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Airfield Joints

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Figure 1. properly jointed concrete airfield pavement.

Properly designed airfield pavement joints (Figure 1):

  1. Control cracking due to aircraft loads and restrained curling and warping stresses.
  2. Afford adequate load transfer across thejoints.
  3. Limit infiltration of foreign material into the joints.

Joints also divide the pavement into suitable increments for construction and accommodate pavement movements at intersections with other pavements or structures. Joint design is an integral part of pavement design for concrete airfield features. To satisfy the basic pavement design assumptions, joints must provide adequate transfer of loads from one panel to the next. Load transfer is obtained by using mechanical load transfer (dowels) or by aggre­gate interlock. A cement ­treated subbase (CTB)also will provide substantial joint support. Increasing the thickness of a pavement along certain joints is an alternative means of reducing slab bending stresses and edge deflections, allowing for adequate joint performance.


Overview of Joint Types

Figure 2. Cross sections of different joint types.

Airfield pavement joints for facilities serving aircraft larger than 100,000 lb (45,360 kg) fall into three categories: construction, contraction and isolation.[1][2] Figure 2 on the next page provides typical pavement joint details and dimensions.The engineer and contractor must fully under­stand the purpose of these joints in order to properly specify them on the plans and build them in the field.

Isolation Joints – The purpose of an isolation joint is to separate intersecting pavements and to isolate embedded fixtures within the pavement (pavement penetrations), such as in­pavement drains. Figure 2, Type A shows stan­dard isolation joint details.

Type A thickened edge isolation joints do not use dowel bars, but use increased thickness along the joint to reduce tensile stresses in the slab and bearing stresses on the subbase or subgrade. Type A undoweled isolation joints allow the pavement freedom of movement laterally and an embedded fixture freedom of movement vertically, with no mechanical interconnection. Separation with each provided with a non­extruding compressible material.

Contraction Joints – Contraction joints control the loca­tion of pavement cracking caused by drying shrinkage and/or thermal contraction. Contraction joints also are used to reduce the stress caused by slab curling and warping. Load transfer usually is accomplished by aggre­gate interlock. However, dowel bars may be used for load transfer at contraction joints under certain conditions. Figure 2, Types B, C and D show standard contraction joint details.

Construction Joints – Construction joints separate abut­ting construction placed at different times, such as at the end of a day’s placement, or between paving lanes. Load transfer at construction joints is achieved through the use of dowel bars. Figure 2, Type E shows a standard construc­tion joint detail.

Isolation Joint Considerations

When joints are designed according to the recommenda­tions of this guide, isolation joints are not required trans­versely or longitudinally in airfield pavements except at special locations. Introduction of “expansion” joints on a regular spacing tends to allow slabs to migrate because contraction joints in interior areas of a concrete pavement open unnecessarily. This unintended consequence degrades the effectiveness of aggregate interlock at the contraction joints and reduces the overall performance of the pavement. Thus, the traditional and misleading term “expansion” joint has been modified to “isolation” joint to be more accurate and descriptive and the FAA no longer recommends the use of “expansion” joints.

The purpose of an isolation joint is to separate intersecting pavements or to isolate structures within or along the pavement. Isolation joints provide freedom for lateral panel movement without any mechanical interconnection that might damage the pavement, structure or fixture (see the section titled “Pavement Penetrations”). To be effec­tive, the pre­molded compressible filler should meet the requirements of ASTM D1751, D1752, or D994, and must cover the entire depth of the concrete slab.

If an isolation joint is placed within the pavement area and will carry active traffic loads (such as where the pavement abuts a structure like a building) or where horizontal and vertical differences in movement of the pavements are anticipated, a thickened edge isolation joint (Type A – Thickened Edge) is necessary to reduce edge stress in the pavement. If the isolation joint is used along a pavement penetration, building or other non­load area, then a simple butt joint (Type A – Undoweled) typically is required.

All intersections of runway, taxiway, or apron pavements require a thickened edge isolation joint (Type A – Thick­ened Edge) to separate the facilities, which expand and contract along different axes. The concrete panels on both sides of the joint are thickened by 25 percent. The thick­ened edges are tapered back to the nominal thickness over at least 10 ft (3 m) but it is preferable to taper the thickness over the length or width of a full panel.

Longitudinal Joint Considerations

Figure 3. Overhead view of the paving of alternate lanes on both apron and taxiway pavement. Each longitudinal edge forms a longitudinal construction joint.

Longitudinal joints are those joints parallel to the lanes of construction and usually the direction of traffic. They are either contraction joints (Type B, C, or D) that are sawed between the construction joints or construction joints (Type E) that are formed as the edges of construction lanes (Figure 3). If the new pavement is placed adjacent to and abutting an existing concrete pavement, then the longitu­dinal joint at, or near, the interface also might need to be an isolation joint (see the section titled “Jointing Arrange­ments”).

Longitudinal Joint Spacing – The pavement thickness and the overall width of the pavement feature (runway, taxiway or apron) are the primary factors determining the spacing of longitudinal joints. A longitudinal joint spacing that divides the pavement section evenly is most advanta­geous, reliable and recommended. For example, 37.5 ft (11.5 m) wide construction lanes can be used with inter­mediate longitudinal contraction joints at 12.5 or 18.75 ft (3.8 or 5 .7 m), depending upon pavement thickness.

In some cases, it is advantageous to select a longitudinal joint spacing that will facilitate construction using the available paving equipment. Unlike years ago when equip­ment choices were limited, modern slipform paving equip­ment permits construction widths up to 50 ft (15 .2 m). While this permits the designer and contractor greater flexibility to satisfy specific situations, a uniform spacing is always recommended.

The spacing of longitudinal (and transverse) joints also depends upon shrinkage properties of the concrete, soil conditions, subbase materials, climatic conditions, and slab thickness. Table 1 lists the Federal Aviation Administration (FAA) recommended maximum longitudinal joint spac­ings for concrete pavements built on unstabilized (gran­ular) or stabilized subbases. Panels kept to dimensions shorter than the lengths listed in Table 1 (next page) will have curling and warping stresses within acceptable limits and minimal risk of uncontrolled cracking.

The radius of relative stiffness is defined by Westergaard as the stiffness of the slab relative to the stiffness of the foun­dation. It is determined by the following formula:

(Eq. 1)


where:

l= radius of relative stiffness, in. (mm)

E = modulus of elasticity of the concrete, psi (MPa)

h = slab thickness, in. (mm)

k = modulus of subgrade reaction, psi/in. (MPa/m)

µ = Poisson’s ratio for concrete, usually 0.15

The radius of relative stiffness has the dimension of length. When the radius of relative stiffness is divided into the slab length (L), the dimensionless result is the L/l ratio.

