Building Bridgesand Marine Structures

With Structural LightweightAggregate Concrete

For Further Informationabout LWA and

Producers/Suppliersin Your Area,

ContactExpanded Shale,

Clay and Slate Institute801-272-7070

or visit uswww.escsi.orginfo@escsi.org

Publication No. 4700 • February 2001

Photography Credits: Coronado Bridge © 1992 Steven Simpson, Inc. San Diego, CAWilliam Preston Lane Bridge © 1991 Tadder, Baltimore, MD

Printed In U.S.A.

Why Use StructuralLightweightConcrete (SLC)In BridgeConstruction?

1. Lower Weight∆ Structural Lightweight

Concrete is typically25% to 30% lighter.

∆ Requires less reinforcing,prestressing andstructural steel.

∆ Increases live loadcapacity

∆ Permits longer spans.∆ Permits deeper

sections withoutincreasingdead load.

∆ Allows for bridge upgrades andexpansion withoutreplacing or addingsupport foundations.

∆ Reduces seismic forces.

2. High Durability∆ Low permeability.∆ High resistance to

freezing and thawing∆ Good resistance to

deicing salts andchemicals.

∆ The close elasticcompatibility betweenthe aggregate and the mortar fractionreduces internal stresses and also minimizes microcracking.

∆ Superior bond and transition zone between the aggregateand cement paste.

∆ Non-polishing and ahigher skid resistantsurface improvesroadway safety.

Benicia-MartinezBridgeHwy. 680 between thecities of Benicia andMartinez, California Beginning: 2001

Silver Creek OverpassOver I-80, Summit County, Utah

Completed in 1968Bridge Length:

191 feet, 9 inchesMaximum Span: 99 feet, 9 inches

Bridge Width: 44 feetEngineer: Utah Department of

Transportation StructuresDivision

Highway expansion in 2001resulted in removal of this

structure. Examination of theSLC after 33 years in use

showed little or no deterioration.

Cooper River BridgeCharleston, South Carolina

Shown under construction in 1991Bridge Length:

16,450 feetBridge Width:

93 feet, 3 inchesEngineer:

Howard-Needles-Tammen & Bergendoff

On The CoverCoronado Bridge

San Diego, CaliforniaInset Cover Photos

• Boknasundet BridgeUnder ConstructionRogaland County, Norway (Left)

• Pontoon Supports for Nord Hordland Floating BridgeBergen, Norway (Middle)

• Hibernia Offshore PlatformNewfoundland, Canada (Right)

Bridge Type: 5-lanebalanced pre-stressedCIP segmentalcantilever sandlightweight concretebox girder with room for light rail on west side.Built with SLC, steel hinges, and deep foundations to help withstand 1,000-2,000 year-return earthquake.Maximum Span: 200 m. Typical Span: 161 m. Total Length: 2,716 m.SLC: 6,500 psi at 28 days. Owner: State of California, Caltrans.Design: T.Y. Lin International and CH2M HILL

Existing Benicia-Martinez Bridge

Existing Railroad Bridge

New Benicia-Martinez Bridge

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The Test of Time

For more than 80 years structural lightweight aggregateconcrete (SLC) has solved theweight and durability problemsassociated with exposedstructures. This concrete, madewith rotary kiln expanded shale,clay or slate (ESCS) lightweightaggregate, has a provenperformance history in bridgesand other marine structures.Examination of the structures hasconfirmed that, in terms of durabil-ity, structural lightweight concreteperforms equal to or better thannormal weight concrete.

In the study “Criteria ForDesigning Lightweight ConcreteBridges” (August 1985) theFederal Highway Administrationreports that evidence was produced during visits to 30bridges, and in contacts with stateand industry representatives, thatgood lightweight concrete hasequal or better durability thansome normal weight concrete.

In 1975 an independent study of the Lane Bridge acrossthe Chesapeake Bay concluded that “concrete containing porouslightweight aggregate is less susceptible to deterioration fromfreezing and thawing” than normal weight concrete.

A survey of Japanese bridges in service for up to 20years reveals that cracking,carbonation and salt penetrationwas reduced with structural lightweight concrete bridges, and SLC provided high degrees of durability that surpassed normalweight concrete. Also, investiga-tions of a number of older marineenvironment SLC structures inservice for over 80 years verifylaboratory results indicating goodweathering resistance.

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Why Use StructuralLightweightConcrete (SLC)In BridgeConstruction?

