may be allowed by the Engineer provided the concrete maintains mixture uniformity. Test procedure ASTM C94 Annex is used for determining mixture uniformity. The Materials and Tests Unit can be called to offer assistance when checking for mixture uniformity. Provided the concrete passes any
five (5) of the
six (6) concrete tests listed in the Annex, the elapsed time may be extended up to
1.5 hours.
700-4 PREPARATION OF SUBGRADE AND BASE
Divisions 5 and
6 of this Manual and of the Standard Specifications provide adequate guidance for the preparation of the subgrade and base. The Specifications require that the subgrade and base for concrete pavement be prepared using an automatically controlled, fine-grading and paving equipment to produce the final subgrade elevations and asphalt base surfaces. This requirement may be waived by the Engineer in locations or areas where its use is not practical, with the concurrence of the State Construction Engineer.
The base course should provide a uniform support for the concrete pavement. Typically, an asphalt surface mix is placed on the subgrade to protect the subgrade from exposure to moisture from above. An asphalt drainage course (PADL
or Asphalt Base Course) or geotextile capable of conveying water is placed on top of the surface mix to act as a drainage layer. It is important to obtain as much density as possible in the asphalt surface mix to close as many air voids as possible; however, the drainage course should be left with interconnected air voids to assist with conveying water while providing a stable platform for paving. The density requirements for the asphalt drainage layer may be relaxed for this type of use. Construction Traffic should be limited on the asphalt layers beneath the proposed concrete pavement.
Prepare the subgrade and base beneath Portland cement concrete pavement in accordance with the applicable sections of these Specifications and with a grading tolerance of ± 1/4" from the established grade on mainline lanes and a grading tolerance of ± 1/2" in all other areas. Use approved automatically controlled grading and paving equipment to produce final subgrade and base surfaces meeting the lines, grades and cross sections required by the plans or as directed. When in the judgment of the Engineer the use of such equipment is impractical, this requirement will be waived.
Ideally the same stringline and/or machine guidance system would be used for fine grading operations, placing the asphalt base courses, and pouring the concrete pavement. Care should be taken to ensure the string line does not have any sags and is tight. The spacing of the pins used to support the stringline should be spaced no farther than
50 feet apart in tangent sections. This spacing should be reduced to no farther than
25 feet in vertical or horizontal curves.
700-5 PLACING CONCRETE
Because proper construction practices are critical to the concrete pavement’s service life, the Roadway Technician and the Laboratory Technician should ensure that placement of concrete shall not begin or shall be suspended when the following conditions occur:
- When the descending air temperature in the shade away from artificial heat reaches 35°F, paving may resume only when the chance of freezing is nonexistent and weather forecast is projected to reach a high of 40°F for that day's operation and the ambient temperature is above 32°F.
- When the subgrade or base course is frozen.
- When the aggregates to be used in the mix contain frozen particles.
- When air temperature in shade is 90°F and rising or the concrete temperature is greater than 95°F.
When additional pavement, aggregate or soil must be placed adjacent to new pavement by machine methods, do not place it until the concrete has attained a compressive strength of at least
3000 psi. This means that the paver or any other equipment weighing over
1000 lbs. should not ride on the pavement until the estimated compressive strength reaches
3000 psi.
A Roadway Technician must be present at all times when concrete is being placed. The Technician shall check and approve all aspects of the concrete paving operation - equipment, forms, string lines, etc. - prior to permitting the concrete paving operation to proceed. Particular attention should be placed upon the proper operation of the paver control systems and the possibility of stringline sag. The Contractor shall not be permitted to use control components that do not properly operate or conform to the manufacturer's suggested methods of operation. Assistance in checking the Contractor's equipment may be obtained by contacting the
Pavement Construction Section of the Construction Unit.
It should be noted that the use of fixed continuous reference lines is required for both horizontal and vertical control. The Specifications allow modification of this requirement. The State Construction Engineer should be consulted prior to granting the Contractor’s request to utilize mobile reference lines for vertical control.
The base material, except in the case of
Cement Treated Base Course, should be thoroughly dampened ahead of the placement of the concrete by the Contractor. The moistened base shall be maintained in this condition until such time as the concrete is placed thereon. When paving in the heat of the summer, white pigmented curing compound may be applied to the asphalt base to reflect some of the sun’s radiant heat.