An L/l ratio of 7 has been shown by field performance to adequately control cracking and reduce the risk of uncon­trolled cracking on pavements placed on stabilized foun­dations, including existing pavements for overlays, under certain conditions. It is difficult to determine the radius of relative stiffness reasonably in the design stage, because the Modulus of Elasticity of the concrete is unknown and will vary significantly depending upon the concrete mixture, and the actual k­value in the field is yet to be determined.[3] Thus, the FAA’s current recommendations are based on a conservative ratio of joint spacing to radius of relative stiffness of 5.(1)

Table 1. FAA Recommended Maximum Joint Spacing(1).

Concrete Pavement on an Unstabilized (Granular) Subbase
Slab Thickness Maximum Longitudinal Joint Spacing Maximum Transverse Joint Spacing
6 in. (150 mm) 12.5 ft (3.8 m) 12.5 ft (3.8 m)
7-9 in. (175-230 mm) 15 ft (4.6 m) 15 ft (4.6 m)
>9 in. (230 mm) 20 ft (6.1 m) 20 ft (6.1 m)
Pavement on a Stabilized Subbase
Slab Thickness Maximum Longitudinal Joint Spacing Maximum Transverse Joint Spacing
8-10 in. (203-254 mm) 12.5 ft (3.8 m) 12.5 ft (3.8 m)
11-13 in. (279-330 mm) 15 ft (4.6 m) 15 ft (4.6 m)
14-16 in. (356-406 mm) 18.75 ft (5.7 m) 17.5 ft (5.3 m)
> 16 in. (406 mm) 20 ft (6.1 m) 20 ft (6.1 m)




Load Transfer at Longitudinal Joints – The following is a guide to determining longitudinal joint load transfer:

  • All longitudinal construction joints should be Type E doweled joints (unless they serve as an isolation joint).
  • For runways and aprons, which are typically wide pavement areas, undoweled joints (Type D) are acceptable for intermediate longitudinal contraction joints, unless the joint is one of the last three joints before a free edge or isolationjoint. For this exception a doweled joint (Type C) is recommended.
  • For all narrow taxiway pavements[75 ft(23 m)or less] on unstabilized (granular) subbases, and thinner than 9 in. (230 mm), tied joints (Type B) are acceptable for intermediate longitudinal contraction joints.
  • For taxiway pavement greater than 9 in. (230 mm), doweled joints (Type C) are required in intermediate longitudinal contraction joints adjacent to a free edge.

For pavement carrying wide­bodied aircraft in channelized traffic areas, dowel bars are preferred over tiebars because they strengthen the joint and provide better mechanical load transfer. Aprons and runways are not as critical as taxi­ways because these features are typically wide pavement features and joints within their interior are held tight by the mass of surrounding pavement. However, when the intermediate longitudinaljoint is the lastjoint before a free edge, mechanical load transfer becomes more important for long­term pavement performance.

Keyways – Keyed construction joints should not be used in airfield pavements. Experience on airfield pavements with keyed longitudinal construction joints shows that the keyways provide limited strength and often break, becoming a maintenance problem.[4] Keyways perform particularly poorly if they are either too high or too low in the slab. The female side of the key often cracks to the pavement surface, creating a small sliver of loose concrete. Over time, failed keyways break into small fragments, which results in a high potential for foreign object damage (FOD).

Transverse Joint Considerations

Transverse contraction joints (Type C or D) create a weak­ened plane at planned locations perpendicular to the direction of paving in order to control where cracks form. Sawing the pavement creates transverse contractionjoints and the saw kerf depth for contraction joints is most effec­tive if it is at least one­fourth of the slab thickness*. For concretes made with hard aggregates and for pavement constructed on stabilized subbase, a saw kerf of one­third the thickness of the pavement is most effective.

-The Federal Aviation Administration’s current recommenda­tion is for a saw cut depth of one­fourth the pavement thick­ness.[5] Experience shows that saw cuts to one­fourth the pavement thickness are effective under moderate prevailing paving conditions. Increasing the depth of cut to one­third the pavement thickness where hard aggregates or a stabilized subbase are used, as recommended by this guide, provides increased control against the development of uncontrolled (random) cracking.

Note: The dowel sizes here are in the correct proportion to the load for which the pavement is designed. Because the pavement thick­ness is in proportion to anticipated loads, dowel size and spacing requirements also relate to pavement thickness. Condition surveys of existing pavements and extensive tests on full­scale slabs have shown no clear cases of dowel failure where the pavement slab itself is adequate for the loads carried.

Joint Spacing – Table 1 lists the FAA recommended maximum transverse joint spacings for concrete pave­ments built on unstabilized (granular) or stabilized subbases. It should be noted, however, that the climate and concrete aggregate common to some geographic regions may allow transverse joints to be further apart, or require them to be closer together than listed in Table 1. For example, concrete made from granite and limestone coarse aggregate is much less sensitive to temperature change than concrete made from siliceous gravel, chert, or slag aggregate. A less temperature­sensitive concrete does not expand or contract much with temperature change, which allows a longer spacing between pavement contraction joints without any greater chance of random cracking. However, unless experience with local conditions and concrete aggregates indicates otherwise, use the values in Table 1 as the maximum allowable transverse joint spacing for plain concrete airfield pavements.

Aspect Ratio Limit – Performance has shown that it is desirable to have panels with approximately equal trans­verse and longitudinal joint spacing. When slabs are long and narrow, they tend to crack under traffic into smaller pieces of nearly equal dimensions, as is alluded to in Table 1. Panels are not likely to develop an intermediate crack if the length­to­width ratio does not exceed 1.25 . This ratio may be difficult to maintain within intersections and can be disregarded in favor of common­sensejointing patterns (see the section titled “Odd­ Shaped Panels”).

Butt Joints – Transverse construction joints are neces­sary at the end of paving each day or where paving opera­tions are suspended for 30 minutes or more. If the construction joint occurs at or near the location of a trans­verse contraction joint, a doweled butt joint (Type E) is recommended. A construction joint occurring in the middle of the normal joint interval should not be used unless the pavement is cut back to normal joint spacing.

Dowel Bars

Dowel bars (or dowels) are used to transfer wheel loads across a joint to the adjacent panel, reducing deflection (and stress) at the joint and preventing differential displacement of the abutting panels. Dowel bars are smooth bars that must be placed near the neutral axis (mid­depth) of a slab and in careful alignment to allow adjacent slabs to move when expanding or contracting from thermal changes.

The need to use dowels depends upon the joint type and its location in the airfield pavement facility. The following joints require dowels:

  • All butt­ type construction joints
  • Transverse contraction joints near the free edges of a facility, such as a runway or taxiway.