3. Low Cost∆ Provides versatility

for renovation andretrofitting. Deckscan be widened or replaced without altering existing support system.

∆ Reduced cost oftransportation anderection are realizedwith precast mem-bers. More precastmembers can betransported per truck and less cranecapacity is required.

∆ Lower foundationcosts result fromreduced size and/ornumber of supports.

∆ Lower constructioncosts result from reduced need for extensive falsework/formwork, lessreinforcing steel, andsmaller structuralmembers.

∆ Greater design flexi-bility to meet today’schallenges of designand construction.

∆ High compressivestrengths capable ofmeeting modern engineeringrequirements.

Boknasundet BridgeRogaland County, Norway

Bridge Type:Balanced cantilever

Length:1270 feet (385 meters)

Maximum span627 feet (190 meters)

Bridge Width:36 feet, 4 inches (11 meters)

Engineer:Bridge Department

Director of Public Works

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William Preston Lane BridgeChesapeake Bay at Annapolis, MarylandDeck replacement.Engineer: Greiner EngineeringNote: SLC bridge decks constructed in 1952 demonstrated superiorperformance when compared to companion heavyweight concretedecks; therefore, SLC bridge decks were chosen by the ownersand engineers for the parallelspan opened in 1975.

Heart of America BridgeKansas City, Missouri

Completed in 1985Composite deck, SLC cast-in-place

topping over precast SLC panels.Maximum Span: 440 feet

Engineer: Howard-Needles-Tammen & Bergendoff

Neuse River BridgeU.S. 17 at New Bern, North Carolina

Conventional design using SLC decks onnormal weight AASHTO beams.

Elevated interchanges were required becauseof sensitive wetlands (north) and

historic district (south)Engineer: Ralph Whitehead Engineers

Owner: NCDOT

Ohio Turnpike Twin BridgesMaumee River, Toledo, OhioDeck replacement and widening.Bridge Length: 1384 feetMaximum Span: 176 feet, 6 inches (longest)11 spans (composite with post-tension SLC)Engineer: J.E. Greiner Company

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Why Use StructuralLightweightConcrete (SLC)In BridgeConstruction?

4. Excellent PerformanceRecord

∆ Structural LightweightConcrete has a proven performance ofsuccessful use inseverely exposedmarine and bridgeconstruction formore than 80 years.Over this periodit has been subjectedto extreme weatherand loading conditions, and hasproven soundand durable.

Sandhornøya BridgeGiddenskill, Nordland County, Norway

Completed in1989Bridge Type: Balanced cantilever box girder

Total Length: 1234 feet, 2.4 inches (374 meters)Maximum Span: 508 feet, 2.4 inches (154 meters)

Bridge Width: 25 feet, 9 inches (7.8 meters)Engineer: Aas Jakobsen, Oslo

Sabestian Inlet BridgeVero Beach, FloridaCompleted in 1964. 1991 review showedSLC deck to be in good condition. Precast and prestressed girder system with cast-in-place deck.Maximum Span: 180 feet

Raftsundet BridgeRaftsundet Sound, Norway

Located over 300 kilometers north of the Arctic Circle.Bridge Type: Continuous post-tensioned,

cast-in-place, box section. Central 224 meters of the298 meter main span is constructed of high performance

structural lightweight concrete.Engineer: Dr. Ing Aas-Jakobsen

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LightweightAggregateConcrete InNorwegian Bridges

“To help bridgedesigners in their effortsto create optimum struc-tures, the Norwegianconcrete industry, in the 1980’s, started to

(Continued on page 11)

by Steinar Helland, SelmerSkanska AS, Oslo, Norway.

LewistonPump-Generating

Plant BridgeLewiston, New York

204 prestressed SLC girders of 68 feet each.6000 precast SLC roadway slabs (4000 psi)

3 inches thick (7 feet x 2 feet each)24 special walkway girders (“U” shaped,

6 feet wide and 4 feet deep).Engineer: Uhl, Hall & Rich

Antioch BridgeAntioch, California

Completed in 1972.2-lane SLC deck

placed by pumping.Bridge Type:

Prestressed concrete multiple box.

