9

2 TECHNICAL SYNTHESIS

2.1 Innovative Concrete PavementTechnology in Europe

The US TECH Study Tour observedmany interesting and innovative ideas,technologies, procedures, equipmentand processes related to concretepavements that will be of interest toengineers and administrators in theUSA. Many of these have beenresearched in the USA before but havenot been widely implemented.

Pavement Design

A summary of typical designs forfreeway type highways is shown inTable 2.1. Several countries are alsobuilding unbonded CRCP or JPCPoverlays over existing concretepavements. A summary of Europeanpractices for concrete pavements isreproduced in the Appendix.

Table 2.1 Summary of concrete pavement designs for countries visited.

France

C R C P17-25 cm

(6.7-10 in)

JPCP22-28 cm(8.7-11 in)

- - -

45.5 m(13.1-18 ft)

LCB n/a

LCB n/a

Austria

Germany

JPCP18-25 cm(7-10 in)

JPCP20-30 cm

(7.9-11.8 in)

5.5-6 m(18-19.7 ft)

(9.Z)

5 cm (2 in) ACCTB

CTB/LCB(bonded)

Min. bearingcapacityrequired

Granularblanket

30-90 cm(11.8-35.4 in)

NetherlandsJPCP

26-28 cm(10.2-11 in)

3.5 - 5 m(11.5-16.4 ft)

LCB Sandlayer

Belgium

C R C P

(?!9,

JPCP23 cm(9 in)

- - -

5-6m(16.419.7 ft)

LCB

LCB

20 cm (7.9 in)minimumgranular

20 cm (7.9 in)minimumgranular

1, All joints dowelled, 26 mm (1 in) diameter typicalLCB = lean concrete base, AC = asphalt concrete, C T B = cement-treated base

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’ . Catalog of Designs

Most countries have developed acatalog of pavement designs-for asphaltand concrete pavements. Thesedesigns appear to be based upon boththeoretical analyses and practicalexperience from a team of experts.They are based on data unique to agiven country or region. A designcatalog is helpful in communicating theappropriate design to administratorsand to the field.

Especially for concrete pavement,having the details of the cross sectionclearly defined may help avoidconstruction problems. In addition,project designers do not need tounderstand all of the theory involvedto design a pavement when using acatalog. Germany has a catalog forboth new pavement design andanother catalog for rehabilitationdesign, part of which is shown inFigure 21.

JPCP overlay on interlayer of lean concrete or AC on fractured old pavement.

MflC

ClassJPCP overlay

Interlayer

slab i” ia iz izFractured old

Subbase

JPCP overlay on geotextile on fractured old pavement.

Traffic S V I I I IIIClass

JPCP overlayGeotextile 27 2 3 23

Fractured oldslab

Subbase

JPCP full-depth reconstruction with untreated, open-graded permeable base.

Traffic 1 sv 1 I II 1 IIIClass I

Open-gradedpermeable

b a s e

* Moduli in MPa (1 MPa = 145 psi), thicknesses in cm (1 cm = 0.3937 in)

Figure 2.1 Portion of the German design catalog for rehabilitation alternatives.(Note that many other factors are specified such as minimumfoundation bearing capacity, concrete strength, drainage, joint design,etc. See cross-sections shown in Figures 2.4 and 2.10).

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l Thick Granular Layer OverSubgrade (Beneath LCB or CTB)

Nearly all countries provide a thickgranular layer (20 to 90 cm (8 to 35 in))between the subgrade and the treatedbase course to control frost heave andincrease support to a minimumspecified bearing design level. Note inFigure 2.1 the minimum modulus ofelasticity that must be met at the top ofthe subgrade (45 MPa (6,500 psi)) andat the top of the granular layer (120MPa (17,400 psi)). This plate load test(German standard test DIN 18134, June1990) involves a circular plate loadedin several stages. In each load stagethere is a wait until the change insettlement does not exceed a specifiedvalue. The minimum modulus ofelasticity required results in a relativelystiff foundation upon which the treatedbase course (i.e., lean concrete) andconcrete slab are supported.

l Long Design Lives

Many of the countries structurallydesign concrete pavement for longdesign lives of 30 to 40 years. Thislong design life may be in partresponsible for the excellentperformance of concrete pavements inEurope.

l Heavy Truck Traffic

This situation currently exists inEurope and the expectations in everycountry visited are that traffic willcontinue to increase in volume andweight even more rapidly with theeconomic growth that the EC willbring. Some countries will be

increasing their legal axle weights tomatch the EC standard of 11.5 t singleaxle (25,300 pounds), while othersexceed this already. A summary oflegal axle loads which shows the largedifferences from the USA load limits isprovided in Section 1. Most trucks inEurope observed by the Study Tourhad super-single tires.

France provides one example ofgrowth in heavy truck traffic. Francehas had large increases in its volume oftrucks and expects an 8 percent annualgrowth in trucks. Truck volumes onthe outer lane of urban freeways rangefrom about 2,000 to 10,500 per day.Legal axle loads are among the highestin the world: 13 t (28,600 pounds) forsingle axles and 21 t (46,300 pounds)for tandem axles.

l Life-Cycle Cost Analysis

Some countries such as France conductlife-cycle cost analyses of pavementalternatives over a 25 to 40-yeardesign period using a discount rate, nouser costs and a new surfacing atspecified times. Other countriesinclude only the construction cost inthe economic analysis. The Frenchphilosophy is expressed by thefollowing remarks:

“The pavement structures given in thecatalogue of standard designs areequivalent and offer the same servicelife. However, the amount ofmaintenance needed to preventpremature aging of the structures andto guarantee satisfactory surfacecharacteristics differs. One of the

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advantages of concrete pavements isthat they require very littlemaintenance. This is why an economiccomparison of pavement structuresmust also look at the global investmentcost including maintenance.”

l Full-Width Paving for FutureTraffic Control

Several countries such as Germany, theNetherlands, and Austria build theirstandard two-lane, one-directionfreeways with the full-depth concreteslab wide enough (11 m (36 ft), 11 m(36 ft), and 11.5 m (38 ft) in those threecountries respectively) to be capable ofhandling four lanes of traffic for anyfuture emergency (such as a landslide)

or planned rehabilitation. This makesit possible to completely close theopposite direction for rehabilitation.Shoulders are called “emergency lanes”in Europe for this reason.

l Widened Truck Lanes

This has been a widely used concretepavement design in most Europeancountries for many years to reduceedge and corner loadings. The StudyTour observed many pavements with awidened truck lane during the trip.The edge stripe is placed at its normallane width position. Some countriesalso include tied concrete shoulders, asshown in Figure 2.2.

Figure 2.2 Typical widened traffic lane (4.25 m (13.9 ft)) with paint stripe placed0.5 m (1.6 ft) from edge of pavement.

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l Trapezoidal Cross-Section

This interesting design concept hasbeen used in several countries, mostnotably France and Spain. Thepurpose of this design is to provide thethickest slab in the most critical area ofloading (the outer edge of thepavement) while minimizing theamount of concrete used. The Frenchuse a trapezoidal cross-section on newpavements as well as reconstructedlanes. In the French trapezoidal cross-section, as shown in Figure 2.3, the slabthickness varies from 26 to 29 cm (10to 11.5 in) across a 7-m slab (23-ft) (twol a n e s ) .

l 3-D Finite Element Use in Design.

The French developed and use a three-dimensional finite element analysisprogram called CESAR to assist themin developing their concrete pavementdesigns.

l Unique German ConcretePavement Design

This pavement design impressed theStudy Tour by its proven history ofexcellent performance and forconceptual reasons. It is shown inFigure 24 and has several uniquecharacteristics listed.

(1964 original) (1976 reconstruction)

Figure 2.3 Example French trapezoidal cross-section designfor reconstructed traffic lanes.

l Unique JPCP and CRCP PavementDesign from Belgium and Austria

Placement of an AC layer between aPCC slab and a base (lean concrete,cement treated, or untreated granular)

is required in some countries, includingBelgium and Austria. The AC layerprovides a bond between the slab andthe base and reduces erosion. Somesections in Belgium where the AC layerwas eliminated have resulted inerosion and punchouts in CRCP.

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motor way

22cm to 26cm

L treated base course L-porous concrete

blanket (a) 10 cm (4 in) bitumen treated basegranular layer (b) 15 cm (6 in) cement treated base

or lean-concrete base

. Jointed plain concrete pavement.l Slab thickness depends on traffic.. Usually two-layer construction with slab containing highquality crushed aggregates.. Widened traffic (both passing and truck) lanes.. Full-width paving thickness for future traffic control during rehabilitation.. Shoulder is tied concrete.. Concrete strength is similar to USA.. Base is cement treated or lean concrete.. Base is bonded to slab, reflection cracking is avoided by providing joints (or notches) in the base just

beneath joints in slab.