Dowels are not required at transverse contraction joints unless the joint is near a free edge or an isolation joint. The reason they are required in transverse contraction joints near the free edges of facility is because thermal move­ments result in permanent opening of transverse joints for a distance of about 100 ft (30.5 m) back from a free edge. Likewise, thermal movements result in permanent opening of transverse joints for a distance of about 60 ft (18.3 m) to either side of an isolation joint. The transverse joints within these distances gradually open to a point where aggregate interlock is less effective. Therefore, a doweled contraction joint (Type C) should be used for the last three transverse contraction joints at the end of a runway, taxiway, or apron.

Recommended sizes and spacing of dowel bars are provided in Table 2.

Table 2. Dimensions and Spacing of Smooth Steel Dowel Bars.

Slab Thickness Dowel Diameter Dowel Length Spacing Between Bars
6-7 in. (150-180 mm) 3/4 in. (20 mm) 18 in. (460 mm) 12 in. (305 mm)
8-12 in. (210-305 mm) 1 in. (25 mm) 19 in. (480 mm) 12 in. (305 mm)
13-16 in. (330-405 mm) 11/4 in. (30 mm) 20 in. (510 mm) 15 in. (380 mm)
17-20 in. (430-510 mm) 11/2 in. (40 mm) 20 in. (510 mm) 18 in. (460 mm)
21-24 in. (535-610 mm) 2 in. (50 mm) 24 in. (610 mm) 18 in. (460 mm)
Note: The dowel sizes here are in the correct proportion to the load for which the pavement is designed. Because the pavement thick - ness is in proportion to anticipated loads, dowel size and spacing requirements also relate to pavement thickness. Condition surveys of existing pavements and extensive tests on full-scale slabs have shown no clear cases of dowel failure where the pavement slab itself is adequate for the loads carried.


Satisfactory joint performance is directly dependent upon the alignment and position of dowels. The installation requirement depends upon the joint type:

Figure 4. Dowel drilling rig for longitudinal joints.
Figure 5. Dowel baskets fastened in place ahead of slipform paver.
  1. In longitudinal construction joints (or transverse for some cases), dowel bars typically are installed by drilling into the edge of a panel or panels. For drilling into the concrete, contractors employ gang­mounted hydraulic or pneumatic drill rigs to assure proper alignment (Figure 4). The bars are inserted into the drilled holes after high strength cement grout or epoxy is placed into the back of the drilled hole. The purpose of the cement or epoxy is to assure that the annular space between the concrete and the dowel is filled so that loads applied to concrete are imparted directly to the dowel. The exposed ends of the dowel are oiled to allow movement in the abutting concrete. Grease is not used because it will allow for the forma­tion of a large annular space around the dowel.(When fixed­form pavement construction techniques are used, the contractor may elect to insert the dowel through holes in a bulkhead form or fixed side form).
  2. In transverse contraction joints, dowels typically are mounted in a wire cage or basket, which is firmly anchored to the subbase, to hold the dowels in posi­tion and alignment (Figure 5). Contraction joint dowel assemblies are fastened to the subbase using steel staking pins for unstabilized(granular)subbases or nailing clips for stabilized subbases. Care in posi­tioning the baskets is necessary so that the dowels align parallel to the longitudinal joints (longitudinal axis of the pavement.) A permanent mark or colored nail indicating the location of the dowel baskets is necessary for reference when later sawing the contraction joints.
As an alternate to placement of contraction joint dowels in basket assemblies, automatic dowel inser­tion equipment may be used. The key to controlling the location and positioning of inserted dowel bars is the concrete mixture. Well­graded mixtures produce excellent results with dowel insertion, while gap­graded mixtures tend to allow the dowels to migrate within the concrete mass during construction.

A 3% or 3/8 in./ft (3 mm/100 mm) tolerance from true alignment is acceptable for horizontal and vertical align­ment of dowels. A minimum embedment length of 6 in. (150 mm) on either side of the joint is required to obtain effective load transfer.

To ensure that dowels do not bond to concrete panels and restrain the panels during thermal expansion or contrac­tion, each dowel requires a coating of form release oil or a factory­applied debonding agent. Factory­applied debonding agents include paraffin and epoxy­based mate­rials, which reduce the frictional resistance of a dowel embedded in concrete without a coating of oil. These debonding materials are applied directly over corrosion­resistant dowel coatings, such as paint or epoxy. It is advis­able to ensure that all dowel coatings are certified or tested according to AASHTO T253 and AASHTO M254, and compared to the results of a control test of a similar bar coated only with form release oil. Materials exceeding the results of the control dowels provide adequate reduction in dowel/concrete friction.

Tiebars

Tiebars are deformed steel bars. They are rarely used in airfield pavements that serve aircraft larger than 100,000 lb (45,360 kg). Tiebars should not be used to “tie” together panels of pavement features built on stabilized subbases because doing so increases restraint to pavement move­ment from thermal changes, and the likelihood of cracking in the panels due to the restraint stresses.

Tiebars are not load­transfer devices. Aggregate interlock provides the load transfer function in contraction joints that include tiebars. The purpose of the tiebars is to hold the panels tightly together to maintain aggregate inter­lock.

The nominal diameter, length and spacing of tiebars for airfield pavement are:

  • Diameter: 5/8 in. (16 mm)
  • Length: 30 in. (760 mm)
  • Spacing between tiebars: 30 in. (760 mm)

Placement tolerances for tiebars are not as critical as for dowel bars because the purpose of the deformed tiebars is to prevent joint opening. (Some misalignment of the tiebars is actually beneficial mechanically.) It is sufficient for the contractor to place the tiebars reasonably perpen­dicular to the tied joint. Mechanical insertion equipment, and rigidly secured chair systems also provide adequate results.

Jointing Arrangements

Figure 6. Typical jointing arrangements for concrete airfield pavements.

Figure 6 on the next page shows typical jointing arrange­ments for airfield pavements. It is important that the engi­neer responsible for laying out the joints as a part of the pavement design become familiar with construction equipment and techniques used in airport pavement construction.

Construction joints generally should be placed parallel to the longest length of a pavement feature. This orientation generally ensures the most efficient construction by means of fixed­form or slipform methods. The layout for taxiways and runways is not difficult in this regard. However, apron pavements represent unique challenges for maximizing construction in the direction of traffic and minimizing hand placement.The engineer should consider the efficiency of construction when selecting the joint orientation for apron pavements.

The layout of joints at airfield pavement intersections also presents special jointing challenges. Intersections create large, irregularly­shaped areas of pavement and introduce the need to intersect different types of joints. It is virtually impossible to establish a standard joint pattern for inter­sections. However, the designer may select from well­established options and follow sound principles to simplify joint layout and avoid problematic designs.

ISOLATING INTERSECTIONS:

  • Provide an undoweled, thickened­edge isolationjoint (Type A) between intersecting pavements. The abut­ting edges of both pavements are thickened 25 percent at the joint. Joint location and type does not need to match across an undoweled isolation joint because there is no connection and little chance of sympathy cracking. The three contraction joints on either side of the isolation joint require dowels to provide load transfer in case the joints open.
  • Provide an undoweled, thickened­edge isolationjoint (Type A) between new pavement and an existing paved area (Figure 6 on the next page).