Why so Durable?Resistance to freezing and thawing in any type of

concrete (normal weight or lightweight) is achieved by usingdurable aggregates encased in a durable cement mortar.Although expanded shale, clay and slate (ESCS) aggregatesare absorptive, they are also very durable, being composedof vitrified silicates. Laboratory tests showing high DurabilityFactors after 300 cycles of freezing and thawing are normalfor structural lightweight aggregate concrete. It is no surpriseproperly proportioned air entrained SLC made with ESCSlightweight aggregate is quite durable.

In addition to being durable, ESCS aggregates have otherunique properties that lead to increased durability. Theseproperties include better elastic compatibility, internal curingand improved bond between the lightweight aggregate andthe cement paste.

ESCS aggregates are less rigid than normal weightaggregates. Moreover, their stiffness closely matches that ofthe air entrained mortar fraction used in bridge deck concrete.Studies show that this elastic compatibility results in signifi-cantly lower stress concentrations at the aggregate-pasteinterface and greatly reduces the tendency for microcracking.

The contact zone is the transition layer connecting thecoarse aggregate particle and the enveloping cement mortar.The quality of this interface is a decisive factor in the long-term durability of concrete. Several studies have shown thatthe contact zone in lightweight aggregate concrete is farsuperior to that of normal weight concrete. Consequently thelightweight aggregate bond to the mortar matrix exceeds thebond of normal weight aggregate.

The water absorbed in lightweight aggregate providesavailable moisture for enhanced cement hydration. Thewater does not affect the water-cement ratio. The enhancedcement hydration results in improved durability, less micro-cracking and lower permeability.

Prestressed, Precast and Cast-In-PlaceStructural Lightweight Concrete is ideal for all types of

bridge or other marine construction. The lower weight makesit economical to transport sizeable precast sections, reducesthe need for extensive falsework, speeds erection and allowsfor the use of smaller more economical equipment.

The overall weight reduction with SLC affords designersgreater design latitudes to meet today’s challenges of terrain,budget, seismic conditions and construction schedules. Inaddition, reduced weight produces less seismic force, andallows for reduction of reinforcing and structural steel, smallerfoundations and longer spans. The result is a substantialcost savings.

Structural lightweight concrete also allows the deck thickness to be increased without increasing overall weight,as compared to normal weight concrete. This affordsincreased stiffness and additional cover for reinforcing, thereby improving durability.

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Coronado BridgeSan Diego, California307 precast-prestressedSLC girders were used.Completion: 1969Bridge Length: 11,179 feetBridge Height: 50 to 200 feetMaximum Girder Length: 151 feetEngineer:State of CaliforniaDepartment of Public Works,Division of Bay Toll CrossingsE.R. Foley, Chief Engineer

American River BridgeCity of Folsom, California • Completion: 1999Bridge Type: 4-lane prestressed concrete box girder road with a 6.1 m median for future light rail. Span: Maximum of 100 m • Total Length: 690 mSLC Concrete: 5,000 psi at 28 daysOwner: City of Folsom, California • Design: HDR Engineering Construction: C.C. Myers, Inc. • Ready Mix: RMC Lonestar

8th Street BridgeSheboygan, WisconsinFirst bascule bridge in the world with reinforced concrete deck. This single-leaf, unbalanced bascule bridge consists of a 6-inch SLC deck carried by apair of longitudinal steel girders interconnected at the pivot end by circularcross girders. There is no counterweight. Hydraulic power lifts and lowers the bridge.Bascule Span: 81 feet. Bridge Width: 75 feet.Owner: State of Wisconsin/City of SheboyganEngineer: Teng and Associates, Inc., Chicago, Ill.Concrete Supplier: Sheboygan Concrete

Brooklyn BridgeNew York, New York

Emergency re-deckingCompletion: October 1999.

Steel grid filled with 6000 cubic yards of SLC (4000 psi)

Owner:New York City DOT

Contractor:Yonkers Construction

Concrete Supplier: Rahns Concrete

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Napa BridgeHwy. 29 at Napa River, Napa, CaliforniaCompleted: 1977Type: 4-lane prestressed concrete box Typical Span: 250 feetTotal Length: 2,230 feetSLC Strength: 4,500 psi at 28 daysOwner: State of CaliforniaDesign: Caltrans

Braddock Gated DamBraddock, Pennsylvania

SLC Construction Begun: March 2000 Precast and cast-in-place elements are being used

to construct dam sections up river. SLC is used in the interior dam support walls and

floor sections to reduce weight and draft of the floatable sections. Maximum draft will be