.

Subbase consists of a thick granular blanket.Transverse joint spacing is relatively short.Doweled joints, unevenly spaced, plastic-coated dowels, automatic dowel placement.Transverse and longitudinal joint sealant is neoprene compression seal.Longitudinal joint saw depth is 0.40 - 0.45 of slab thickness.Subdrainage with a porous concrete layer beneath the outer shoulder plus circular pipes connected to aclosed drainage system. The underlying granular blanket provides some bottom drainage.Surface texture currently used is a light longitudinal brush (burlap drag) to produce a low-noise surface.The hard highquality aggregates used in the top layer provide adequate friction. The uniform cross-slope required is 2.5 percent.

Figure 2.4 German jointed plain concrete pavement design.

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This is accomplished by notching thebase immediately after placementexactly beneath the transverse andlongitudinal joints of the concrete slab.The bond lasts at least 10 years andprovides a monolithic slab whichreduces curling stresses and erosion atthe interface, which often occurs whenthe layers are debonded (SeeFigure 25).

l No Crown, Straight Cross-Section

Most countries have a straight 2.5percent cross-slope across all trafficlanes and shoulders to promote rapiddrainage and smoother pavements.

l Notched and Bonded LeanConcrete or Cement-Treated Base

Germany bonds a lean concrete base orCTB to the slab with good successwithout the risk of reflection cracks.

Figure 2.5 German JPCP slab on lean concrete base that has been notched or jointed.(Note: all joints along project showed an initial crack like this joint aftera few days curing.)

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l Longitudinal Edge DrainsConnected to Closed DrainageSystem

The German cross-section (Figure 2.4)shows a porous concrete layer beneaththe shoulder that provides a flowchannel to a longitudinal subdrain.This empties at regular intervals into alateral pipe and finally into a largerlongitudinal closed drainage system.

l Ditch Line One Meter (Three Feet)from Bottom of Base

The Netherlands requires this to helpdrain the cross-section. Pavements inother countries also appeared to havedeep ditch lines.

l Geotextile Drainage FabricBetween Slab and Base

This is specified in Germany to beplaced between a new JPCP overlayand old fractured concrete slab. InFrance, the Study Tour observed athick fabric placed beneath the slab ontop of a granular base.

l Porous Concrete Base UnderShoulder

A porous concrete base about 15 cm(6 in) thick is specified in Germany’scross-section under the outer concreteshoulder to facilitate base drainage, asshown in Figure 2.4. This is also usedin France and Italy to drain the cross-section. The porous layer is connectedinto a drainage system in all cases.

l Reinforcement in CRCP

Some unique and interestingreinforcement designs were found inEurope:

J Rectangular flat steel high-strengthstrips (FLEXARM): A coilablereinforcement was developed in France(Figure 2.6) to shorten the length of theconstruction train, reduce thecomplexity of bar reinforcementplacement, reduce the labor involvedand make the reinforcement easier totransport. This reinforcement has beenused in France since 1988 for severalmajor freeway projects under thecommercial name of FLEXARM. Thiscarbon steel has a high yield strengthof 790 MPa (114,550 psi), a flatrectangular section (4 cm (1.6 in) wideand 2 mm (0.08 in) thick), a corrugatedsurface which is corrosion-proofed bycontinuous hot galvanization, issupplied in coils and is joined in thefield by rapid pneumatic riveting.

J Using an increased steel percentagehas shown excellent performance inEurope: Belgium used 0.85 percentfrom 1970 to 1978 and obtainedexcellent long-term performance onover 100 km (62 miles) of heavilytrafficked freeway with no punchouts.Projects in France and Spain with 0.72to 0.85 percent steel have shownexcellent performance also.

J Placing the steel above mid-depth:A depth of approximately one third ofthe slab thickness holds cracks tighterand results in better performanceaccording to experienced engineersfrom Belgium and France.

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Figure 2.6 Coilable rectangular reinforcement (FLEXARM) developed in France.(Note: coils held in diagonal position at top of photo.)

,/ Skewed transverse steel: Used inBelgium to prevent any transversecracks from forming over transversesteel.

l CRCP with Porous Asphalt andConcrete Surfacings

CRCP is surfaced in the Netherlands,France and Italy with porous asphalt.Porous concrete has also been used inNetherlands and France. This designhas some strong advantages anddisadvantages, as described in thesection on surfacings.

l Dowels Required to ControlFaulting

Based upon experience in manycountries, the overall conclusion is thatdowels are required to control faultingin transverse joints for JPCP for heavilytrafficked highways in Europe. Thiswas strongly stated, based upon fieldexperience, in Belgium, Germany,Netherlands, Austria and Spain. Thisconclusion was painfully learned inseveral countries that adopted thetypical original “California” design forJPCP with no dowels, an erodible baseand no subdrainage. This led topumping, faulting, and slab cracking.

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l Varying Dowel Placement AcrossTraffic Lanes

Nearly all countries vary the dowelplacement across the traffic lanes andemergency lanes (shoulders) toeconomically place adequate loadtransfer devices at the locations wherethe greatest number of heavy wheelloads pass. Automatic dowelplacement equipment can placenonuniform dowel patterns. Anillustration of dowel spacing inGermany is given in Figure 2.7.

l Plastic-Coated Dowels andDeformed Tie Bars

Germany uses 25-mm-diameter (1 in)dowels with a plastic coating at least0.3 mm (0.01 in) thick covering thetotal length of dowels and no oil used

at construction. They are placed withautomatic dowel inserters. Theapparent quality of the coating wasimpressive.

l Short Transverse Joint Spacing

Joint spacing in JPCP is critical tominimize transverse cracks due tocurling and warping. Europeancountries have clearly recognized thisfor many years and joint spacing inmost of these countries ranges from 4.5to 6 m (15 to 20 ft), with 5 m (16.5 ft)being the most popular. Since mostjoints are doweled, the transverse jointsare perpendicular to the centerline.Slab thicknesses range from 22 to 28cm (9 to 10 in) for these joint spacings.A 5-m (16.5ft) joint spacing was alsoused at the new Munich II airport forslab thicknesses up to 40 an (16 in).

8.5 m0 (28 ft)0.5 (1.7 ft)

10.5 (1.7 ft)

3.75 m0 (12.3 ft) 3.75 m (12.3 ft) I \ 2.50 m., (8.2 ft)

inner lane outer lane shoulder

concrete

27dowels :25mm (1 in) 1 II I I IIIII~IIIII Illlll~lI Illi

7X5Oan (2Oin) 1 : 14x25anl3x4oan15x25anl ’1 ’ 1 (loin) 1 (2Oil-l) 1 (loin) 1 ’

1 4X5ocm 1 ’

25 25’1 (2Oin) 1 1

25 25(10 in) (10) 00) (10) (10)

Figure 2.7 Varying dowel bar spacing across pavement in Germany.(See Figure 2.4.)

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l Sealing of Joints

European countries differ as to whetheror not they seal joints and as to whattype of seal they use. Most countriesseal transverse and longitudinal joints.An exception to this is Austria, wherein some areas a narrow (3 mm (0.1 in)wide) joint is saw cut and not sealed,which reduces construction cost byabout 10 percent. Spain sealstransverse joints in wet areas but not indry areas. Longitudinal joints aresealed in all areas in Spain.

l Two-Layer Construction Concept

This concept is used in severalcountries in Europe for economic andsafety reasons. Equipment is availableto slipform two layers in one pass asdescribed below.

J Two-layer construction has beenused extensively in Germany sincethe 1930’s on highway and airportpavements. This provides aneconomical design, with the top layercontaining hard, high-quality, smaller-sized, high-friction aggregates and thelower layer containing lower-cost,locally available gravel aggregates(which must be thermally stable). Thetop surface is more resistant to freeze-thaw damage, has a lower noise leveldue to the smaller aggregates, and hasimproved friction.

J Two-layer construction is usedcurrently in Austria to provide a toplayer with hard and durable smaller-sized aggregate (8 mm (0.3 in)maximum). An exposed aggregatesurface is then created to provide a

low-noise, high-friction surface. High-quality aggregates are expensive andcannot be used throughout the full slabthickness. Figure 2.8 shows a photo ofa two-layer slab from Austria.