All dowel bar assemblies, dowel bars, and tie bars required by the plans should be thoroughly checked for conformity well ahead of the concrete placing operations. If the Contractor wishes to use a DBI (Dowel Bar Inserter) written approval will be necessary from the
Pavement Construction Engineer.
Slump tests shall be performed in accordance with the procedure and at the rates given in the
Portland Cement Concrete Certification Study Guide.
The testing for entrained air shall be performed on each compressive strength lot using a pressure type air meter. The results of such tests should be sent back to the batching plant in order that the Plant (Batch) Technician may know whether the amount of air entraining agent being added to the mix is correct. Quick checks for information only may be made with the AE55; however, such testing is not intended to replace the test required to be run by the pressure method.
The provisions of this article relative to temperature limitations shall be rigidly enforced. In addition, paving shall be delayed or discontinued at any time when deflection of forms due to wet subgrade or base material indicates that the pavement will be deficient in thickness, or provide an unsatisfactory riding surface.
The concrete must be uniformly spread across the typical section. Concrete with uniform consistency will be easily workable without segregation. If excessive segregation or difficult concrete workability is observed, or if there is evidence of free water on the surface before or after spreading the concrete, an immediate investigation and determination of the cause of such conditions should be made.
The concrete must be uniformly spread across the typical section. The spreading of the concrete should be performed with a mechanical spreader independent of the paver. The spreader should provide a consistent supply of concrete in front of the paver to allow the paver to maintain a constant speed. Some pavers are described as a paver/spreader but the spreader should be independent of the paver. All other things being equal, a heavier paver generally produces a smoother pavement because it is less affected by surges of concrete coming into the paver.
The paver should be operated in a continuous forward movement and all operations of mixing, delivering and spreading should be coordinated to provide uniform progress and minimize stopping and starting of the paver.
700-6 VIBRATING CONCRETE
Concrete vibrators, whether the pan or internal type, should be checked for vibration frequency before use. The pan type of vibrator is designed to apply vibration to the surface of the concrete uniformly for the full width of the pavement. The internal type must be equipped with vibratory units, so spaced that the effective area of vibration of each unit will slightly overlap that of the next unit. There must be sufficient units to vibrate the entire width of pavement.
The internal vibrating elements should be set to vibrate at
1/2 the slab depth. Pan or internal type vibrators should be raised from the concrete or cutoff when the unit is not moving forward to avoid over vibration.
The Contractor should furnish and operate an electronic vibratory monitoring device, displaying information such as operating frequency of each individual vibrator. A report which details the number of impulses from each vibrator should be reviewed by the Technician to verify that all vibrators are operating within the specified allowances.
The Technician should immediately inform the contractor if he notices any vibrator not operating within the allowable frequencies and inspect the slab behind the paver for any streaks of segregation.
700-7 FINISHING
Refer to
Articles 710-6 and
720-7 for details on finishing concrete pavement or concrete shoulders, respectively. Do not use excessive water for finishing.
700-8 PROTECTION OF PORTLAND CEMENT CONCRETE PAVEMENT
(A) GENERAL
The Specifications place the burden of protection of the concrete from environmental conditions upon the Contractor. However, it is often very difficult to make a determination of precisely how much damage has occurred and whether or not repairs can be made, or if the damaged pavement must be removed and replaced. The Area Construction Engineer
is available to assist the Engineer in determining the extent of any damage and the appropriate remedial action that may be required.
Materials to protect the concrete pavement during the curing period should be readily available at the paving train.
(B) COLD WEATHER
In cold weather it is important to protect the concrete from freezing and to maintain curing conditions to ensure adequate strength development. If concrete freezes during the initial curing period, it may not continue to gain strength in a manner consistent with normal concrete performance. Some instances have shown that the maximum strength was
1/2 of what was anticipated.
When fresh pavement is exposed to possible freezing conditions, the Technician should record the high and low temperature for each
24-hour period on the surface of the slab beneath the protective covering
each day. The surface and internal temperature of the pavement slab should be monitored further by using maturity meters. Because the corners are most heavily exposed to the environmental conditions, this is a good location to monitor the temperature of the slab.