10-14 feet. Sections will be floated down river and set in place on a pier foundation

system. Additional precast and cast-in-place construction will accommodate lock gates,

control facilities and a pedestrian bridge.Wier bay sections: 110 feet

Dam Section 1: 333 ft. • Dam Section 2: 265 ft.Contractor: J.A. Jones/Traylor Brothers

Owner: Army Corps of Engineers

Longest Prestressed Post-tensioned GirderLafayette, Indiana Production Date: 1994Producer: Hydro Conduit/LafayetteGirder Type: Prestressed post-tensioned bulb teeQuantity: 96 GirdersLength: 175 feet • Height: 7.5 feetWeight: 96 tons • 5-Day Strength: 7,000 psi Design: High strength specified density concretein combination with pre-stressed/post-tensionedstrand. Weight was reduced by 17%.Cost: The contractor chose the prestress con-crete design over the steel design and saved $1.7million on the $9.4 million Wabash River Bridgeproject. (Bridge pictured on bottom right page)

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Renovation & RepairIn 1990 more than one-half

million bridges in the UnitedStates alone were classified as“deficient” in terms of structuralintegrity or traffic capacity. Thisstaggering need for renovation,repair or replacement can belargely addressed with the useof Structural LightweightConcrete (SLC).

One of the most extensiveapplications of SLC can beseen in bridge re-decking.SLC decking achieves two significant goals: low deadloadand high durability. The combi-nation of these two factorsoften means that bridge widths,traffic lanes, and the thicknessof structural slabs can beincreased while utilizing exist-ing piers, footings and otherstructural members. Dependingon the nature of the renovation,the use of SLC often increasesthe live load capacity for olderbridge structures, thus meetingthe current load specifications.

The use of SLC in bridgestructures constitutes a power-ful renovation tool. This lighter,more durable material helpsdesigners by providing designsolutions for bridge structuresthat adequately address bothexpansion and economicissues.

For more informationon the advantages of

lightweight concrete madewith expanded shale, clay or

slate, contact your local supplier of rotary kiln

expanded shale, clay or slatelightweight aggregate.

www.escsi.org

BraddockGated DamFloatable sectionunder construction(February 2001)

Cast-in-placeSLC interior supports and floor sections

Wabash River Bridge, 231 Bypass Lafayette, IndianaOwner: State of Indiana • Design: Jansen & Spaans EngineeringContractor: Rieth-Riley Construction Company(Girder photo and information shown on left page)

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BraddockGated DamFloatablesection to be set in place on pierfoundation

Marine StructuresMarine Structures

CIDS Island Drilling SystemCanadian Beaufort SeaBuilt in Japan in 1984, the use of HSLDC reduced draft during construction and towing, improvedfloating stability, and improvedtopside loads. Much of the intermediate level of the structurewas constructed with HSLDC.Compressive strength was 45 MPa(6,500 psi), and the density was1,840 kg/m3 (115 lb/ft3).

Tarsuit Caisson Retained IslandCanadian Beaufort SeaBuilt in 1981, this is the first Arcticstructure using SLC. Four prestressedconcrete caissons, 69x15x11 meters high(226x50x35 ft.), were built in Vancouver,towed around Alaska, and founded on adredged sand berm 40 km (25 miles) off-shore in the shear zone between winterlandfast ice and moving Arctic ice. Spacebetween the caissons was filled withdredged sand to form the working platformfor the drill rig.

combine the technology ofHSC/HPC with that of lightweightaggregate concrete (LWAC). Tenmajor bridges were built with light-weight concrete in Norway. Thesecomprised free cantilever, cablestayed, and pontoon bridges. Thespans of the two latest free can-tilever bridges – Raftsundet at 978ft (298 m) and Stolma at 988 ft.(301 m) – represent world records.”(S. Rosseland et al)

The motivation for using LWACfor free cantilevers is the effect ofreduced dead load. Additionally,the construction method requires abalanced load on both sides of thepylon during construction. Thislimits the choice of span lengthsand the possibility of placing pylonsaccording to the topography. Bybeing able to adjust the materialdensity of the cantilevers, thedesigner achieves greater freedom.