PRINCIPLES FOR JOINT LAYOUT:

  • In the fillet areas, align the last 3 ft (1 m) of all joints perpendicular to the perimeter edge of the pavement and along a radial line.
  • Avoid layout patterns that create acute angles less than 60 degrees. Regardless of the situation, creation of small acute angles will increase the risk of cracking in areas of fillets and curves.
  • In areas where a fillet begins and ends, avoid creating

a slab less than 2 ft (0.6 m) wide. For more information on jointing intersections see ACPA’s IS006P,“Intersection Joint Layout.”

Odd­Shaped Panels– The odd­shaped panels that result in the fillet areas where pavements intersect require the use of embedded steel. Cracks may form in odd shaped panels and those cracks could become the source of debris that is particularly undesirable for airfield pavements. Spalling along the cracks increases the risk of FOD.To mini­mize the risk, embedded steel is recommended. A steel quantity of 0.05 percent of the cross­sectional area in both directions is adequate for slabs where the length­to­width ratio exceeds 1.25 or in slabs that are not rectangular in shape. For more information on using embedded steel, see the section titled “Embedded Steel.”

Figure 7. Options for fillet areas at airfield pavement intersections.

Alternative to Fillets – Instead of building fillets into the pavement, an option is to paint the fillets. This option requires building full-­sized panels in the fillet area (Figure 7). A paint stripe defines the fillet and the unused portion of the slab is painted to represent a non­traffic area.

Figure 8. Details for pavement penetrations(boxouts).

Pavement Penetrations – Pavement penetrations typi­cally require a perimeter isolation joint to allow free move­ment of the fixture or panel. In airfields, pavement penetrations are common for fixtures such as drainage inlets and in­pavement lighting. There are a variety of joint layout options for creating the necessary separation between the two elements that will allow them to move freely with temperature cycles and seasonal heaving or settling. The most common is the “boxout” (Figure 8).

An isolation joint (Type A ­Undoweled) typically is accept­able for the boxout perimeter, which can be square­, round­or diamond­shaped. Common square boxouts sometimes cause cracks to form at the boxout’s corners.To avoid crack­inducing corners, the designer can consider using rounded boxouts or placing fillets on the corners of square boxouts. It is advantageous to place welded­wire fabric or small­diameter reinforcing bars in the concrete pavement around any interior corners at square boxouts to hold cracks tightly should they develop. Diagonal boxouts can eliminate the interior corners that might induce cracks, but they must be laid out carefully to ensure they are in the proper location.

Figure 9. Light cans in place prior to paving. Note the reinforcing bars around the light cans to reinforce the area and to serve as a precaution to hold any cracks together.

Some fixtures, such as light cans, may not require a boxout with perimeter isolation and can be cast directly within the concrete (Figure 9).The fixtures may be wrapped with flex­ible, non­extruding isolation joint filler.The height of these fixtures must be below the pavement surface elevation to allow the paving machine to pass over them during construction; workers expose the fixtures just after paving. More detailed information about light cans is available in the section titled “In­ Pavement Lighting Considerations.”

File:Airjoint10png
Figure 10. Design details for juncture between concrete and asphalt pavement for specialty situations.

Placements Adjacent to Asphalt Pavement – Experi­ence shows that under aircraft traffic, objectionable rough­ness may develop in the asphalt near the juncture of concrete and asphalt pavements.[6] Figure 10 provides details of a buried slab design to minimize the roughness at such a transition. This detail is used for critical traffic areas and where even slight deviations from the design grade are objectionable, such as:

  • All junctures in a transverse direction in runways
  • All junctures between runways and taxiways
  • All junctures in channelized traffic areas

A buried slab detail is not considered necessary between non­channelized traffic areas (non­primary taxiways, etc.) and pavement areas such as parking, service and mainte­nance aprons, except under unusual circumstances; a simple butt­faced joint with a thickened concrete pave­ment edge is acceptable for these areas.

If a new concrete pavement will adjoin an existing asphalt pavement in a channelized area, the existing asphalt pave­ment must be modified to accommodate this transition joint. The existing asphalt pavement is cut back cleanly with a saw 10 ft (3.25 m) from the planned junction loca­tion. The material is removed to accommodate the buried slab.The asphalt beyond the 10 ft (3.25 m) perimeter is left undisturbed.

Apron Consideration – Aprons, which typically are wide expanses of pavement carrying mostly non­channelized, slowly moving traffic, are usually very unique in geometry to the airfield. Joint design considerations will be unique to the airfield; however, a few consistent principles apply to these features. Interior longitudinal and transverse contraction joints are undoweled because the large mass of pavement holds these joints tight, allowing aggregate interlock to provide effective load transfer. Aprons should be isolated from buildings, taxiways, and airfield mainte­nance pavements to prevent cracking, heaving and other problems associated with undesirable mechanical inter­connection.

To prevent separation ofjoints and migration of the panels along the perimeter of apron pavements, a tension ring design was recommended by the industry and many spec­ifying agencies prior to the 1950’s. At that time, apron designs included unstabilized(granular)subbase materials underneath the concrete pavement. Unstabilized (gran­ular) subbase materials provide low coefficient of friction to resist slab sliding. The tension ring was created by using deformed tiebars in the last longitudinal construction or contraction joint surrounding the perimeter of the facility.

Figure 11. Conceptual illustration of apron jointing for facilities serving 100,000 lb (45,360 kg) aircraft on stabilized subbases, in lieu of traditional tension ring used for aprons supported by low-friction unstabilized (granular) subbase materials.

Today, designs for facilities serving aircraft greater than 100,000 lb (45,360 kg) typically require stabilized subbases and these subbase materials provide higher frictional resistance to slab migration. The traditional tension ring using deformed tiebars is no longer necessary to prevent slab migration and hold interior joints tight. Now, an effec­tive design for apron pavements supported by stabilized subbase materials includes doweled longitudinal construction or contraction joints surrounding the perimeter of the facility (Figure 11). The dowel bars are used as a precaution to maintainjoint performance in case some opening of the perimeter joints might occur.

Sealing Joints

Joint sealants are used in airfield pavement joints to keep out incompressible material and to minimize infiltration of water. To perform well, sealant materials must be capable of withstanding repeated extension and compression as the pavement slabs expand and contract with temperature and moisture changes. The size and shape of the sealant cross­section affects the sealant material performance.

Figure 12. Joint sealant reservoir design options for airfield pavements.

Figure 12 shows common sealant configurations for airfield pavements. In refueling locations and any airfield pavement area subject to fuel spillage, jet fuel resistant sealants are necessary.