The concrete slab must be protected from freezing during the entire initial curing period of the concrete pavement. The recording of temperatures should also be continued throughout this duration. The air temperature in the shade and away from artificial heat should be recorded during the same period and at the same frequency. This information should be included in the
project diary.
(C) HOT WEATHER
Hot weather conditions, high concrete temperature, wind and low relative humidity, or combinations thereof can cause rapid evaporation of the concrete pavement, which significantly increases the likelihood, that plastic shrinkage cracking or drying shrinkage cracking will occur.
The high rate of evaporation can dry and remove surface water beneficial for proper hydration unless proper moist curing methods are employed. High temperatures accelerate slump loss, and can cause some loss of entrained-air, and increase water demand resulting in lower compressive strength. Temperature also greatly affects the setting time of concrete.
When paving in hot weather all facets of the paving operations should be watched closely. Concrete should be placed in a timely manner. Curing should be applied as soon as possible to hold in the water needed for hydration of the concrete and to prevent plastic shrinkage cracking.
(D) RAIN
A check of the availability of protective covering at the job site for protection from rain should be made and recorded in the project diary. The use of polyethylene film for this purpose is practically universal but serious surface slicking can result from its use. Efforts by the Contractor to protect the pavement during a rainstorm and restore the surface finish after a rainstorm should be encouraged, if appropriate, and fully recorded in the
project diary. The Contractor will be responsible for providing a pavement and pavement surface that meets the Specifications.
700-9 CURING
(A) GENERAL
Curing is one of the most important phases of concrete paving. Proper curing will minimize shrinkage cracking and future surface wear.
The curing process must be started as soon as possible after the surface water film has disappeared but while the surface is still in a moist condition. All curing material must be uniformly applied to the top and sides of the slab at the specified rate or thickness.
A curing day is any consecutive
24-hour period beginning with the mixing of the concrete when the air temperature next to the slab does not fall below
4°C (40°F). During cool periods, a hi low thermometer should be used to keep a daily check on the temperature beneath the protective covering. These readings shall be recorded in the project diary. Refer to
Section 1026 of the Standard Specifications for more details on curing agents for concrete.
(B) MEMBRANE CURING COMPOUND
Membrane curing compound is accepted by lot number after it has been tested and approved for use by the
Materials & Tests Unit. It may be used from the date of manufacture until its expiration date,
one year later. The expiration date shall be listed on the container. Membrane curing compound will not be retested and may not be used after the expiration date.
Membrane curing compound should be agitated in the container before and during application. It should not be used until thoroughly mixed. This can be accomplished by use of compressed air or mechanical agitators. The machine used to apply the curing compound should be equipped with an agitator, pump and inline flow metering device. The Technician should check to see that spray nozzles are clean and deliver a uniform coverage over the full width of the slab. For pavement constructed using forms, curing shall be applied to the sides of the slab immediately after the removal of the form. The rate of application should be checked for compliance with Specifications. Only white pigmented membrane compound may be used for curing concrete pavement. The membrane curing compound film shall be protected from damage at all times and if damaged, repaired as soon as possible.
The newly placed concrete should not be exposed for long periods before curing compound is applied. As a general guideline, it should be covered within
30 minutes; however, this time frame may vary with the temperature and/or the season. In warmer temperatures this time period may need to be reduced, and in colder temperatures this time period may be extended. Regardless of the season, the pavement surface should covered as soon as possible after the sheen has disappeared from the slab.
(C) POLYETHYLENE FILM
The Specifications are specific in the requirements for the use of several other methods for curing concrete pavement. If other methods are used, the Roadway Technician should see that the Contractor strictly adheres to all requirements.
(D) BURLAP
While the use of burlap material is not very common due to its cost and labor intensity, Contractors may elect to use fully saturated burlap sheets to cure the smaller pours. The burlap material must remain saturated throughout the curing period.
700-10 REMOVING FORMS
The concrete shall be at least
12 hours old before removing forms. All honeycombed areas must be repaired immediately after the forms are removed. Curing compound should be applied to the newly exposed surfaces.