J Two-layer construction is used inFrance with hard aggregates in thesurface layer to provide an exposedaggregate surface. These aggregatesare very expensive compared to softlimestones used for the lower layer.

l Pavement Placed Right OverBridges

Some countries such as Belgium andFrance design some bridges for theextra dead load of the pavement whichis placed right over the bridge deckThis avoids end movement problems.

l Concrete Pavement Bicycle Pathsand Local Traffic

The Netherlands constructs manyundowelled JPCP bike paths. Theseare also used by local farm equipment.

l Prestressed Concrete Pavements

This pavement type has beenconstructed by several countries inEurope, mostly at airports. Prestressedpavements have been used extensivelyat Schiphol Airport (Amsterdam) for 25years and have provided low-maintenance long lives under heavytraffic. The first prestressed pavementin the world was built in Portugal at aNATO airfield in 1965.

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Figure 2.8 Two-layer construction in Austria (high-quality smaller-sized aggregatesin top layer, lower-cost locally available aggregates in lower layer).

l Concrete Block Pavers Construction

This has been used to some extent inmost European countries for localstreets and other purposes. Forexample, they are used extensively inthe Netherlands for a wide range ofapplications from domestic pavementsto complicated industrial pavements.

l Reduced Electrical Energy

In Switzerland, lighting concretepavements consumes about 20 percentless electrical energy than lightingasphalt pavements due to the lighter-colored surface.

Some interesting contractingarrangements are going on in highwaydesign and construction in Europe. Forexample, Germany paid eight firms150,000 DM each to develop proposalson a 30-km (l8.6-mi) highwayreconstruction project. The low bidwas 105 million DM, which was lowenough to cover all of the money spentto develop the innovative proposals.

. Warranties for Construction

Most highway work in Europe requireswarranties for highway constructionand materials.

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A few examples: Germany has afour-year warranty for concrete andasphalt pavements, and Frenchcontractors must warrant AC pavementfor four to five years and concretepavement for seven to nine years. TheFreyssinet load transfer devices carry afive-year warranty.

While some sources claim thatwarranties contribute to the highquality of pavements in Europe, moreevidence is needed to support thisconclusion. Beyond qualitativeevidence, cultural differences betweencontractor and owner on the twocontinents must be investigated. Theinterrelationships of workmanship,ability to pay, construction or designchoices allowed, size of company, etc.,lead us to believe that the word“warranty” may mean different thingsto Europeans than to Americans.

A primary reason for the achievementof quality highways in Europe is alonger original design life and aEuropean mindset for-long term use ofnot only highways but also homes, carsand all other products. Europe is not adisposable-driven economy. Designsinclude a large safety factor. Forexample, concrete actual strengthsregularly exceed by a considerableamount design strengths, and designstrengths were considerably higherthan ours. USA construction contractsand quality control programs arefocused on uniformity and building asclose as possible to specifiedrequirements, whereas their designsand contracts are focused on gettingthe best, longest-life product possible.The European designs and

specifications achieve and exceeddesired results with minimum risk

l Two-layer Paving Equipment

This construction procedure isextensively used in Germany, Franceand Austria. For example, equipmentused at the new Munich II Airportpaved, in one pass, a 14-cm (5.5in)granite aggregate top course and a22cm (9 in) lower course made of localround gravel, forming an economical36-cm (14-in) monolithic structure.Dowel and tie bars were placedbetween these layers. A “doubledecker” slipform paver is available thatcan place two separate layers “wet onwet” to form a monolithic structure.The two layers are completely differentconcrete mixtures.

l Workability Meter

This is used in France to controlworkability of concrete. It consists of abox with a swinging door that opensup and lets concrete flow outdepending on its flowability.

. Lower Productivity Rates andHigher Costs

Typical construction costs in Europeappear to be about double those of theUSA. Of this higher cost, about 50percent appears attributable to higherstructural design standards and thebalance to lower productivity fromboth an equipment and laborstandpoint.

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l Short Construction Duration

Several examples of relatively fast-trackconstruction exist in Europe, A 17-km(10.6mi) project (11.25-m (37-ft width),which included crushing and recyclingthe concrete pavement, was completedin 26 weeks in Austria. The Base1airport runway was reconstructed withonly one week of actual closure andtwo weeks of replacing concrete slabsat night and opening at 5 AM. Earlyopenings of slab replacements within24 hours were reported in Vienna.

l Uncrowned Pavement Cross-Slope Improves Ride

Nearly all European countries areusing an uncrowned straight cross-slope. This is believed to provideimproved rideability.

l Liquidated Damages = IncentivesRate / Day

A project on the Al freeway in Austriahas a specified maximum constructionperiod with provisions that the damagerate per day is equal to the bonus rateper day. The contractor felt that thiswas fair and provided considerableincentive.

l Re-bar Tubes Behind Vibratorsfor CRCP

This procedure illustrated in Figure 2.9provided an accurate final position ofthe reinforcement for a French project.They believe they are able to meet aspecification of + 1.5 cm (0.6 in) byputting the tube at the end of theliquid phase of the concrete.

vibrator-

reinforcement ba

Figure 2.9 Position of tubes and vibrators used in France to place CRCP to improveposition of reinforcement.

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l Prevention of Sawing Residue fromEntering Joint

Germany and the Netherlands use along elastic band to plug the first deepsaw cut to keep residue from thesecond joint sealant reservoir cuttingfrom infiltrating the crack This isconsidered important to keepincompressibles out of the joint prior tos e a l i n g .

l Lean Concrete TemporaryWidening for Traffic Control

This was used on the A10 autobahnnear Berlin to widen old concretepavement to carry 4 lanes of trafficover an S-month period. The 22-cm (9-in) lean concrete will be recycled alongwith the old concrete after the otherside of the highway is reconstructed.

l Concrete Mixing

Maintenance and Rehabilitation

l Extensive Recycling of PCC andOther Materials

Recycling of concrete is performed allover Europe. Belgium recycles PCCinto LCB. Germany recycles concreteinto LCB and the granular blanket.Netherlands includes recycled rubblein LCB. Austria recycles old PCC intonew PCC and believes that crushedconcrete provides coarse aggregate ofvery good quality. To achieve lowcost, Austria permits some existing ACoverlay to be used in the recycledconcrete. France has conducted severalsuccessful recycling projects since 1976using crushed concrete in new concreteand in the lean concrete base.

l Unbonded CRCP and JPCPOverlays (Some on FracturedJPCP)

The concrete plants observed werecompulsory mixing plants, and inFrance, continuous mixing plants. Notilting drum mixers were seen, which isvirtually the only kind of mixer used inthe USA. Drum mixers are commonbut discharge by pulling apart ratherthan tilting. Europeans felt that theircentral mix plants produced higher-quality concrete. Further investigationis needed to find out whether or notthis belief is justified.

l Vibration

Two slipform pavers observed wereequipped with “T”-shaped vibrators.The USA needs to investigate this typeof vibrator to determine its merits.

CRCP and jointed fiber-reinforcedunbonded overlays of concrete andasphalt pavements are used often inBelgium with good success. InGermany, the existing concretepavement is fractured into pieces and a10-cm (4in) interlayer of either notchedlean concrete or AC material is placedon top of the existing concretepavement. A JPCP overlay is thenplaced with the same thickness as isused for new design. Another Germanoption is to place a 6-mm-thick (0.2 in)geotextile between the fractured oldconcrete pavement and a slightlythicker JPCP overlay.

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Austria has placed a JPCP unbondedoverlay over a thin AC separation layeron top of fractured slab. France hasplaced a lot of CRCP overlays over oldfractured JPCP. Typical designincludes the following features: l&cm(7-in) CRCP with 0.67 percent steel andl&cm (7-in) lean plain concreteshoulders with transverse joints at 6 m(20 ft) placed on the fractured JPCP. Alongitudinal drain is placed along theedge. The transverse cracks in theCRCP were tight and the pavementwas in excellent condition. This CRCPoverlay is typical of several observed.

Spain has used roller-compactedconcrete (RCC) for overlays of

4.25 m

I (14 ft)

22 cm (9 in)

15 cm (6 in)

pavements. An AC overlay is placedon top of the RCC to provide goodrideability. Spain favors RCC foroverlays because it can be opened totraffic very quickly.

l German Lane Reconstruction

The existing deteriorated traffic lane iscompletely removed and a new JPCP isconstructed over a porous concretebase layer about 40 cm (16 in) thickThe new 26-cm (10.5-in) JPCP is placeddirectly on the porous concrete layer.The new lane is tied securely to the oldtraffic lane with deformed reinforcingbars. This cross-section is shown inFigure 2.10.

4.25 m 2 5 m

1 (14 ft) , (8 ft) ,

Q”ganular blanket layer ---- ,

4---(4% 22.5% __)

Figure 2.10 German cross-section for lane reconstruction with porous concrete base.

.

