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3.2 Austria

l Concrete Pavements in Austria

Austria began constructing concretepavements in the 1940’s and hasconstructed both JPCP and JRCP.Today many pavements older than 30years and some 50 years old exist inAustria. The following table shows theextent of concrete pavements onAustria’s main highways.

Table 3.1 Austrian highway mileage.

11 Asphalt concrete 1 834 1II -

I 1I I II

II Concrete 1 698 1 4 6 IIII Total 1 1532 1 100 11

1 km = 0.621 mi

However, studded tires caused ruts of2 to 3 mm (0.08 to 0.12 in) in the olderpavements. Because Austria has a lotof ram some type of rehabilitation hadto be performed. A thin polymerizedasphalt layer has been placed over thetruck lanes of many older concretepavements to repair the studded tiredamage. This layer has a life of onlyfour to six years.

l Designs

J 18-22 cm (7-9 in) JPCP (25 cm (10 in)for heavy traffic)J 5 cm (2-in) AC interlayerJ 20-45 cm (8-18 in) untreatedgranular layer with less than 3 percentfines

J 18-22 cm (7-9 in) JPCPJ 5 cm (2 in) interlayer ACJ 18-20 mm (7-8 in) cement-treatedbase (only past five years)

The thickness values in the designcatalog are based upon a minimumbearing capacity on the subgrade asdetermined by plate loading tests onsite and defined as an acceptance limitin Austrian Specification RVS 8.24.The minimum bearing value is 35 MPa(5075 psi). If the soil does not achievethis level of bearing, soil stabilization,soil replacement by better materials orother methods to achieve the bearingcapacity is required. The minimumbearing capacity for asphalt andconcrete pavements is the same. Thefrost depth in Austria is 1.5 m (4.9 ft).

The typical joint spacing is 6 m (20 ft)for a 25-cm (10-in) slab. Dowels are 2.6cm (1 in) in diameter and 50 cm (20 in)in length. For heavier traffic, themaximum joint spacing, in meters, is25 T, where T is the slab thickness inmillimeters. Thus, a maximum jointspacing for a 25-cm (10-in) slab is6.25 m (20.5 ft).

Austria has developed a catalog ofpavement designs for a 30-year period.Four different designs are considered:dowelled and undowelled withuntreated granular base or cement-treated base. Ranges of current designthickness are as follows.

Faulting of transverse joints is wellcontrolled by dowels, which areessential. Austria found that dowelsmust be coated to prevent corrosion.On some early projects, dowels werenot coated and corrosion was serious.

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In the late 1970’s, the sealing practicechanged in some areas of the country.The initial saw cut for transverse andlongitudinal joints was made 3 mm(0.12 in) wide and the joint was notsealed. This practice saved about 10percent of the construction cost. Thereis controversy about this because someprojects are sealed even today, andsome feeling is that joint sealing wouldadd life to the concrete pavement.

Included in the JPCP thickness is a4cm (1.6 in) top layer of smaller-sizedhard aggregate that is used to providea low-noise, high-friction texture. Thesurface aggregates are exposed duringconstruction as described later.Structural design for, pavements onbridge decks and in tunnels is alsogiven in catalogs.

The full-width paving is 11.5 m(37.7 ft), and includes an inner laneand narrow shoulder of 4.75 m (15.6ft), an outer lane of 3.75 m (12.3 ft) anda tied shoulder of 3.00 m (9.8 ft). Thecross-slope of old pavements was 1.5percent, but now all new pavementshave 2.5 percent slope.

l Rehabilitation

Austria has tried several different waysto rehabilitate their concretepavements. A few projects have beencracked and seated and overlaid withAC. An unbonded concrete overlaywas recently placed on an oldpavement with a 5-cm (2-in) ACseparation layer. Its performance wasvery good, but it was found that it wasmore economical to recycle allpavement materials and reconstruct thepavement into either concrete orasphalt.