700-11 JOINT CONSTRUCTION
(A) GENERAL
After placing and finishing concrete pavement, saw cuts are created to control the location of cracking and to provide relief for concrete expansion caused by temperature and moisture changes. Contraction joints, both transverse and longitudinal, are designed to give a deliberate plane of weakness in the slab such that cracks caused by shrinking of the concrete during hardening and temperature variations will form in a neat line, thus eliminating irregular, unsightly, spall-susceptible cracking. The joint must also be formed such that it can be sealed with a flexible adhesive material to waterproof the subsequent cracks.
Transverse joints are cut in the concrete slabs directly over dowel bars such that once the concrete does crack the dowel bar will assist with the transfer of live loads from one concrete panel to the next without displacement or faulting of the joint. Longitudinal joints are cut directly over tie bars such that the two lanes will still be physically attached even in the presence of a full depth controlled crack.
Both transverse and longitudinal joints should be formed using an early entry dry cutting and/or approved saw system. Any change from the procedure set forth in the plans, standard drawings, and Specifications must be approved by the State Construction Engineer.
Joint construction is an area where proper techniques and thorough inspection by project personnel can contribute immensely in reducing future maintenance costs. The cost of maintenance of joints in concrete pavement can be almost directly related to the workmanship which went into the original construction of the joints. This maintenance involves repairing of spalled concrete, faulted joints, and non-adhesion of joint sealer. Not only does poor joint construction increase maintenance costs, but it also results in poor rideability and subsequent public criticism. Accordingly, the Technician should be thoroughly familiar with the Specifications, plans and standard drawing requirements, and the guidelines set forth in this Manual. Refer to the most recent version of the
Roadway Standard Drawings or contract special provisions for specific details on joint construction, details, dimensions, layout (spacing), dowel assembly details, header details, etc. See
Drawing Nos. 700.01 through 710.01.
All joints shall be constructed in accordance with the joint detail required by the plans and/or standard drawings. The joints shall be sawed or formed with the joints spaced as required by the plan details. The initial saw cut to provide stress relief shall be at such interval and frequency to control random cracking.
Defining the initial sawing window in the field can be done by the
scratch test method. Experienced saw operators and technicians rely on judgement and the scratch test to estimate the appropriate time to saw the joints. The test involves scratching the concrete surface with a nail or knife blade, and then examining the depth, uniformity, and influence on the surface. In general, if the scratch removes the surface texture, it is too early to saw without raveling problems.
The time for sawing joints will vary, depending upon weather, atmospheric conditions, and the aggregate. When the weather is hot or windy, it is to be expected that the available sawing window will be narrowed and therefore, sawing will need to be performed earlier. However, on colder more humid paving days, the window for sawing may be expanded. In most cases, joints need to be sawed within
seven hours after placement of concrete with an
early entry dry-cutting sawing system. Frequent checks should be made by measurement of joint widths and depths.
When the Contractor is cutting transverse and longitudinal joints, a Roadway Technician should be present to document the time after placement of the slab when the sawing operation began and was completed as well as the depths of the initial and final saw cuts. These depths and times should be recorded in a pay record book and noted in the
Technician’s Daily Report.
To minimize joint spalling, it is essential that no non-compressible materials such as grout, sand, gravel, pieces of concrete, dirt, etc., be allowed within the initial or final cuts of the Transverse and Longitudinal joints during construction operations. When the Contractor is cutting the initial cuts, Transverse or Longitudinal, the residue from the sawing operation should be cleaned out and away from the
1/8” initial cut and kept clean during the construction phase of the project until the “reservoir cut” is made, cleaned, and sealed.
In addition, when placing concrete adjacent to a previously poured pavement, the void from the saw cut and any crack opening should be taped or protected to prevent grout from the newly poured slab from intruding into the opening. Care must be given for the top surface of the slab as the grout is often displaced during finishing operations and this grout can fall into the sawn opening.
(B) TRANSVERSE CONTRACTION JOINTS
The project personnel should check the dowel basket assemblies at the site. The baskets should be visually checked by the Roadway Technician for compliance with the contract requirements and to verify that the dowel assembly has not been damaged, misaligned, or otherwise installed in an unsatisfactory manner. The dowel assemblies are normally inspected at the fabricator's site by the Materials & Tests Unit or their agent and tagged accordingly. If the dowel assemblies do not appear to be within compliance with the contract requirements, call the
M&T Section Specialist for your area.