In

German Total WidthReconstruction

general, it appeared that Europeanstended to reconstruct or resurfacerather than restore concrete pavement.All of the existing pavement isremoved and a JPCP is placed on anuntreated permeable base course. Thisbase type is new for Germany;however, this technique makes itpossible to use up to 100 percentrecycled material from the oldpavement. Slab thickness is increasedfor this option over that used for thenormal lean concrete base.

l French Lane Reconstruction

Trapezoidal cross-sections have beenused on many freeway reconstructionsof one or two lanes. Typical thicknessis 26 cm (10.5 in) at the inside edge to29 cm (11.5 in) at the outside edgeacross two lanes, a 0.75-m (2.5 ft)widened traffic lane, a lean concrete

25

base, and a cement-stabilized soil, asshown in Figure 2.3. Longitudinalsubdrainage along the edge is used.This design carried more than threetimes the truck loadings than theoriginal traffic lane having theconventional “California” design.

l CRCP Widening on AC Pavementfor Added Truck Lane

Several major projects in France havebeen completed where either the outerAC traffic lane was removed andreplaced with CRCP or a lane wasadded by removal of the shoulder andreplacement with CRCP. A largeproportion of trucks use this outer laneand due to the previous majordeterioration in this traffic lane it isbelieved that the future will require avery heavy structural design. Oneproject observed by the Study Tourhad a 31.5cm (12.5in) CRCP slab, asshown in Figure 2.11.

Figure 2.11 CRCP truck lane addition to original AC pavement in France.

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l Automatic Faulting Measurements

Faulting measurements taken directlyfrom the APL profile were shown tothe Study Tour. The extent oftransverse joint faulting was readilyobservable and measurable.

l LCPC/Freyssinet Load TransferDevices

The French LCPC laboratories andFreyssinet International havedeveloped a device to restore high loadtransfer in the transverse joints of

undowelled JPCP. These undowelledjoints exhibit poor load transfer thatleads to faulting and slab cracking ofthe original slab, plus deterioration ofreflection cracks of an AC overlay.These devices have been placed onmany sections of JPCP in France withgood success in restoring load transferfrom less than 50 percent to over 90percent. They have been successfullyused prior to placement of a porousasphalt surface to reduce reflectioncracking. A Freyssinet load transferjoint or crack is shown in Figure 2.12.The device carries a warranty.

Figure 2.12 LCPC/Freyssinet French load transfer device.

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l Rehabilitation Programmed whenPavement Condition is “Good”

It appeared to the Study Tour that farless pavement deterioration is allowedin European pavements beforerehabilitation is done than in the USA.This was especially true for toll roads.The Study Tour was very impressedwith the extent to which the toll roadcompanies are vitally concerned withproviding the highest-quality service tousers and are constantly seeking toimprove service levels.

l Fiberlzed PCC Overlay ofAC Pavement

Used successfully in Belgium forseveral projects. One project observedby the Study Tour had a 12-cm (5-in)steel fiber-reinforced concrete overlayplaced over a badly rutted ACpavement. A 10-m (33-ft) undowelledjoint spacing was used; however, curlis considerable. The existing 22-cm(9-in) AC pavement was milled 12 cm(5 in) prior to placement of the 12-cm(5-in) fiberized concrete overlay. Thepavement was in excellent conditionafter four years. A 5-m (16.5ft) jointspacing has been built and workedwell. Belgium has constructed over130,000 square meters (142,200 squareyards) of this type of overlay onconcrete and asphalt pavements.

l JPCP Overlays of AC Pavements

Several have been built in Francestarting in the 1970’s. They haveshown very good performance overmany years. Their typical slabthickness was 21 to 25 cm (8.5 to 10 in),4.5-m (14ft) undowelled joint spacingwith 600 to 1000 trucks per day in one

lane. The new JPCP overlay is placeddirectly onto the old pavement, or ontoa leveling course of lean concrete.

l Performance of Overbanding ofLongitudinal Lane/Shoulder JointSeal Performance

The French used polymerized SBSasphalt hot-poured joint sealant in anoverbanding configuration between theconcrete traffic lane-and the ACshoulder. This sealant was observed tohave performed very well in the 6years since construction.

l Thin Polymerized AC Layer forStudded Tire Wear in Austria

Studded tires caused considerabledamage to older Austrian pavements,resulting in ruts of 2 to 3 cm (0.9 to 1.2in). Since Austria has a lot of rain,some type of rehabilitation had to beperformed. A thin polymerizedasphalt layer has been placed over thetruck lanes of many older concretepavements to fill in the studded tiredamage. This layer has a life of onlyfour to six years.

l French Pavement Evaluation

French research has developed severaltypes of pavement monitoringequipment. The latest equipmentdevelopment is called the SIRANOwhich measures profile, takescontinuous 35-mm film for a lanewidth and determines macro-texture ata speed of 72 km/hr (45 mi/hr). TheSIRANO successfully tested 5,500 km(3,415 mi) in 1991.

The French also conduct acomprehensive evaluation to determine

the need for and design of pavementrehabilitation. A policy of preventionis encouraged, in which a rehabilitationaction is taken as soon as fatiguecracking has initiated (i.e., before moreserious structural deterioration of theslab and base occurs).

Concrete Materials

l Highly Durable Concrete Slabs

The Study Tour traveled extensively onthe European freeway system and didnot observe any concrete durabilityproblems. Discussions with engineersin each country revealed that very fewdurability problems exist. Someexamples that provide some possiblereasons for this are provided.

J 1930’s German autobahns show nodurability problems after more than50 years. This old concrete had thefollowing characteristics: lower trafficduring its early life, a relatively mildclimate, care in proportioning uniformgradation mixes, 3-cm (1.2 in)maximum size, high-quality, hardaggregate in the top course,consolidation by vibration, a dryconcrete mix (water-cement ratio lessthan 0.35), 21-day water curing,protection of concrete from sun andwind with 21-day tent cover, nodeicing salts used for many years, anda thick granular layer between the slaband the subgrade (except in areaswhere a sand subgrade was present)that provided some bottom drainage.A photo of a 1939 concrete pavementon the German autobahn is shown inFigure 213.

Figure 213 Photo of original 1939 concrete pavement on the German autobahnapproaching Berlin from Munich.

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J Germany has a quality testingprogram to achieve durableaggregates, correct gradation ofaggregates, and a good air voidsystem. The air void system isdetermined during construction usingthe Danish meter for fresh concrete todetermine the air void content andvoid system. Tests are conducted thefirst day of production and again ifthere is any doubt as to air voidsystem. The tent cover for a two-hourminimum (7 days at the Munich IIAirport project) provides surfaceprotection for early curing.

J Swiss quality control program forconcrete durability. The measurementof the total content of air voids of thefresh concrete was not sufficient for theevaluation of frost and chloridedurability in Switzerland. Only anappropriate testing method applied tothe hardened concrete can givepertinent information. Rapid andpractical procedures were developed toexamine the hardened concrete. Themicroscopic control of concrete iscarried out on thin sections made froma concrete core specimen impregnatedwith a special fluorescent dye andexamined under the microscope intransmitted ultraviolet light.

Laboratory tests are conducted a fewmonths before the project begins.Aggregates are submitted to qualitytests. Several concrete mixes areprepared at the laboratory to work outa mix design of high durability with agood air void system (size, quantityand distribution in the cement pasteare measured).

Trial run tests take place two to threeweeks before construction to evaluatethe batching, mixing plant, andplacement equipment to test thesuitability of the mix design from thelaboratory under in situ conditions.The concrete is mixed, hauled andplaced in two or three trial slabs.Several test cores are obtained andtested, and the results are compared tothose obtained in the laboratory. Anyneeded adjustments to the mix orconstruction process are made.

During the first few days ofconstruction, cores are taken from thepavement and tested. A microscopicanalysis is again conducted to ensurethat the hardened concrete maintainsthe proper air void system. Theseresults are -available within 36 hoursafter the concrete is placed. If the airvoid system is inadequate, a rapid-cycle freeze-thaw test is conducted onone of the cores (Dobrolubov-Romer).If the air void system is inadequate, thesurface of the concrete is impregnatedwith an agent. These quality controlprocedures have led to the eliminationof frost-salt durability problems inconcrete pavements in Switzerland.

Not many concrete pavement projectsare constructed; however, when theyare a comprehensive preparation isaccomplished. This amount ofpreparation would increase our costsgreatly in the USA.

J Austria has very durable concretewith no significant problems even ina harsh climate. Pavements built inearly 1950’s showed no durabilityproblems.