*Basic information on the technology of joint sealing and sealants can be found in other ACPA publication, such as TB012P, “Joint and Crack Sealing and Repair for Concrete Pavements.”

Embedded Steel

Under most circumstances, airfield concrete pavements are designed as plain pavements, containing steel only at pavement penetration areas and in odd­shaped panels. Embedded steel is not intended to add to the structural capacity of a pavement. The thickness required for pave­ment locations including embedded steel is the same as required for plain pavement. The purpose of the steel is to keep any cracks that may develop in concrete panels from separating and becoming a source of debris. By holding structural cracks tight, embedded steel also improves load transfer through aggregate interlock. Embedded steel is not necessary where the pavement isjointed to form panel lengths and shapes that will control intermediate cracking and limit transverse contraction joint opening.

Embedded Steel Design – Embedded steel in jointed concrete pavements can be welded­wire fabric or bar mats. The steel is discontinuous (i.e., does not extended across transverse or longitudinal joints). Steel in the form of smooth dowel bars also is used in somejoints, as discussed previously.

Experience shows an effective quantity of steel for airfield pavement is between 0.05 and 0.3 percent of the cross­sectional area of pavement. The nominal minimum amount of steel (0.05%) is usually acceptable for odd­shaped panels. In special circumstances, more steel may be considered necessary. The nominal maximum amount of steel (0.3%) was found to be effective for jointed rein­forced pavements in the 1970’s.[7] Pavements with less steel than the minimum will not perform well because eventually the steel may corrode, rupture and no longer hold together the fractured faces of mid­panel cracks. The cracks then may become filled with incompressible mate­rials and lose aggregate interlock and load transfer. The seriousness of this load transfer degradation depends upon the degree of support provided by the subbase and subgrade. The type and amount of aircraft traffic is also a factor. After a crack becomes filled with incompressible material, it may spall and become a source of FOD that may damage jet engines.

Do not decrease the design thickness of slabs containing steel to offset the cost of adding the embedded steel. Embedded steel does not increase the pavement’s flexural (bending) strength. Because the steel is typically placed near a plane extending through the middle of the pave­ment section (along the neutral axis), it is not in a zone of high tensile stress during slab bending. Furthermore, 0.05 to 0.3 percent steel by cross­sectional area is not enough steel to significantly alter the tensile capacity of the concrete.

Because the purpose of embedded steel is to keep cracks tightly closed, it must have sufficient strength to hold two concrete panels together during contraction. The required strength is equal to the force necessary to overcome the resistance between the pavement and subbase or subgrade that is developed over a distance from the crack to the nearest joint, crack or edge of panel. This force increases with the distance over which resistance is devel­oped. The force is greatest at the middle of a panel, but for design practicality, the same steel quantity is used throughout a panel.

Equation 2, based on the subgrade drag theory, computes the steel percentage required for a given concrete pave­ment design with embedded steel. The computation includes the influence of the weight of the concrete panel, the coefficient of subgrade or subbase resistance, and the tensile strength of the steel.

As = LCfwh / 24 • fs (English) (Eq. 2)

As = LCfwh / 204.1 • fs (Metric)

where:

As = area of steel required per ft (m) slab width, expressed in in.2 (mm2)

L = distance to nearest free (untied) joint or pavement edge for transverse steel (or distance between trans­verse joints for longitudinal steel), ft (m)

Cf = coefficient of subgrade or subbase resistance to panel movement

w = weight of concrete, lb/ft3(kg/m3) [use 150 lb/ft3(2400 kg/m3) for normal­weight concrete]

h = slab thickness, in. (mm)

fs = allowable tensile stress in the steel, psi (MPa); usually taken as 2/3 of the yield strength

The resistance coefficient, Cf, is sometimes referred to as the coefficient of friction between the slab and subgrade or subbase. The situation is more complex than pure sliding friction because shearing forces in the subgrade or subbase and warped slabs may be involved in the resist­ance. For subgrades and unstabilized (granular) subbases, coefficients of resistance range from 1 to 2, depending on type of material and moisture conditions. Coefficients for stabilized subbases are much greater (asphalts range from 5 to 15, while lean concrete subbases(LCB)range from 8 to 15). Research indicates that the coefficient also varies with respect to panel length and thickness. Even though Equa­tion 2 accounts for friction, use of a Cf higher than 1.5 has not been justified by pavement performance. While the subgrade drag theory requires more steel as the frictional resistance at the slab and subgrade or subbase interface increases, it is important to consider that in the field panels are less likely to separate on subbases that provide higher friction resistance. Thus, further research currently is being conducted to better define this relationship.

- Continuously reinforced concrete (CRC) pavements require as much as 0.7% steel to alter the crack pattern developed in concrete pavement. Most CRC design procedures do not recommend decreasing the design thickness of concrete pave­ment to account for any improved bending strength provided by the high percentage of reinforcement. Because jointed reinforced pavement uses a much lower percentage of steel, the steel is even less influential on slab bending strength.

Table 3. Yield Strengths of Various Grades of Steel

ASTM Designation Type and Grade of Steel Yield Strength psi (MPa) Allowable Tensile Stress psi (MPa)
A615 Deformed Billet Steel, Grade 40 40,000 (280) 27,000 (190)
A616 Deformed Rail Steel, Grade 50 50,000 (350) 33,000 (230)
A616 Deformed Rail Steel, Grade 60 60,000 (420) 40,000 (280)
A615 Deformed Billet Steel, Grade 60 60,000 (420) 40,000 (280)
A185 Cold Drawn Welded Steel Wire Fabric 65,000 (460) 43,000 (300)
A497 Cold Drawn Welded Steel Deformed Steel Wire 70,000 (490) 47,000 (330)


Table 4. Dimensions and Unit Weights of Deformed Steel Reinforcing Bars

Bar Size No. Diamter in. (mm) Area in2 (mm2) Perimeter in (mm) Unit Weight lb/ft (kg/m)
3 (10M) 0.375 (9.5) 0.11 (0.71) 1.178 (300) 0.376 (0.56)
4 (13M) 0.500 (12.7) 0.20 (1.29) 1.571 (400) 0.668 (1.00)
5 (16M) 0.625 (15.9) 0.31 (2.00) 1.963 (500) 1.043 (1.57)
6 (19M) 0.750 (19.1) 0.44 (2.84) 2.356 (600) 1.502 (2.26)
7 (22M) 0.875 (22.2) 0.60 (3.86) 2.749 (700) 2.044 (3.07)




- Nominal Dimensions

The allowable working stress in the steel, fs, depends upon the type of steel. Table 3 provides yield strengths and corresponding allowable tensile stresses based on typical current steel manufacturing specifications.

Where the spacing between free longitudinal joints is sufficiently close to control intermediate cracking, less transverse steel is required than computed by Equation 2. The transverse steel only serves to hold any longitudinal steel in position during construction.