The locations of the dowels must be accurately referenced transversely such that the sawed joint can be placed exactly over the centerline of the dowel assemblies. "Locked joints" can develop if the dowels are not placed parallel to the profile grade line, if the assemblies are not adequately fastened down, if burrs are not removed from the dowels, or if the dowels are not properly coated. It is important to ensure that the dowel baskets are secured properly to the surface. The baskets may be displaced or shifted by the concrete surge caused by the spreading and/or finishing machine.
When staking pins are used to secure the basket assembly, the pins should be on the opposite side of the approaching paver. Staking the basket down this way will reduce the likelihood of the basket becoming dislodged when the spreader and paver pass through.
After the dowel baskets are set and secured, the spreader wires used to hold the dowel assembly together should be cut to allow unrestricted movement at the joint and allow further testing for appropriate location.
Frequent visual observation should be made by the Roadway Technician during the spreading of the Portland Cement Concrete to verify the head of material in front of the spreader and/or paver is not displacing the dowel baskets and tie bars. The location of the joints with respect to dowels and tie bars should be checked frequently by probing or by using a metal detector to insure that they are in correct position.
A MIT Scan is able to verify the alignment of the dowels should there be any question about the basket assembly or dowel alignment. Contact the
Materials and Tests Unit for assistance with the MIT Scan.
(C) LONGITUDINAL CONTRACTION JOINTS
A longitudinal joint is necessary whenever the width of pavement poured is greater than
16 feet. Care should be taken not to place a longitudinal joint in the final wheel path. All longitudinal contraction joints shall be sawed directly over tie bars. The sawed joint must be sawed within
seven hours of concrete placement with an
early entry dry-cutting and and/or approved sawing system.
All tie bars for longitudinal contraction joints are deformed and must be placed at right angle to the joint. The horizontal and vertical placement of these bars should be periodically checked for conformity with the plans.
Where longitudinal contraction joints are required, the joints should be placed at the location of the permanent proposed traffic lanes.
(D) TRANSVERSE CONSTRUCTION JOINTS
"Planned Transverse Construction Joints" are those joints necessitated by the suspension of work at the end of a workday. These joints are to be made at the same location as required for a transverse contraction joint.
There are
two common construction methods for planned transverse construction joints. Some contractors elect to use a header board. If a header board is used, it must be perpendicular to the profile grade line and must support dowel bars parallel to the profile grade line. Adequate hand vibration is required in the areas adjacent to the header board. Other Contractors elect to saw the slab full depth and drill and epoxy dowel bars into the sawn face of the slab. This method of planned construction joint often yields smoother transverse joints.
"Emergency Transverse Construction Joints" are those transverse joints required when concrete placement has been suspended for more than
30 minutes for any reason. This joint shall not be formed or sawed but shall be a butt joint. An emergency transverse joint shall not be within
six feet of a planned transverse contraction joint and shall not affect the spacing of transverse contraction joints.
Emergency Transverse joints require the placement of deformed tie bars that are equal to the diameter of dowel bars. The reason for the deformed tie bars is to purposely create a locked joint.
If the Contractor elects to use a header board to construct an emergency joint, the board must be perpendicular to the profile grade line and shall support deformed tie bars parallel to the profile grade line. Adequate hand vibration is required.
The operation of starting or stopping concrete pavement construction is always a critical one and the quality of work performed at the headers will often determine the final ride quality of the pavement. The Roadway Technician should always be present and observing that the proper amount of vibration and finishing work is performed and that dowels or tie bars, where required, are properly aligned and spaced. Care should be exercised to prevent “dead concrete” or mortar, which has built-up on equipment during the day's operation, from being placed in the fresh concrete near the header. The Technician should use good judgment in this matter but may direct the removal of concrete so contaminated when the contamination will apparently be detrimental to the finished pavement. This inspection task is very important in helping to prevent future maintenance problems and costs.
(E) LONGITUDINAL CONSTRUCTION JOINTS
Longitudinal Construction Joints constructed in accordance with the referenced standards are permitted for pavement widths in excess of
16 feet, such as for additional traffic lanes and acceleration/deceleration ramp tie ins.