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J France requires the proportioningof aggregate to achieve minimum voidcontent.

l Blended Cement and ConcreteMixtures in Spain

Spain uses concrete containing crushedlimestone as the coarse aggregate,which has proven to yield lowshrinkage and good flexural strengthand facilitates joint sawing. Therequirement that at least 30 percent ofthe fine aggregate be composed ofsiliceous particles has resulted inpavements without friction problemsassociated with texture wear. Concretemust attain a flexural strength at 28days of 4.5 MPa (640 psi) from athird-point loading test. Blendedcement containing flyash (blendingmust be done at the plant) is used inthe concrete (38 percent flyash) andlean concrete base (50 percent flyash).A large cost reduction was obtained bythe government for these blendedcements for use in pavements! Thewater/cement ratio is between 0.44 and0.50, slump is between 2 and 4 an (0.8and 1.6 in), and plasticizers are used indrier mixes.

l Steel-fiber Reinforced PCC

Belgium has built 12 or more projectsas previously described. They include5-cm-long (2 in steel fibers (30 kg/m3(50 pounds/ yd4 ) steel) and performedwell: no cracks were observed in thelong slabs (10 m (33 ft) joint spacing).Shorter slabs are recommended.

l Higher-strength Concrete in Slabs

Some countries, particularly Belgium,use much higher-strength concrete thanthe USA. Belgium uses a high cementcontent (400 kg/m3 (674 pounds/yd3))which produces a strong, denseconcrete having a minimumcompressive strength of 55 MPa (7975psi) and a mean strength of about 70MPa (10,150 psi) at 90 days. Nofreeze-thaw or any other durabilityproblems exist. The high cementcontent helps reduce surface wear also.Austria has 28-day flexural strengthsranging from 6.5 to 9.5 MPa (942 to1378 psi) with mean of 7.5 MPa (1087psi) and Italy has a mean 28-dayflexural strength of 8.3 MPa (1203 psi)and a mean compressive strength of56.5 MPa (8193 psi).

l Lean Concrete in Spain l Lean Concrete Used for Shouldersor Emergency Lane

Lean concrete or cement-treated basesmust have a minimum compressivestrength of 8 MPa (1160 psi) at sevendays; or alternatively not less than 12MPa (1740 psi) at 90 days for slower-strength-gaining mixtures.

A French project had tied lean concreteshoulders that appeared to performvery well. This design reduced costs.

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l Thick Porous Concrete Slab

Some countries are developing thisdesign, such as the Netherlands andFrance where it is defined as a porousconcrete base surfaced with a free-draining concrete layer, having a totalthickness of 40 cm (16 in). Thesepavements substantially reduce trafficnoises and act as storm runoffreservoirs in urban areas. Thesepavements must be maintained toprevent clogging.

l Lower-Quality Aggregates inConcrete Slab with AC Overlay

France uses lower-quality localaggregates in concrete pavements forwhich an AC overlay is also to beplaced during construction. Thisreduces overall pavement costs in areaswhere only poor aggregates exist.There is little freeze-thaw cycling inthese areas.

l Recycled PCC Including RecycledAsphalt Concrete (RAP) Material

Austria has conducted laboratory testsand several large field projects wherethe old concrete slabs with ACoverlays have been recycled back intoregular concrete for pavement.Recycled concrete pieces are beingused as the coarse aggregate and thesand fraction used in cementstabilization of the existing granularsubbase. The crushed concreteparticles may contain up to 20 percentRAP particles without impairing thequality of the new concrete. However,only about 6 percent AC content isgenerally used because greater

amounts of RAP require largeramounts of cement and this becomesuneconomical. Recycling concrete withasphalt provides a more economicalmixture and a way to reuse RAPoverlay material.

Surfacings

l Emphasis on Reduction ofTire/Pavement Noise and Vibration

Many concrete pavements weretextured with transverse coarse tiningthat was very good for friction andhydroplaning but caused considerableroad noise and vibrations. Thistechnique is no longer used.

l Longitudinal Light Texturing forNoise Reduction on New Pavement

In Germany, significant noisereductions were achieved by creating alightly rough longitudinal texture,using a burlap drag, a longitudinalsmoother, and smaller top-sizedaggregates. This produces a noise levelabout the same as that of a porous ACsurface after a year. In Spain,low-noise surfacings are obtained usinga combination of longitudinal brushand comb, achieving both amicrotexture (with the brush) and amacrotexture (with the comb).

l Porous AC Surface for NoiseReduction of New or ExistingPavement

Many countries have used porous ACsurfaces for old and new concretepavements. It has some significantadvantages and disadvantages. The

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advantages of this design are thefollowing: it eliminates hydroplaning,eliminates tire spray, gives goodfriction resistance, has low tire/pavement noise emission, gives asmooth ride, does not have reflectioncracks, and waterproofs cracks inCRCP. Its limitations include asignificant decline in the noise-reducingeffect over time as the layer fills withmaterials, a relatively short life, andhigher deicing salt requirements toprevent icing. Unsafe conditions candevelop when icing cannot beprevented completely.

l Porous Concrete Surface for NoiseReduction on New Pavement

The Netherlands (see Figure 2.14) andFrance have constructed porousconcrete surfaces on newly constructedconcrete pavements that givesignificant reduction in noise levels.The porous concrete surface has manyof the advantages and disadvantageslisted for porous AC surfaces, but thistechnique is still under development.

Figure 2.14 Photo of porous concrete surfacing placed on JPCP in Netherlands.

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l Exposed Aggregate Surface forNoise Reduction on New Pavement

A surface texture with low rollingnoise and low vehicle vibration buthigh friction is achieved through atechnique for chemically exposingaggregate. This technique is usedextensively in several countries,including Belgium, Austria, theNetherlands, and France. In Belgium,after the paver passes, the surface isimmediately sprayed with a retarderwhich penetrates several millimetersinto the mortar. A polyethylene sheet

is then placed over the surface. Thisserves to protect the retarder from theeffects of inclement weather and toprotect the effectiveness up to themoment when the retarded surfacemortar is removed through specialwire brushing after 24 to 72 hours.The aggregate at the surface is thenexposed and has the desired surfacetexture to reduce rolling noise andvehicle vibration. The surface hasabout the same rolling noisecharacteristics as porous asphalt afterone year. A photo of an exposedaggregate surface is shown inFigure 2.15.

Figure 2.15 Photo of an exposed aggregate surface in France.

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In Austria and France, the exposedaggregate technique is similar,however, a major difference is that inAustria the slab is placed in two layersso that the top layer can contain a highquality, smaller aggregate (maximumsize 7 to 8 mm (0.27 to 0.31 in)) tomaximize noise reduction. The two-layer method is used in Austriabecause the aggregates that areresistant to wear and polishing areexpensive. The exposed aggregatesurface also provides a high level offriction resistance.

l Diamond Grinding Surface forNoise Reduction on New orExisting Pavement

This is used very successfully inBelgium to reduce noise over theoriginal coarse cross tining. It is alsoused in the Netherlands to reducenoise over original transverse brushtexture.

l Surface Layer of Epoxy/Aggregatefor Noise Reduction on ExistingPavement

The Netherlands uses an epoxy resinbinder applied to a hardened concretesurface, followed by a layer of crushed3- to 4mm (0.12 to 0.15-in) chromiumore slag (brand name Durop) andsurface rolling to produce a mosaic-likestructure. The Durop surface treatmentachieves large noise reduction relativeto the original brushed concretesurface. This treatment is comparableto porous asphalt.

l French Double Surface Treatmentfor Existing Pavement

A thin surface called a double layer isplaced to improve the rideability ofexisting pavements. The surfacetreatment consists of a spray ofpolymerized asphalt on the concretesurface, a layer of 1.4-cm (0.55 in)chips, and then a layer of l-cm (0.4-in)chips placed with no compaction.

l Overall Evaluation of Surfacings

Figure 216 shows a plot of noiseemission versus vehicle speed for oldconcrete surface (cross-tined), burlapdrag, and exposed aggregate asmeasured in Austria. These and otherdata show that old concrete has thehighest noise emission level, and theother treatments including porousasphalt, exposed aggregate andepoxy/ fine aggregate surface dressingare very similar.

Research and Development

The Study Tour was very impressedwith the pavement research programsunderway in most of the countriesvisited. Particularly impressive alsowas the very close workingrelationships that existed betweenpublic and private agencies.

l Close Government and IndustryRelationships

J In Belgium, close cooperation existsbetween government and industry.The development of the exposedaggregate surface is an example.

dB

1 0 0

95

9(

103.4

7 dB (A)98.8

/-//

/=-exposed aggregatemax size 7 mm (0.28 in)

.

I I I b60 80 loo

Speed - km/hr

Figure 2.16 Measured noise emissions for various surfacings in Austria.

J In Germany, Austria and theNetherlands, close cooperation existsbetween public and privateorganizations.