For rehabilitation projects, all sitematerials were recycled back into therehabilitated pavement. Old concreteis recycled into a new concrete slab.Old aggregate base is used as part of anew cement-treated base. Old AC iscrushed, some is used in new recycledconcrete, and the remainder is used inthe 5-cm (2-in) AC interlayer betweenthe slab and cement-treated base.

See the project site description belowfor details of some rehabilitationprojects.

l Noise Pollution

Increased sensitivity of Austrians withregard to traffic noise has resulted in amajor noise-reducing efforts over thepast decade through use of noisebarriers, low-noise freight vehicles, andnew low-noise pavement surfacings.Several surfacing techniques have beenevaluated in Austria.

Porous asphalt surfacing was firstconstructed in Austria in 1984 and a lothas been constructed since that time.Measurements have shown that thissurfacing initially reduces tire noiseemission by 4 to 6 dB(A) at 100 km/hr(62 mi/hr) compared to conventionalasphalt or concrete pavements,respectively. The porous surface alsoreduces hydroplaning and splashduring rainstorms. However, problemshave developed with this surfacing.Older porous asphalt surfaces haveshown a significant decline in thenoise-reducing effect due to the voidsfilling up with soil and abrasives andfurther compaction. (4) Porous asphaltwould therefore need to be cleaned

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over time to maintain its low-noisecharacteristics. Another concern is thatdeicing salt requirement is about 15 to50 percent higher to prevent icing.Even then icing cannot be preventedcompletely under critical weatherconditions, such as freezing rain. (4, 6)

The use of slipform pavers with asuper-smoother flattens any transversewaves reduced noise by 2 dB(A).Further improvements by 1 to 2 dB(A)were achieved by creating a fine-roughlongitudinal texture using a burlapdrag, instead of the formerly commontransverse brushing with a broom. (4)The burlap drag is simple andinexpensive, but friction resistance islower than with a transverse broomfinish. Higher friction resistance can beobtained but the concrete must be richin mortar and longitudinal grooves2 mm (0.08 in) deep must be madeusing a plastic brush or metal tines. (6)

The exposed aggregate technique issimilar to that described in Belgium.The main difference is that in Austriathe slab is placed in two layers so thatthe top layer can contain a highquality, smaller aggregate (maximumsize 7-8 mm (0.27-0.31 in)) to maximizenoise reduction. The two-layer methodis used in Austria because theaggregates that are resistant to wearand polishing are expensive. Thistechnique was first constructed inAustria in 1990 with another four sitesin 1991. This technique reduces noiseemission through provision of atextured surface with selected hardaggregates in the upper 4 cm (1.6 in) ofthe slab, as shown in Figure 2.8. Thesurface is sprayed with a retarder,covered with plastic sheeting to

prevent evaporation and the finemortar on the surface is removed bybrushing the next day, or acombination of a retarder/curingcompound is used. (6)

Optimum noise reduction requires thatthe maximum aggregate size should be7-8 mm (0.27-O-31 in) and the percentof particles 4-7 mm (0.16-0.27 in) or 4-8mm (0.X-0.31 in) should be as high aspossible, but there must be enoughmortar between the particles to ensureexcellent bond. The w/c ratio shouldbe well below 0.40 and texture depthshould not exceed 1.2 mm (0.05 in).The stone particles must consist of awear- and friction-resistant material.In Austria, a 4-cm (1.6-in) top layer isconstructed with the aggregatescontaining the above characteristics.

Figure 2.16 shows the beneficial effectof the exposed aggregate surface onnoise emission reduction of as much as7 dB(A) from that of old concrete. Theexposed aggregate noise emissions arecomparable to that of porous asphaltsurfaces. Exposed aggregate is notlikely to loose its noise-reducingproperties as the porous asphalt does.

The exposed aggregate surface alsoprovides a high level of frictionresistance. (6)

During the trip along the Al freewayfrom Vienna to Salzburg the StudyTour stopped at the beginning of anew concrete section with the exposedaggregate surface. This section wasadjacent a section with a porus asphaltsurface. There was no discernabledifference in traffic noise between thetwo sections. Both were very quiet.