Normally, tie bars are required for longitudinal joints for both slip form and fixed form paving and are placed into the plastic concrete by hand. With the slip form method, it is suggested that a form board predrilled with the correct size holes and spacing be placed flush with the sides of the pavement and the bars then pushed into the concrete. This eliminates edge slump and surface distortion problems. Edge slump should be monitored constantly to ensure that the
1/4-inch maximum is not exceeded.
In either event, where longitudinal construction joints are required, the joints should be placed at the location of the permanent proposed traffic lanes.
(F) TRANSVERSE EXPANSION JOINTS
Transverse Expansion Joints in concrete pavement are normally placed at or near bridge approaches. The baskets for expansion joints should be checked prior to beginning the areas around the expansion joints for compliance. The Bridge Technician should make a sketch of which dowel bars have expansion caps on them at the approach slab so that the PCCP Roadway Technician can place his expansion caps on the correct dowels (
See 700.03 Sheet 2 or 2 of the Standard Drawing “Partial Plan Expansion” Section). If no drawing exists, the expansion caps would be placed on each of the dowels.
Expansion joints are placed to help prevent cracking due to thermal expansion in concrete. They provide a complete separation between two parts of a slab. The separation is sealed with silicone sealant to allow movement of the slabs and to prevent buckling. Accordingly, it is absolutely necessary that no non-compressible materials such as stone, gravel, pieces of concrete, dirt, etc., be allowed within the expansion joints during construction. The design also provides for load transfer from one slab to another by means of dowel bars. The same care must be exercised here as discussed in Item (B) above.
VERIFICATION OF DOWEL BAR ALIGNMENT
In
Subarticle 700-11(G) “Verification of Dowel Bar Alignment” the specifications require the use either properly secured dowel baskets or a dowel bar inserter, provided the ability to correctly locate and align the dowels at the joints is demonstrated. Contact the Materials and Tests Unit when beginning placement of dowels and tie bars.
The contractor is to provide a calibrated magnetic imaging device that will document the dowel bar location and alignment. The contractor will utilize this device as a part of his process control and make any necessary adjustments to ensure the dowels are placed in the correct location.
The contractor will scan at least
25% of the joints in the initial placement or
1.0 mile of pavement, whichever is greater, at random intervals throughout the pavement each time the paving train is mobilized.
He will scan all joints in this initial section if the dowel bars exhibit side shift, horizontal displacement, vertical displacement, horizontal misalignment, or vertical misalignment, above the allowable tolerances defined below. In addition, he will continue scanning
25% of the joints until it is established that the dowel bar inserter or secured dowel basket assemblies are consistently being placed at the correct location (meeting the tolerances defined below). Once the engineer determines that consistency is established, the contractor may reduce the percentage of scanned joints to
10%. At any time, inconsistency in the placement of the dowel bars become evident, additional scanning may be required up to
100% of the joints.
If the consistency of the proper dowel bar alignment cannot be established within a reasonable time frame, the Engineer will have the option of suspending the paving operation.
The contractor will provide a report of the scanned joints. This report should include the station and lane of the joint scanned, as well as the horizontal location, depth, horizontal and vertical misalignment, and lateral displacement or side shift of each dowel bar in the joint. The joint score described below should also be provided in the report.
Side shift is defined as the position of the center of the dowel bar in relation to the sawed joint. The maximum allowable side shift is
2 inches.
Horizontal displacement is defined as difference in the actual dowel bar location from its theoretical position as detailed in the standard details. The maximum allowable horizontal displacement is
2 inches.
Vertical displacement (depth) is the difference in the actual dowel bar location from the theoretical midpoint of the slab. The maximum allowable vertical displacement depth is
1/2 inch.
Dowel bar misalignment is defined as the difference in position of the dowel bar ends with respect to each other. Vertical misalignment is measured in the vertical axis whereas horizontal misalignment is measured in the horizontal axis.
Example: A joint has 12 bars. 10 are aligned correctly. 1 bar is misaligned 16mm, and 1 bar is misaligned 22mm.
The joint score is a measure of combined effects of horizontal and vertical misalignment. The joint score is determined by summing the product of the weight (shown in the table below) and the number of bars in each misalignment category and adding
1. The vertical and horizontal dowel misalignment should be evaluated, and the greater misalignment shall be utilized in determining the joint score.