Selection of Steel Size and Spacing – Table 4 lists the dimensions and unit weights of standard reinforcing bars.

Manufacturers of welded­wire fabric provide tables on their products denoting styles for different applications. The tables give diameter and spacing of wire in US customary units for both longitudinal and transverse direc­tions as well as weight per 100 ft2, and per 1 yd2, for each style. Metric (SI) sizes also are available. Consult the manu­facturer’s product literature or Internet web site for styles of welded­wire fabric suitable for airfield concrete pave­ment†.

†Welded­wire fabric requires extra design considerations to ensure the design is economical. The choice of smooth welded­wire fabric or deformed welded­wire fabric depends upon the difference in allowable design stresses, the availability of desir­able sizes, and cost. The minimum sizes for airfield concrete pavement are W5 or D5 for longitudinal wire and W4 or D4 for transverse wire. The fabric size chosen for a project must meet the minimum steel percentage of 0.05. This minimum percentage is based on steel having a 65,000 psi (460 MPa) yield strength. If the fabric is made from steel with a lower yield strength, more steel and a different wire size and spacing is required. To produce the most economical design it is better to select a standard size of welded­wire fabric. Special orders can be made for non­standard welded­wire fabric, but the cost is higher. Also, welded­wire fabric sheets in excess of standard widths likely will cost more for fabrication and shipping.

To determine the size and spacing of steel to use in bar mats, select a standard deformed steel bar meeting an ASTM standard dimension that will produce a practical spacing. The area of steel required, As, as determined from Equation 2 or by multiplying the required percentage of embedded steel (such as the minimum 0.05 percent) by the area of concrete per unit length (or width), is divided by the area of the standard bar to obtain the number of bars required per length (or width). The engineer is cautioned to select a spacing between bars that is less than about 12 in. (300 mm) in order to ensure good steel distribution and limit crack widths.

Installation of Embedded Steel – Because embedded steel is not intended to act in flexure, its position within the slab is not crucial to performance, except that it should be adequately protected from corrosion with a minimum concrete cover of 2 in. (50 mm). However, experience seems to indicate that embedded steel remains most effective at keeping cracks tight, if it resides at a depth between 0.3T and 0.5T from the pavement surface. If the steel is slightly below mid­depth, pavement performance is generally not effected unless the steel is within the bottom third of the slab.When steel is too low in a slab, it is prone to corrosion and is relatively ineffective at holding cracks tight and preventing the intrusion of incompress­ible material during curling and warping cycles.

Plans or shop drawings typically specify placement of embedded steel reinforcing bars near mid­depth of the slab. Plans also require embedded steel to be discontinued at transverse and longitudinal joints; a gap of 2 to 6 in. (50 to 150 mm)ensures that thejoint can function properly.To avoid joint formation and performance problems, designers and contractors should not place embedded steel across any transverse joint in a jointed pavement design.

Some overlap of welded­wire fabric sheets or bar mats may be necessary if the reinforcement panels are smaller than the concrete panels. End laps should be a minimum of 12 in.(300 mm) and no less than 30 times the diameter of the longitudinal wire or bar. Side laps should be a minimum of 6 in. (150 mm) and no less than 20 times the diameter of the longitudinal wire or bar.

Figure 13. Jointing of concrete airfield pavement panels with embedded steel.

Clearance between the embedded steel and the edges of a slab also is important to ensure the steel is adequately protected from corrosion. End and side clearances should be a minimum of 2 in.(50 mm)and a maximum of 6 in.(150 mm)to provide nearly complete distribution without sacri­ficing concrete cover surrounding the steel. A distance between longitudinal members of 4 to 12 in. (100 to 300 mm) and a distance between transverse members of 4 to 24 in. (100 to 600 mm) also is recommended. Figure 13 shows details of jointing concrete airfield pavement panels with embedded steel.

Jointing with Stabilized Subbases

The main functions of the subbase layer in a concrete pavement structure include providing a stable construc­tion platform, providing uniform support, preventing pumping, and reducing frost effects.[8] The subbase stiff­ness can have a profound effect on the required panel size and can be a direct contributor to good performance or to performance deficiencies.

In concrete pavements, the concrete distributes applied loads over a large area; therefore, high­strength subbases typically are not necessary. In fact, a uniform, durable, non­erodible subbase material is often preferable to a high­strength subbase material in concrete pavement structures for most vehicles.[9]

However, a well­designed and constructed stabilized subbase layer provides some benefit to airfield pavements for heavy aircraft. A stabilized subbase provides extra support for heavy aircraft gear loads and ensures good load transfer across the joints, which reduces the potential for load­related cracking and faulting, and fosters long­term pavement performance.

The FAA’s AC 150/6320­6E requires a stabilized subbase layer for all new concrete pavements designed for aircraft weighing 100,000 lb (45,360 kg) or more. These stabilized subbases can consist of CTB, econocrete/LCB, or asphalt­treated subbase (ATB). For stabilized subbases, the modulus of subgrade reaction (k­-value) is increased by a factor proportional to the subbase thickness. The maximum k­value allowed in AC 150/5320­6E is 500 psi/in. (136 MPa/m) because this value is the highest k­value that can be accurately measured in the field. Exceptions to the stabilized subbase requirement may be made on the basis of superior materials being available, such as 100 percent crushed, hard, closely graded stone.These materials should exhibit a remolded soaked CBR minimum of 100.

Early-Age Considerations – Research indicates that a well designed and constructed stabilized subbase coupled with an adequate jointing arrangement helps concrete pavements for heavy aircraft achieve their long­term performance goals. However, when the primary function of the stabilized layer is misconstrued by the engineer or contractor, deficiencies such as early aged cracking can result. Examples of misapplications include[10]:

  • Increasing stabilized subbase thickness to reduce concrete layer thickness.
  • Increasing stabilized subbase strength to achieve construction expedience.
  • Selecting panel sizes based on past joint spacing practices without considering the impact of the stiff­ness of the stabilized subbase.

To better ensure successful construction of concrete pave­ment on stabilized subbases, engineers and contractors must address the factors that contribute to good perform­ance of joints and slabs.

Of primary concern are forces that induce movements in young concrete and factors that aggravate the impact of these movements on stress development in the pave­ment. For purposes of the discussion herein, driving forces are call “triggers” and the aggravating factors are called “variants”.