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Some additional details are givenunder the Al project site description.

l Concrete Materials andConstruction

Concrete quality appeared to beexcellent in Austria even though manyfreeze-thaw cycles occur and a lot ofdeicing salt is used. There are noreported occurrences of “D” cracking orASR and only a few freeze-thawdurability problems. Cores from oldconcrete pavements have 100 MPa(14,500 psi) compressive strength.

All concrete mixes must be approvedby an authorized and accreditedlaboratory.

Concrete compressive strength isspecified to be more than 35 MPa (5075psi) for the lower concrete layer andmore than 40 MPa (5800 psi) for thetop layer after curing for 28 days. Theflexural strength must be 5.5 MPa (798psi) for 12 by 12 by 36-cm (4.7- by4.7- by 14in) beams in center-pointloading. Austria believes primarily inthe flexural strength test for concretepavements.

The air void bubble spacing must beless than 0.22 mm (0.0087 in) and totalentrained air content must exceed 2.0percent.

Whenever concrete slabs are removedfor rehabilitation, they are recycled intoconcrete or some other use on theproject site. The maximum particlesize is 3.2 cm (1.25 in) and natural sandis added to the mix.

Laboratory tests have shown thatparticles from old concrete pavementsare better than many naturalaggregates. The recycled concrete wassuperior to normal concrete made fromgravel. Coarse recycled concrete from4 to 32 mm (0.16 to 1.25 in) is beingused as the coarse aggregate, theparticles finer than 4 mm (0.16 in) areused for mixing with the in situsubbase (prior to cement stabilization).

In addition, the crushed concreteparticles may contain up to 20 percentAC particles (originating from existingAC overlays on the concrete pavement)without essentially impairing thequality of the new concrete. Thistechnique has been used on threereconstruction sites of the Al freewayalthough the percent of asphalt hasbeen only 4 to 6 percent. Figure 3.5shows a section of a concrete mixturecontaining AC material. This providesa more economical mixture and a wayto reuse old AC material which isusually taken from thin AC overlays ofconcrete pavements. Extensiveresearch on concrete recycling has beenconduced by Dr. Sommer of theResearch Institute of the AustrianCement Maker’s Association. (3)

l Project Sites Observed

One recently completed project andtwo under construction were observedby the Study Tour on the Al freewaywhich connects Vienna with Salzburg.This 300-km (186-mi) highway is aheavily trafficked east-west highway.It was all constructed of JRCP over 20years ago, and some of it is over 30years old. (2)

7 1

Figure 3.5 Cut section of an Austrian recycled concrete mixturecontaining old AC overlay material.

Al Freeway Unbonded ConcreteOverlay. The original 1957 JRCP hada 24-cm (9.5-in) slab and 3 cm (1.2 in)of sand over an aggregate base. Theold slab was cracked and seated, 5 cm(2 in) of AC was placed, and then a 20-cm (8-in) JPCP overlay was placed. (2)

Al Freeway Recycling andReconstruction. The original JRCP(some portions included a thin ACoverlay) was shattered using a WirtgenGuillotine, hauled to a crushing planton site and processed into severalfractions. These fractions containbetween 2 and 10 percent AC from thethin AC surface which was included inthe recycled concrete (about 6 percentaverage was old AC material). The O-to 3-mm (0- to 0.12in) fine fractionwas placed on top of the old gravelsubbase which contained 15 percent

fines and the material was thenstabilized in-place to a depth of 20-25cm (8-10 in) with cement using aBomag machine. The compressivestrength requirement was 3 MPa (435psi) at 7 days. A 5-cm (2-in) AC layer(which included some recycled asphaltpavement) was placed on top of thecement-stabilized layer to provide theconcrete pavement with an erosion-resistant base. (3)

A JPCP 25 cm (10 in) thick withdowelled joints spaced at 5.5 m (18 ft)was placed using a slipform paver.Plastic-coated dowel bars, 26 mm (1 in)in diameter and 50 cm (20 in) long,were spaced at variable locations, 11 inthe truck lane, 7 in the passing laneand 4 in the shoulder. The contractionjoints were sawn 3 mm wide and left