J The French national research studyon concrete pavements appears to bean ideal example of the closecooperation between public andprivate organizations. Privateorganizations add funding to some ofthese studies that they consider veryimportant. The great benefit of thisappears to be considerable innovationand results that actually get used onthe French highway system because allconcerned were involved in itsdevelopment.

l Accelerated Field Testing ofConcrete Pavements

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concrete pavement designs. The testtrack is part of the national researchproject in concrete pavements. TheStudy Tour observed the large testtrack in operation and saw some of theearly results obtained. One millionloads per month can be placed on theconcrete pavements.

l Higher R & D budgets than USA

It appears that in most Europeancountries the research effort underwaywas substantial. For example, theGerman cement institute has 4 timesthe budget of the USA’s PortlandCement Association (PCA) andAmerican Concrete PavementAssociation (ACPA) combined.

The French LCPC/Nantes circular testtrack shown in Figure 2.17 is anexcellent tool for accelerated testing of

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Figure 2.17 French LCPC/Nantes circular test track

l Willingness and Eagerness to TryNew Ideas

Europe has a very strong commitmentto research and development toimprove concrete pavements.Germany has continued to improve itsconcrete pavement designs over manyyears through research studies carriedout by government agencies anduniversities. The Netherlands is verywilling to try new ideas and fullydevelop them until they work.

In France, tremendous energy goes intoidentifying and developing new andinnovative ideas. One comment wasthat “the maintenance and growth ofthe competitiveness of concrete-based

road techniques depends on constantinnovation, the result of a partnershipbetween the industry and operatingauthorities.”

l Designated Percent of Constructionfor R & D

In Belgium, 0.8 percent of allconstruction projects goes to supportresearch studies.

l A Global View: ExportingTechnology by LicensingR & D Products

The French hold this point of viewvery strongly. Many developments bythe French national laboratory LCPC

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are subsequently licensed forcommercial use. Many products arejointly funded and developed.

l Implementation of Research

Dr. Sommer of the Austrian CementResearch Institute stated thatimplementation requires more effortthan the original research. He believesthat the researcher should guide thefield implementation until theprocedure is developed. This is aninteresting concept which woulddevelop a partnership betweenresearch and operations that is neededfor implementation.

Engineering Expertise

Solid groups of experienced pavementengineers exist in most of the countriesvisited. It appears that it is the generalpractice for individuals to make theircareer in pavement engineering. TheBelgium Road Research Center has anengineering group with many years ofpavement engineering experience. TheTechnical University of Munich has agroup of faculty and researchers thathave worked in pavement research formany years and are at the forefront ofpavement technology.

The French LCPC and SETRA havemany experienced pavement engineerswith careers dedicated to pavements.All French engineers in public worksgraduate from the same university.The French are clearly not satisfiedwith the status quo in pavementengineering. The French program ofcooperative research was veryimpressive to the Study Tour.

Many of these engineers have theability to travel to internationalconferences and serve on internationalcommittees (e.g., PIARC and TRB).

Toll Road Financing and Engineering

The Study Tour was very impressedwith the French toll road companies(COFIROUTE and SAPRR). France hasdepended heavily upon toll financingfor the development of their ruralmotorway system. Currently toll ratesare about 11 cents per mile or about 50percent higher than the USA averagetoll rate.

The pavements were in very goodcondition and COFIROUTE andSAPRR appeared to make efforts toprovide exceptional service to highwayusers. Feedback from users wasobtained continually and was used toimprove service levels. The tollagencies seek constant feedback frommotorists on pavement condition,safety, and various service area aspects.

Therefore, they choose their pavementdesigns based on both cost and quality-of-service considerations. High-qualitypavements mean a smooth, low-noisesurface and a safe ride. Adequatefunds are available to maintain thesepavements in a very good conditionand to construct pavements that willprovide a long service life with lowmaintenance. These pavements aremaintained in a better condition thanpavements which are not on toll roads.

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2.2 Implementation of PromisingTechnology in USA

The mission of the Study Tour includesthe development of appropriaterecommended actions for enhancingour nation’s highway system,productivity and economic future.Those technologies and ideas that mayshow promise for implementation aresummarized. in this section.

l Design-related Technology

J CRCP/Dowelled JPCP: Use a longdesign life (30-50 years) for heavilytrafficked highways, especially nearor in urban areas. Future disruptionof traffic will increase congestion andaccidents. Concrete mixtures can bedesigned and constructed with durablecharacteristics to last even longer thanthis time period. Note that thisrecommendation is also given in the1986 AASHTO Design Guide for urbanareas.

J JPCP/CRCP: Continue to refineprocedures for determining long-termincreases in truck volumes, axle loads,tire pressures and use of super singletires in pavement design. Within thisdecade the USA is likely to experiencethe types of truck loadings now seenon Europe’s highways.

J JPCP/CRCP: Emphasis should beon the total pavement system, not justthe thickness of the concrete slab.Concrete pavement design in the USAseems to focus on the slab thickness,which, based upon observations ofEuropean pavements, is not the mosteffective design. Actually, the facts

show that concrete pavement slabsbeing built in Europe today are notthicker than in the USA. However,they do have several design featureswhich more than adjust for the needfor thicker slabs, including thefollowing: thicker and more durablebases and subbases, bonding of treatedbases to the slab, interlayers to preventerosion, doweled joints clustered inwheel paths, widened traffic lanes, tiedconcrete shoulders, subdrainage andhigher concrete strength.

J JPCP: Unique German concretepavement design. This jointed plaindoweled concrete pavements designhas proven to give excellentperformance in Germany for manyyears. This design should be tested inthe USA to determine its cost,constructibility and performance.Actually, some pavements in the USAhave many of the same design featuresas the German design and haveperformed well. However it is thedetails (such as the bonding of the slabto the lean concrete base after jointingthe base) that often make or break thesuccess of a design.

J JPCP/CRCP: Thick granular layeron subgrade beneath treated base.This layer has the followingcharacteristics: 30-cm (12-in) thicknessor greater depending upon subgradesoil stability, adequate thickness toprotect against frost heave, and limitedfines content to allow for somedrainage through the layer. Thephilosophy in several Europeancountries is that this layer shouldprovide a certain minimum level ofsupport that is the same for all

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pavement types (a field bearing test isused to determine adequacy). Thisplate bearing test is not exactly thesame as the conventional test used inthe USA. The minimum requiredmodulus of elasticity as measured ontop of the granular layer appears torequire very good support on whichthe lean concrete base or CTB isconstructed.

J JPCP/CRCP: Catalog of designs.The design catalog has achievedwidespread popularity in Europe,probably for at least three mainreasons. First is the improvedcommunication of specific pavementdesigns to management, contractors,and agency construction personnel.Second, the designs in the catalog areoften the result of a combination ofboth theoretical analyses usingsophisticated procedures andprograms, and engineering andconstruction experience. Third, thedesign catalog can be easily modified.

Another reason, especially valuable forconcrete pavements, is that all of thedetails of the specific cross-section canbe provided including all transverseand longitudinal joints, load transfer,reinforcement, tie bars, drainage,shoulders, etc. to reduce the potentialof errors in construction. The exacttype of catalog and its format forsuccessful use in the USA must becarefully planned. Such a catalogwould help all involved in pavementsto focus on the best practices.

J JPCP/CRCP: Provide adequate full-width concrete and base pavingthickness for future traffic controlneeds during rehabilitation ofpavement or bridges or emergencies.Change the terminology from“shoulder” to “emergency lane” toreflect this design philosophy.

J JPCP/CRCP: Use widened trucklanes. The advantages of wideningtruck lanes by approximately 0.5 m(1.6 ft) include greatly reduced edgestresses to almost interior loadinglevels. This reduces transversecracking and reduces corner deflectionswhich cause erosion, faulting, anddiagonal/corner cracks. The beststructural design is to have both awidened traffic lane and an adjacenttied concrete shoulder/ emergency lane.Note that the paint strip must beplaced 0.5 m (1.6 ft) from the edge ofthe slab to achieve the benefits ofreducing critical edge loads by trucks.

J JPCP: Joint designs to improveperformance. Several transverse jointdesign improvements are describedbelow.

cr Notch or joint and then bond thelean concrete or cement-stabilized baseto the JPCP slab. The bonding of theselayers provides a thick monolithic slab,which decreases flexural edge stresses,deflections, thermal curling, moisturewarping and interlayer erosion leadingto faulting.

= Varying dowel placement acrosstraffic lane to concentrate on heavytruck wheelpaths to reduce costs.

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BS Short (5-m (16.54) joint spacingused for JPCP over treated bases.