Identify any scanned joints where the opposing horizontal or vertical misalignment of any
two bars within the joint exceeds
1 inch. This situation will be considered a locked joint.
When a locked joint as defined above is discovered, scan the two joints immediately adjacent to the locked joint. If either of the adjacent joints are deemed to be locked, provide a written proposal to address the dowel misalignment for each locked joint. No corrective action should be performed without written approval.
Any and all corrective action necessitated by improper joint alignment shall be at no cost to the Department.
Construction traffic may operate over joints, which have been initially sawed only. No traffic of any type will be allowed on the pavement after the final sawing joints until the installation of the joint sealer has been completed and the sealer is tack free. The sawing and sealing of all joints must be complete before permanent traffic is placed on the pavement.
The minimum air temperature is very critical to good joint and sealant performance. Placing sealant when the temperature is less than
7oC (45oF) should not be allowed unless approved by the State Roadway Construction Engineer.
The joint shall not be filled until it has been resawed, cleaned, and dried. This shall be accomplished by sandblasting. Just prior to sealing, the joint is "blown out" with compressed air. It is extremely important that the compressor used to supply air for cleaning joints be equipped with traps, which will remove compressor oil and water from the air supply. Oil or water stains on the joint wall will prevent the proper bonding of low modulus silicone sealant to the joint wall. The Technician shall specifically check to ensure the compressor is equipped with the traps noted above.
Cleaning is best achieved by good workmanship during placement of the sealant. Refer to the sealant manufacturer’s recommendations for curing requirements.
The timely opening of Portland Cement Concrete pavement or PCCP to traffic is often extremely important. However if traffic, especially construction traffic, is allowed on the pavement before the concrete has gained sufficient strength, the service life of the concrete pavement may be adversely compromised. Therefore, no traffic, including construction traffic, is allowed on the completed pavement slabs until the compressive strength of the concrete has reached
3000 psi.
To determine the compressive strength of the concrete, the maturity method will be used. To determine the compressive strength of the concrete using the maturity method, a strength-maturity relationship must be developed and verified. The procedures for developing the maturity curve, estimating the in-place concrete’s strength, and verifying the maturity curve are included in the
Construction and Inspection of Portland Cement Concrete Pavement Manual.
In the absence of a strength maturity curve, traffic should not be allowed on the concrete slab until test beams representative of the pavement have attained a compressive strength of
3000 psi.
For the placement of permanent traffic, the sawing and sealing of all joints must have been completed. Construction traffic may operate over joints which have been initially sawed only. No traffic of any type will be allowed on the pavement after the final sawing joints until the installation of the joint sealer has been completed and the sealer is tack free.
The Specifications require the Contractor to perform process control sampling and testing of concrete materials, the finished concrete mix, and the paving operations to ensure the pavement meets the requirements of the Specifications.
The sample taken for determination of the air content should be obtained as soon as the concrete is discharged on the road. All concrete that does not meet the Specifications must be fully removed from the road and not incorporated into the final pavement structure.
The Engineer and the project personnel should carefully review the method and procedure for establishing lots. This procedure is very important because it will determine the square yardage of concrete to be affected if an adjustment in pay is necessary. There are several different items to be concerned with, such as the width of the paving operation and the type of pavement; i.e., mainline, ramp, miscellaneous, etc. The Specifications list the criteria for each case and outline the procedures which are to be followed. The Area Construction Engineer should be consulted if there are any questions on the methods and procedures for establishing lots.
The Specifications give the procedures that are to be followed in determining the “pay factors” as they apply to compressive strength. In order to standardize the procedures, the following will apply:
Whenever the compressive strength cylinders indicate concrete that fails to meet the minimum compressive strength specified, the Engineer shall immediately notify the State Roadway Construction Engineer.
The thickness of both concrete pavement and concrete shoulders are determined for acceptance purposes by obtaining cores from the pavement or shoulder. It is important that the same lot determination used for compressive strength be used to determine the acceptable thickness of the pavement.
The Contractor and/or the Engineer should contact the Materials and Tests Unit prior to beginning work to determine when field certification training and the required examination(s) can be scheduled for Technicians and equipment involved with the PCCP International Roughness Index.