Triggers are associated primarily with ambient conditions during placement of concrete and are mostly out of the control of the engineer or contractor, while variants are key design, materials, and construction properties of the stabi­lized subbase and concrete. When a variant exceeds its threshold level, the risk of early­age cracking is elevated. One common design variant that is known to contribute to underperforming pavement is concrete panel sizes that are too large relative to the subbase stiffness and/or slab thickness. The concept of controlling variants must be considered by the engineer during the design phase, while developing the jointing arrangement or layout plan. The most common variants that affect performance include:

  • Subbase strength/stiffness.
  • Joint sawing/timing.
  • Panel sizes and aspect ratios.
  • Concrete/subbase interface friction.
  • Cementitious factor of the concrete mixture.
  • Panel sizes and aspect ratios.
  • Presence of absence of bond­breaker.
  • Curing procedures.
  • Shrinkage susceptibility of concrete mixtures.
  • Subbase thickness.
  • Presence of shrinkage cracking in the subbase.
  • Internal slab restraint (i.e., dowel bars, tiebars, etc.).
Figure 14. Risk assessment of early-age cracking in concrete airfield pavement built over stabilized subbase (after ref. 6). 17

Risk Assessment – Figure 14 summarizes the various triggers and their threshold values, and quantifies the risk of underperforming pavement as a combination of factors. Note that the existence of just one trigger and one variant may be enough to cause distress. The risk of early distress increases as more triggers and/or variants exceed their threshold and affect a project.

Using Figure 14, the risk of early distress can be assessed and minimized. Many times the concrete pavement thick­ness design and jointing plan (and jointing details) can be devised to reduce the number of variants, thus minimizing the risk for early­age distresses. Regardless, the effects of stabilized subbase materials should be considered when developing the concrete panel size, and joint details such as dowel bars verses tiebars, joint arrangements and joint layout plans.

In­-Pavement Lighting Considerations

In­-pavement lighting is an important safety component of airfield pavement that must be considered when designing an airfield pavement jointing plan. Each indi­vidual light location is dependent upon: [11] the beginning, end, and spacing for a configuration of lights intended to send a certain visual message to a pilot; [12] specified offsets from pavement joints or specified lines of geometric alignment; and [13] allowable deviation based upon tolerance from a specified geometric configuration. Information on configurations and purposes for runway and taxiway lights is provided in FAA AC 150/5340­30D and it should be noted that, to achieve a proper installation of in­pavement lights, it is necessary that both light fixtures and concrete pavement be constructed within specified tolerances.

Adjusting Light Locations – There are situations when light and joint locations could conflict. Therefore the engi­neer must evaluate the position of in­pavement lighting (including individual lights) with respect to pavement joints during the design phase of a project. Typically, in­pavement lights that are within 2 ft (0.6 m) of a pavement joint necessitate the use of a boxout. (The 2 ft (0.6 m) recommendation is called the “joint offset”.) It is desirable to minimize the use of boxouts for lighting fixtures so adjustment to either the lighting or thejoint locations may be necessary, and must be determined within allowable tolerances, as explained further below (a summary of allowable lighting location tolerances is found in reference 8[14]):

  • Distance from Pavement Joints:Pavement centerline light bases typically are offset from the longitudinal pavement joint by 2 ft (0.6 m). That distance is meas­ured from the longitudinal construction or contrac­tion joint to the outside edge of the light base. Depending upon the joint spacing selected by the engineer and the required light base spacing, it is possible to adjust the beginning and end light loca­tions and avoid a compromise of the 2­ft (0.6­m) joint offset restriction at any transverse or longitudinal joint. However, it is incumbent upon the engineer to be aware of the required in­pavement light spacing when planning the longitudinal and transverse joint spacing.
  • Touchdown Zone(TDZ) Lighting: A TDZ light barrette includes 3 lights spaced 5 ft (1.5 m) on­center. To maintain the typical 2­ft (0.6­m) joint offset, the optimal panel size would be 19 ft (5 .8 m). However, this is neither a typical airfield pavement panel size nor a size compatible with the FAA and industry­recommended maximumjoint spacing found in Table 1. Therefore, the engineer must select and position the light bar to work within the constraints intro­duced by the pavement design, as well as the allow­able tolerances for positioning and offset from surrounding joints. For instance, a 3­light barrette configuration can be effectively constructed across two panels of 15 (5 m) or 12.5 ft (3.8 m) and still main­tain all tolerances. For this and any configuration, however, the engineer must also consider how the light barrette or individual lights might impact joint load transfer, as well as how to effectively isolate the light bar from the panel.
  • Lead-­off Taxiway Centerline Lights on Arcs: Lead­off taxiway centerline lights are closely spaced, and usually follow an arc path that intersects pavement joints at different angles. In most instances it is not practical to adjust the beginning and end points of the light configuration, thereby avoiding pavement joints by the desired 2­ft (0.6­m) offset. In those instances where the joint offset cannot be main­tained, the design must be examined to determine if the light base can be closer to the joint without compromising performance of the joint or the lighting fixtures. It is usually possible to find an effec­tive means of accommodating taxiway centerline lights. Unique jointing patterns might be developed to accommodate these special lights, but this is not generally recommended because of the complication they introduce for pavement construction. Changes in the slab configuration in a continuous lane of paving require an adjustment to the concrete paving machine or the use of hand placement. Changing the paving machine set­up to accommodate an irregular panel size is not cost effective.The use of hand placed concrete in areas of traffic also must be avoided when possible because the pavement will not be the same quality as when machine placed.

Mitigating an Unavoidable Conflict between Lights and Joints – Situations will arise where a light base must be closer than the 2­ft (0.6­m) desired joint offset. Under such conditions, the light must be installed using a modi­fication to the typical installation detail. However, modified installations should be avoided near contraction joints because the light assembly and/or supporting cage may interfere with the paving operation, or may be cut or damaged by a concrete saw during the joint sawing oper­ation.

The use of a boxout to resolve a joint and light location conflict should be avoided if at all possible. Using a boxout in a new runway pavement for centerline and/or touch­down zone lights should be rare because the tolerance for the starting locations of these configurations is forgiving. It is expected that there will be a conflict at pavement inter­sections because of the close light spacing, curved align­ment and changes in jointing patterns. Design engineers should closely coordinate their efforts and resolve conflicts within FAA tolerances. If the tolerance is not sufficient to resolve a conflict, a modification of the FAA standard should be considered before using a boxout.The result will benefit the owner because there is a higher probability that there will be better construction and reduction in long term maintenance and repair needs with an embedded light fixture than one placed within a boxout.

When a light base is installed closer than 2 ft (0.6 m) to a construction joint, the contractor must make provisions that it will not interfere with paving or cause a problem with joint formation or load transfer. The paving machine must be able to travel over the top of, and past the light without catching any part of the assembly. It is recom­mended that the embedded steel cage surrounding the light base be no closer than 6 in. (150 mm) to thejoint. No part of the light base, assembly or steel cage should pass through any joint line, or it could unintentionally reinforce the joint and cause uncontrolled cracking. When a light base is positioned closer than 12 in. (300 mm) to a constructionjoint, any dowel bars within 12 in. (300 mm) of the light base must also be omitted;the omission of one or two dowel bars near the light will ensure there is no unin­tended mechanical interconnection or interference. Expe­rience shows that the omission of dowels for this purpose is not detrimental to the performance of the joint.