* Required use of dowel bars tocontrol faulting for heavy traffic.(These are already used by mostagencies in the USA.)

* Plastic coating on dowels and centerthird of deformed tie bars, as done inGermany. Epoxy-coated dowels areused extensively in the USA; however,the plastic coating used in Germanyappeared to be quite substantial.

J CRCP: Longitudinal reinforcement.CRCP has performed extremely well inEurope (Belgium, Spain, France) formany years and has been built recentlyin several other countries. Somereasons for its good performance:

rt Increased steel (0.85 percent) hasgiven excellent long-term performanceon many projects in Belgium and a fewprojects in France (0.72 percent) andSpain (0.73 to 0.85 percent).

w Steel placed closer to the surfacewill hold cracks tighter and greatlyreduce punchout development. This isthe experience of European engineersand experimental sections in the USAhave shown the same results.

m Rectangular, coilable steel strips(product name FLEXARM) should betested in the USA to assess theiradvantages and performance. The steelpercentage must be carefully designedfor USA conditions.

J JPCP/CRCP: Two-layer slabconstruction. This is an economicaldesign, especially where either alongitudinal brush texture or exposedaggregate surface is desired andsuitable hard aggregates are veryexpensive, or where local aggregatesare too soft to be used for the surfacelayer. The water/cement ratios of thetwo layers must be equal.

J JPCP/CRCP: AC layer between theconcrete slab and a treated base ifnotching or jointing is not done. Thepurpose of this layer is to reduceerosion between the slab and treatedbase. This has been tried in the USAin at least one State and stripping ofthe AC layer occurred. However, moreeffective anti-stripping tests andremedies are now available. Thisalternative deserves consideration byagencies unwilling to notch and bondlean concrete bases to the slab.

J JPCP/CRCP: Trapezoidal cross-section. This design has hadwidespread use in two countries. Itbasically provides, for the same cost,an additional safety factor forstructural fatigue. For example, if afour-lane divided freeway pavementdesign requires a 25-cm (10 in) slabthickness for the outer lane, providinga slab that varies from 22 mm to 28 cm(9 to 11 in) from the edge of the innerlane to the edge of the outer lanewould provide considerably morestructural reliability at the thickenedlongitudinal edge (28 versus 25 cm (11versus 10 in)). The lanes must, ofcourse, have adequate tie bars to holdthe slabs together tightly and maintaingood aggregate interlock

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J JPCP/CRCP: Geotextile drainagefabric between slab and base. Theperformance of this interesting designis not documented yet. This was beingplaced in France between the CRCPand the existing dense aggregatesubbase of an old AC pavement. Thethick fabric is supposed to provideboth a filter to inhibit fines movementand a permeable layer to removemoisture.

J JPCP/CRCP: Porous concrete baseunder shoulder. This alternativeseems to be very practical and usefulto help drain the pavement section.An appropriate drainage system mustexist for the porous layer.

J JPCP/CRCP: Longitudinal edgedrains connected to closed drainagesystem. This German system of drainsprovided for both surface water andsubsurface water drainage.

J JPCP/CRCP: Ditch line a minimumof one meter from the bottom of thebase. This design should reduce theamount of water in the base layer andat the top of the subbase.

J JPCP/CRCP: Solutions for bridgeapproaches. Two interesting solutionsto the problems of excessive pavementend movement and settlements atbridges were observed.

r% End lug to protect structure and ACtransition surface layer that can beeasily leveled up.

w Paving directly over the bridge deckwhere the bridge is designed for theextra dead load.

l Construction-related Technology

J Warranties for pavementconstruction work. While warrantiesranging from one to nine years arebeing used in Europe for variousaspects of pavement construction, therewas not adequate information availableto assess their impact. Much morespecific information is needed aboutthe details of these warranties.Implementation of warranties wouldneed a long phase-in period in theUSA.

J Construct straight cross slope withno crown across traffic lanes. Thistechnique should provide improvedrideability. A 2.5-percent slope, usedin Europe, may improve surfacedrainage also.

J Liquidated damages = Incentivesrate per day for a given constructionproject time limitation. Contractorsfelt that this was a fair specification.

J Prevention of joint reservoirsawing residue from entering joint.The practice of using a long rubberband stretched across the joint andsqueezed into the first narrow cutappeared to be simple and effective.

J Two-layer paving equipment.Paving equipment capable of placingtwo separate concrete mixes with asingle pass is available.

J Re-bar tubes placed behindvibrators for CRCP. This shouldimprove positioning of bars, but needsfurther study.

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J Lean concrete used for temporarywidening for traffic control. TheBerlin A10 project included a leanconcrete traffic lane placed adjacent tothe existing old concrete pavement toincrease the number of traffic lanesduring construction. This lane wasultimately recycled along with the restof the adjacent older concrete afterfulfilling its purpose. This techniquemay be cost-effective on some projects.

l Maintenance and RehabilitationRelated Technology

J Unbonded CRCP and JPCPconcrete overlays of existing concretepavements. Designs includedfracturing the existing concrete (piecesless than 0.5 m (1.6 ft)) and placing aninterlayer of one of the following: thinAC, lean concrete, or thick geotextilefabric. Excellent performance wasachieved in several countries.

J JPCP and Fiberized concreteoverlays of existing AC pavements.This is potentially a cost-effective long-term solution for badly cracked orrutted AC pavements. Constructionprocedures are standard for JPCP andperformance has been good. Fibrousconcrete overlays of AC pavementshave worked well in Belgium.

J Complete recycling of concrete andother materials on the job site. Thisrequirement may become standardpractice in densely populated areas ofthe USA, as it currently is in someEuropean countries due toenvironmental concerns (shortage oflandfill space, etc.)

J Rehabilitate pavements at a highercondition level. European agenciesappear to rehabilitate pavements athigher levels of condition than USAagencies. This may have significantuser-related, economic, and structuralbenefits for the infrastructure over thelong run.

J Lane reconstruction designs. TheFrench and German designs are quitedifferent but both have some veryinteresting features that should be ofinterest in the USA. Lanereconstruction would be useful onmany USA pavements where only theouter one or two lanes are badlydeteriorated.

J Lane replacement or addition forAC pavements. Replacement of anexisting deteriorated AC pavementouter truck lane with concrete orconstruction of an additional outer lanewith concrete pavement to serve heavytruck traffic has worked well in Franceand has applicability in the USA.

JFrench LCPC/Freyssinet loadtransverse devices. Extensive researchshows that this device is effective inrestoring load transfer. The cost-effectiveness is unknown.

l Concrete Materials-RelatedTechnology

J Improved concrete quality controlfor durability. The absence of concretedurability problems in Europe speaksfor itself in comparison to the manydurability problems from “D” cracking,ASR and freeze-thaw spalling in theUSA. Further investigation is needed

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of the specific QC programs in variouscountries such as Germany, Austriaand Switzerland which have colderclimates. Rapid determination (withinan hour) of the air void system usingfresh concrete in Germany (using theDenmark equipment) was impressive,as well as Switzerland’s determinationof the air void system in hardenedconcrete from cores in 36 hours.

J Higher-strength concrete forpavements. Several Europeancountries are routinely specifyinghigher-strength concrete. Belgiumspecifies a minimum compressivestrength minimum of 55 MPa (7975psi). This results in a typical mean of70 MPa (10,150 psi) at 90 days. Typicalflexural strengths have a mean of 7.5MPa (1,087 psi) in third-point loadingat 28 days. The extremely good long-term performance of these concretepavements is due in part to their highstrength.

J Thick porous concrete slab. AFrench technological forecastingcommittee concluded that a free-draining surface would be a majorimprovement due to its noisereduction, elimination of hydroplaningand storm runoff reservoir capabilities.At least one street has been built inParis having a porous slab about 40 cm(16 in) thick Further research isneeded.

J Recycling concrete that includesAC material. This technique wouldreduce the cost of recycling concrete

back into concrete, particularly wherean AC overlay exists over a concreteslab. Extensive research in Austriashows that a limited amount of AC isnot detrimental to a concrete mixture.A few recycling projects containing ACparticles have been completed in theUSA.

J Lean concrete used for shoulders(or emergency lanes) and lanewidening during traffic control. Theremany be several innovative uses ‘forlower-strength and lower-cost concrete.

J Fibrous PCC (steel fibers). The thinfibrous concrete overlay of a rutted ACpavement in Belgium was impressive.Some of these have been built in theUSA also.

l Surfacings-Related Technology

J Longitudinal light texturing fornoise reduction. Several differentlongitudinal methods are being usedthat significantly reduce noise levelsyet still provide adequate friction.