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t ransverse contraction joint 8 mm (0.3 in) sealed orlongi tudina l jo in t } 3 mm (0.1 in) unsealed

14 mm dia (0.5 in)

:o”( 0-J

‘4 cm (1.6 in) exposed smallsize aggregate concrete“V ”

18-21 cm (7-8 in)

Figure 3.6 Cross-section of Austrian JPCP reconstruction on the Al.

unfilled on this project. Note that onsome projects the joints are sawn 8 mm(0.3 in) wide and sealed with abituminous filler. Paving width was11.5 m (38 ft). (3) Figure 3.6 shows across-section of the completedpavement.

The slab was designed to have twolayers: a bottom layer of recycledconcrete and a top layer with high-quality hard aggregate (calledchippings) to provide a low-noise, highfriction surface. The slab was placed intwo layers by a single modified“double-decker” Wirtgen slipformpaver. This paver placed two separatelayers of slipformed concrete “wet-on-wet” to form a monolithic structure. (5)The Wirtgen SP1600 slipform paverwith the integrated two-layer pavingkit performed the following operations:

Bottom Layer (21 cm (8.5 in)):

J Spread the top layer concrete overfull width (11.5 m (38 ft)),J Liquify and compact the bottomlayer,J Form the bottom layer by extrusion,4 Insert the dowel bars at transversejoints,J Insert the tie-bars on longitudinaljoints, andJ Restore the surface of the bottomconcrete slab after insertion of dowelsand tie bars with the first oscillatingbeam.

Top Layer (4 cm (1.6 in)):

J Convey top layer concrete fromtruck mixer over the paver main frameand discharge into a hopper feeding inthe spreading augers,

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J Liquify and compact the secondlayer with a high-frequency vibrationsystem (vibration is controlled infrequency to avoid causing additionalvibration to the bottom layer),J Form the top layer by extrusion, andJ Finish the top layer with a secondoscillating beam and the supersmoother.

The 21-cm (8.5-in) bottom layercontained the recycled crushedconcrete plus natural sand. Cementcontent was about 360 kg/m3 (607pounds/yd3) and also containedentrained air (3.5 percent). The flexuralstrength at 28 days ranged from 6.5 to9.5 MPa (942 to 1378 psi) with a meanof 7.75 MPa(1124 psi).

The top 4-cm (1.6-in) layer contained ahigh percentage (65 percent) of hardstone chippings having a maximumsize of 8 mm (0.3 in) and about 35percent sand (O-l mm (O-0.04 in)).Cement content was 450 kg/m3 (758pounds/yd3). The mixture had airentrainment (4 percent), plasticizer,retarder and a water/cement ratio of0.38 for durability and low shrinkage.A retarder was used for the topconcrete to prevent it from stiffeningmore quickly than the bottom concrete.The stone chippings (4-8 mm (0.16-0.31in)) had an LA abrasion value of lessthan 19 and a polished stone valuegreater than 50. The surface of theconcrete was sprayed with a retarderand covered with a plastic sheeting orsprayed with a film-forming curingcompound to prevent evaporation.The next day the surface was brushedto expose the chippings and sprayedwith a curing compound. Texturedepth was about 0.9 mm (0.035 in) bythe sand patch measurement method.

A discussion of the noise characteristicsof this surface was previously given.Smoothness specifications were appliedusing a profilometer. Joint sawing wasdone through the plastic sheeting.

The concrete crusher and plant thatproduces the lower recycled concretelayer was visited. Approximately 10percent recycled AC is included in theconcrete mixture. The specificationsallow up to 20 percent but this requirestoo large a cement content to beeconomical. A separate plant mixesthe top layer. Only recycled concrete isused for the coarse aggregate in thelower layer.