Figure 15. Typical diamond and square boxout details for in-pavement lighting.


In­pavement Lighting Boxouts – All of the various boxout types shown in Figure 8 can be used to box out an in­pavement light. However, the most common boxouts for this purpose are a diamond or a square, two examples of which are shown in Figure 15 . A circle is the optimum shape but finding forming material in a circular shape, suffi­ciently tall and rigid for airfield construction, could be cost prohibitive.

A boxout formed using irregular geometry should not be used. Irregular geometry increases the probability that uncontrolled cracking will occur.The perimeter of a boxout should be designed as an isolation joint (Type A – Undow­eled). Thickened edge designs and/or dowels are not recommended between the boxout and the surrounding pavement. Square and diamond boxouts introduce inte­rior corners into the pavement slab; cracks may form from these corners so slabs containing square or diamond boxouts require some embedded reinforcement to hold cracks tightly together should they form.

Construction of a boxout with a thickened edge is not practical and usually not warranted. The interior boxouts for in­pavement lighting along a pavement centerline are usually located under the path for aircraft nose gear. Because an aircraft nose gear load is about 5% of an aircraft gross load, the load applied in this region of the pavement is far less than the design load for the pavement structure and additional thickness by means of a thickened edge is simply unnecessary.

Steps to Resolve Pavement Joint and Light Base Conflicts:

Step 1. Overlay the lighting plan onto the pavement joint plan.

Step 2. Adjust one or both of the plans until the lighting layout tolerances are within the allowable and the light base at each location is not closer than 2 ft(0.6 m)from the edge of the light base to the plannedjoint. If an acceptable position cannot be found to meet both lighting location tolerances and joint offsets, then consider the following:

A. The 2 ft (0.6 m) offset dimension may be infringed if the light base is adjacent to a construction joint and can be positioned no closer than 2 ft (0.6 m) to a contraction joint. The 2 ft (0.6 m) spacing from the contractionjoint is an absolute.When the contraction joint is also a longitudinal joint, an even larger spacing from the joint may be desirable and should be considered within the tolerances allowable for the light location.
B. The 2 ft (0.6 m) spacing from the light base to a construction joint may be less that 2 ft (0.6m) provided that the steel cage does not interfere with the paving operation (at least 6 in. (150 mm) from construction joint to the outside of the rebar cage). The load transfer device spacing must be adjusted along the joint and no device should be closer than 12 in. (300 mm) to the rebar cage; this option is preferred but it requires approval of a modification to standards.

Step 3. When a light base is located closer than 2 ft (0.6 m) to a pavement joint, and the edge of the light base is at least 6 ft (1.8 m) from a pavement panel corner, use a diamond boxout.Welded­wire fabric reinforcement should be placed in the upper one­third of the two panels that incorporate the boxout.

Step 4. When a light base is located closer than 2 ft (0.6 m) to a pavementjoint, and the edge of the light base is closer than 6 ft (1.8 m)to the pavement panel corner, use a square boxout. The minimum dimension of encroachment into any panel is 2 ft (0.6 m). To be consistent with the aspect ratio limit, the longest side of the boxout is not to exceed 1.25 times the length of the shortest side. Welded­wire fabric reinforcement should be placed in the upper one­third of each of the panels surrounding the boxout. Load transfer devices may also be considered if the boxout is located where it would be subject to frequent loading by the main gear of departing aircraft.

Coordination in Design Plans – It is currently common practice for construction documents to be supplied to the contractor without the pavement jointing plan and lighting plan being coordinated by the engineer.This prac­tice is based upon the assumption that the contractor, and the respective sub­contractors, can resolve conflicts between pavement joints and light base locations in the field.

It is the responsibility of the engineer to coordinate the pavement jointing and lighting layout plans. The engineer must resolve conflicts before the construction documents are made available to the contractor. Coordinating light locations with paving plans during design reduces the probability that significant field changes will be required during construction and saves project time and expense.

More details on these and other best­practices for constructing in­pavement lighting for airfield pavements are available in reference 7.[15]

References

  1. Airport Pavement Design and Evaluation, FAA Advisory Circular AC 150/5320-6E, Federal Aviation Administration, Washington, D.C., 2008.
  2. Design of Concrete Airport Pavement, American Concrete Pavement Association, EB050P, Skokie, IL, 1986.
  3. Design and Control of Concrete Mixtures, 14th Edition, Portland Cement Association, EB001.14, Skokie, IL, 2002.
  4. Burns, C.D., and others, “Multiple-Wheel Heavy Gear Load Pavement Tests, “ Volume II, Technical Report S- 71-17, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 1971.
  5. Airport Pavement Design and Evaluation, FAA Advisory Circular AC 150/5320-6E, Federal Aviation Administration, Washington, D.C., 2008.
  6. Pavement Design for Airfields, “Plain Concrete Pavements,” Chapter 12, Unified Facilities Criteria, UFC 3- 260-02, Joint Departments of the Army Corps of Engineers, Naval Facilities Engineering Command, and Air Force Civil Engineer Support Agency, Washington, D.C., June, 2001.
  7. Design of Concrete Airport Pavement, American Concrete Pavement Association, EB050P, Skokie, IL, 1986.
  8. Hall, J.W., and others, “Stabilized and Drainable Base for Rigid Pavement - A Design and Construction Guide,” Report IPRF-01-G-002-021(G), Innovative Pavement Research Foundation, October, 2005 .
  9. Hall, J.W., and others, “Stabilized and Drainable Base for Rigid Pavement - A Design and Construction Guide,” Report IPRF-01-G-002-021(G), Innovative Pavement Research Foundation, October, 2005 .
  10. Hall, J.W., and others, “Stabilized and Drainable Base for Rigid Pavement - A Design and Construction Guide,” Report IPRF-01-G-002-021(G), Innovative Pavement Research Foundation, October, 2005 .
  11. Airport Pavement Design and Evaluation, FAA Advisory Circular AC 150/5320-6E, Federal Aviation Administration, Washington, D.C., 2008.
  12. Design of Concrete Airport Pavement, American Concrete Pavement Association, EB050P, Skokie, IL, 1986.
  13. Burns, C.D., and others, “Multiple-Wheel Heavy Gear Load Pavement Tests, “ Volume II, Technical Report S- 71-17, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS, 1971.
  14. Design and Installation Details for Airport Visual Aids, FAA Advisory Circular AC 150/5340-30D, Federal Aviation Administration, Washington, D.C., 2008.
  15. Sonsteby, O.A., “Constructing In-Pavement Lighting, Portland Cement Concrete Pavement,” Report IPRF 01-G-002-03-1, Innovative Pavement Research Foundation, March, 2008.