* Longitudinal texturing producedwith a burlap drag and smaller top-sized aggregates produce low noiselevels in Germany.

w Longitudinal texturing produced bya combination of brush and combachieves both microtexture andmacrotexture (initial grooves were 0.7to 1 mm (0.027 to 0.039 in) deep),which produces low noise levels inSpain.

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J Porous surfacings. These surfacesproduce the lowest noise levels, give asmooth ride, eliminate splash andhydroplaning, and provide goodfriction capabilities, but their life isshort and they clog with fines.

* Porous AC surface (with polymer) 4cm (1.6 in) thick Many countries haveused a porous AC surface for old andnew concrete pavements. It has somesignificant disadvantages such asclogging, poor durability and black iceformation in winter.

m Porous concrete (with polymer)surface 4 cm (1.6 in) thick. This hasbeen built in at least two countries. Italso has the same clogging problem asthe porous AC surface but may have alonger life.

J Exposed aggregate surface. Asurface texture with low rolling noiseand low vehicle vibration but highfriction is achieved through thechemically exposed aggregatetechnique. This surface has beenshown to have a long life. It can beaccomplished most economically usinga two-layer slab with smaller hardaggregates in the upper layer or a hardaggregate of somewhat smallermaximum size through the full slabdepth.

J Diamond grinding surface fornoise reduction (existing pavement).Longitudinal grinding reduces noise.

J Surface layer of epoxy/fine grainedaggregate for noise reduction (existingpavement). An epoxy resin binder isapplied to a hardened concrete surface,

followed by a layer of crushed 3- to4-mm (0.12- to 0.16-in) chromium oreslag, and the surface is then rolled toproduce a mosaic-like structure with alow noise level.

J French double surface treatment(existing pavement). A thin surfaceconsists of a spray of polymerizedasphalt on the concrete surface, a layerof 1.4-cm (0.55in) chips, and then alayer of l-cm (0.4 in) chips placed withno compaction. This surface treatmentreduces noise significantly.

l Research and Development RelatedTechnology

J Closer government and industrycooperation. It is obvious that Europebenefits greatly from close cooperationbetween public and privateorganizations. Cooperation is growingin the USA. The existence of closeworking relationships among industry,State, and Federal officials is one of thereasons why this tour took place.Institutionally, the USA needs to keepthe momentum going by supportingactivities such as the AASHTO-ARTBA-AGC Joint Task Force;industry involvement in research andtechnology advisory efforts with TRB,NCHRP, and FHWA TechnicalWorking Groups and Expert TaskGroups; the University TransportationCenters; and expanded partnerships inresearch agreements throughimplementation of the Stevenson-Wydler Technology Innovation Act of1980 (ISTEA Sec 6001).

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The great benefit of close interactionbetween groups appears to beconsiderable innovation and practicalresults that actually get used on thehighways because all concerned wereinvolved in their development andhave a stake in their success.

J Construction of selected Europeanconcrete pavement designs in theUSA to evaluate constructibility, costs,and performance. Several highlypromising candidates are available.Note that different surfacings could betested for any of these designs. Thedesign and construction of severalinnovative European sections isrecommended.

rt The German design for JPCP hasprovided many years of excellentperformance. The construction of theGerman section in Michigan is fullysupported and should lead to specialattention to increase foundationsupport.

= The Belgian design for CRCP (withthe higher steel content) has performedfor over 20 years under heavy trafficwith no punchouts.

J The French trapezoidal CRCP orJPCP design (one or two layers) hasbeen used extensively for one- to two-lane replacements with good success.

J The Austrian JPCP design with twolayers is being constructed on manyheavily trafficked highways.

The SHRP SPS-2 effort might beemployed for at least some projects.

J Accelerated field testing of concretepavements. The French LCPC / Nantescircular test track is currently testing avariety of concrete slab designs. It isrecommended that a task group beformed to determine the USA needs inaccelerated performance testing ofconcrete pavements. After the testingneeds have been identified, the taskgroup should develop a proposaloutlining the requirements andprocedures required to meet theseneeds.

J Increased R & D budgets forpavements. Most European countriesappear to be conducting morepavement research than the USA, as apercentage of total funding spent onthe highway network The StrategicHighway Research Program (SHRP)was a recent step forward to increasedfunding for pavement-related R & D,and now the new 1991 highway bill(ISTEA) provides additional R & D forhighway research. The increasedexpenditures for R & D through ISTEAin both HP & R funding and in theNCHRP program are also very positivemovements. This trend towardsincreased funding for highway R&Dneeds to continue. It would behoovethe pavement-related industries tomake a very strong case for the needsand the benefits of pavement researchin order to obtain a fair share of thisfunding. While much of the funding isrelated to federal investment, moreprivate sector funding, industrypartnerships and implementation of thepreviously mentioned Stevenson-Wydler Technology Innovation Act of1980 (ISTEA Sec 6001) can help stretchthe funds.

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J Innovation, willingness, andeagerness to try new ideas. State andlocal highway agencies arecomplemented on their increasedcommitment to research anddevelopment in improving concretepavements as are similar organizationsin Europe. In addition, an increasedeffort needs to be made in the USA forinnovation in all aspects of pavementengineering as is being done incountries like France.

J Global view: exporting technologyby licensing R & D products. TheFrench hold this point of view verystrongly. Many developments by theFrench national LCPC laboratory aresubsequently licensed for commercialusage. Many products are jointlyfunded and developed. FHWA’srecent opening of foreign exchangeprograms with Europe and Asia are tobe complemented. The joining ofPIARC, especially, is much appreciated.To help the American economy, wemust continue to develop a global viewof the enormous benefits in developingimproved pavement designs,construction specifications andtechniques, equipment, maintenanceand rehabilitation designs andespecially improved materials.

J Implementation of research. Itmust be realized that the level of effortneeded to implement any procedure orproduct developed under a researchstudy is significant, and may be severaltimes more than the original researchstudy. The researcher should guidethe field implementation along with ateam of engineers from operations andindustry until the procedure or product

is working as intended. This conceptcould help develop a partnershipbetween research and operations that isneeded for successful implementation.The increased funding and recentreorganization of FHWA’s office ofTechnology Applications is a verypositive step forward, as is FHWA’sgeneral direction toward a moretechnology-centered mission.

l Improving Engineering Expertise

With the complex changes that haveoccurred in pavement engineering -rehabilitation strategies, new materials,life-cycle costs, user costs, weigh-in-motion data, remaining life concepts,increased and varied truck traffic, andnow feedback from pavementmanagement systems - it is obviousthat the education of the country’s nextgeneration of pavement engineer needsto be restructured. Needs include:

J Improved pavement engineeringeducation in colleges and universities.

J Additional short courses in allaspects of pavement engineering forpracticing engineers and constructionand maintenance personnel.

J Increased priority in public andprivate organizations for training theirstaff in pavement engineering andconstruction.

J Increased interaction of pavementengineers and construction personnel,within States, regionally, andnationally. Additional travel fundsmust be made available for thisimportant activity.

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J Establish at the national level afocal point for collecting informationabout developments in the USA andother nations in pavement technology,and distributing the information topavement engineers, researchers, andthe construction industry. This effortshould include and could be basedupon the continuing SHRP effort, andshould include a broad-based advisoryb o a r d .

2.3 Benefits to the USA ofImplementing Some InnovativeTechnology

Looking for a moment at the BIGbroad picture of the nation in thecontext of what the Study Tourexperienced in Europe, the followingthoughts about the benefits ofimplementing the aboverecommendations emerged from theStudy Tour participants.

l Improved pavements will result infewer lane closures for pavementrepairs: reducing congestion and itsassociated problems (i.e., wasted time,delivery delays, accidents, air pollution,and fuel consumption).

l Improved pavements will result infewer accidents, injuries and fatalitiesdue to improved pavement surfacesand fewer lane closures, which alwaysincrease the potential for accidents.

l Improved pavements will increasedriver and passenger comfort anddecrease vehicle user costs due tosmoother, quieter surfaces and alsofewer traffic delays from lane closures.

l Improved pavements will provide ina much more efficient highwaytransportation system overall that willgreatly contribute to economic growthand help to keep the USA competitivewith Europe, Japan and other countrieswith highly efficient transportationsystems.

Concrete pavements will play animportant role in the continuingimprovement of the nation’s highway,street and airport system, especially inlight of growth in truck and aircrafttraffic volumes and weights. This isalso the belief of many pavementexperts in Europe. However, new andinnovative technology and training isneeded, along with implementation ofthese innovations, to provide improveddesigns, materials, construction qualityand rehabilitation of these pavements.To that end this report is dedicated.

l Improved pavements will improveenvironmental conditions for peopleliving and working near highways dueto reduced noise levels and reduced airpollution from less congestion.