Over the last 15 years, extensiveresearch in Norway has verifiedLWAC’s performance in marineenvironments. Test results showthat LWAC will withstand a structur-al design life of more than 100years with comfortable margins.Conclusion

“To maintain the use of concretein bridge construction, the range ofmaterial combinations had to bebroadened in the 1970’s and 80’s.The introduction of higher strengthsand better performance in marineand de-icing salt environments wasthe first step. The second step wasto give designers the possibility ofcombining these characteristics withthe freedom to specify density.Without these quantum leaps intechnology, concrete’s leading position in this market would havebeen questionable.” (Steinar Helland)

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(Continued from page 5, LWAC In Norwegian Bridges)

The above is excerpted from an article in HPCBridge Views, Issue No. 11, published by theFederal Highway Administration and the NationalConcrete Bridge Council. Sept./Oct. 2000

Hibernia Offshore PlatformNewfoundland, CanadaTo improve the buoyancy of the largest floating structure everbuilt in North America, structural lightweight aggregatereplaced approximately 50% of the coarse aggregate fractionof the High Strength Specified Density Concrete used in theHibernia Gravity Base Structure. This structure, with a massof more than one million tons, was successfully floated out ofthe drydock, and towed to a deep water harbor area whereconstruction continued. It was then towed to the Hibernia OilField site, 200 miles (315 Km) east-southeast of St. John’s,Newfoundland, and set in place on the ocean floor. (see cut-away view at right)

North America’s largest floating structureNorth America’s largest floating structure

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Heidron FloatingConcrete Offshore

PlatformNorth Sea, Norway

The Heidron oil fields lie345 m (1,130 ft.) below thecold stormy surface of the

North Sea. Because ofthe need to achieve

the required buoyancy,the concept of using

high-strength low density concrete (HSLDC) wasintroduced early in the

planning stages.The hull of the floating

structure is constructedentirely of HSLDC

(60 MPa / 8,700 psi cubestrength). Almost

70,000 m3 (91,000 yd3) ofHSLDC with a maximum

density of 2,000 kg/m3

(125 lb/ft3) and a requiredelastic modulus of

22 GPa (3.19 x 106 psi)were used.

The first floating platform with HSLDCThe first floating platform with HSLDC

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Powell River ShipsPowell River, British Columbia, Canada

Floating SLC VesselsFloating SLC Vessels

Powell River ShipsCore SampleDrilled core samples revealedthat the SLC of the ship’s hullhad continued to mature andstrengthen well beyond itsdesign strength.

Ten concrete ships are being used asa floating breakwater at the PacificPaper Powell River Plant. Evaluation of the ships for long-term service durability of the lightweight concretewere recently conducted. The shipsrange in age from 55 to 80 years, withone ship constructed in the 1920’s,and the other nine in the 1940’s.These ships demonstrate the excellentperformance of structural lightweightconcrete after more than a half-centuryof marine exposure.

Petrographic studies conducted atCTL (Construction TechnologyLaboratory) revealed limited microc-racking, excellent aggregate/matrixcontact zone, complete hydration of thecement, and insignificant damage dueto freezing and thawing. This micro-scopic examination clearly showed evidence of continued hydration anddevelopment of the cement matrix. Thiscontinued maturation of the concretehas contributed to the development ofcompressive strengths in the ships’hulls well beyond (up to 8700 psi) theminimum design strength (5000 psi) ofthe concrete. Concrete densities rangefrom 106 lb/ft3 to 130 lb/ft3 .

According to the inspectors’ report,the “paste-aggregate bond is consis-tently excellent in all the examined con-crete specimens, in part attributed tomostly beneficial reactions along thepaste-aggregate interface. Overall, themanufactured lightweight concrete usedin the construction of the ships has per-formed exceptionally well in a harshmarine environment.”Text taken from the ACI publication,

SP 189-7, “Evaluation of Lightweight

Concrete Performance in 55 to 80 Year-

Old Ships,” by R.D. Sturm, N. McAskill,

R.G. Burg and D.R. Morgan

Paste-AggregateInterfaceScanning electronmicroscopephotograph of aggregate/matrixcontact zone; from thecover of “State-of -the-Art Report on High-Strength, High-Durability StructuralLow-Density Concretefor Applications inSevere MarineEnvironments” byThomas A. Holm andTheodore W. Bremmer

Innovations For Navigation Projects Research ProgramUS Army Corps of Engineers Research and Development Center

Note: Additional information on the properties and performance of lightweight concrete can be obtainedby viewing the referenced publication by Holm and Bremmer on the Army Corps of Engineers web site“Reports Page” – (http://www.wes.army.mil/SL/INP/reports.htm)

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