Al Freeway Salzburg Recycling andReconstruction. This 17-km (10.6mi)project was nearly identical to theprevious Al freeway project. Trucktraffic was heavy on this section (3500per day). The original JRCP wasoverlaid with a thin AC overlay whichwas sawed and sealed. This layer wasdebonding from the slab and largepieces were coming off, whichprecipitated the rehabilitation. Thisproject was to be completed in 26weeks and the bonus per day andpenalty per day were equal. The studytour observed the old concretepavement removal process, whichincluded slab fracturing and a largebackhoe loading pieces of concrete intoa truck Figure 2.8 shows a photo of acore from this project. Figure 3.6shows a cross section of the slabshowing the recycled concrete base andthe top surfacing for noise reduction.The westbound lanes, shown in Figure3.7, had been completed the previousyear.

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Figure 3.7 Photo of the Al recycled concrete pavement near Salzburg, Austria.

l Traffic Loadings

The Austrian freeways carry heavytraffic loadings. The typical ADT is25,000 (up to 100,000) with an averageof 12 percent trucks. The growth ratein highway freight transport is high(7 percent per year). The single-axleload limit is 10 t (22,046 pounds) andthe tandem-axle limit is 16 tons (35,300pounds). A large number of overloadsexist. Austria is likely to increase itslegal axle weights to the 11.5 t (25,353pounds) EC maximum for single axles.

Concrete pavements are designed for30 years of traffic, taking intoconsideration different traffic lanes,distribution within traffic lane (from0.6 for a lane more than 3.5 m (11.5 ft),to 0.9 for 3-3.5 m (10-11.5 ft), to 1.0 fora lane less than 3.0 m (10 ft)), theannual growth rate, and the design

period. Equivalency factors are used tocalculated equivalent single-axles of a10-ton (22,046 pounds) standard single-axle.

l Summary for Austria

Austria has constructed many jointedplain and reinforced concretepavements since the 1950’s which haveperformed very well under heavy trucktraffic. Studded tire damage causedsevere problems resulting in therequirement to place thin polymerizedAC overlays on the truck lanes. Theold pavements have excellent concretedurability.

The current design for new orreconstructed pavements is for short-jointed dowelled JPCP with tiedconcrete shoulders and a thin AC layerbetween the slab and the granular or

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cement-treated base. Rehabilitation, l Austrian Referencesincluding unbonded JPCP overlays onfractured slabs and AC overlays onfractured slabs, is underway on manyold pavements. The most usedtechnique to date has been thecomplete recycling of an old concretepavement into a new concretepavement with a full 11.5-m (38-ft)width.

1.

2.There is a very strong emphasis onhighway noise reduction in Austria.The use of the exposed aggregatesurface in conjunction with the two-layer slabs (the top layer containingsmall hard aggregates) has shownsignificantly reduced noise levels andhigh friction, 3.

Dr. Sommer of the Cement ResearchInstitute stated that the level of effortneeded to implement something (get itworking) is greater than the originalresearch effort. He believes that theresearcher should guide the fieldimplementation until the procedure isdeveloped. This is an interestingconcept which should develop aneeded partnership between researchand operations.

4.

5.

6.

Litzka, J. and G. Herbst, “A NewSpecification for the StructuralDesign of Pavements in Austria,”Proceedings: 1986 InternationalConference on Bearing Capacityof Roads and Airfields,Plymouth, England.

Breyer, G., M. Fuchs, J. Litzka,A. Molenaar and G. Nievelt,“Survey of ReconstructionMethods of Worn-Out (Aged)Rigid Pavements,” TechnicalReport, Federal Ministry ofEconomic Affairs, Austria, 1992.

Sommer, H., “ReconstructionJob-Sites 1991 on the MoterwayVienna-Salzburg UsingRecycling and the ExposedAggregate Technique,” TechnicalReport, Cement ResearchInstitute, Vienna, Austria, 1992.

Breyer, G. “Low-Noise RoadSurfaces in Austria,”Proceedings: International Tire-Road Noise Conference,Gothenburg, Sweden, 1990.

“Quiet Concrete,” WorldHighways magazine, May/ June1992.

Sommer, H., “Noise ReducingConcrete Surfaces - State of theArt 1992,” Results of a PIARC-Workshop held in Vienna 24-25February 1992.