1

Program Background and Introduction to Specifications

9th Annual Meeting - Construction of Crack-Free

Concrete Bridge Decks July 19, 2011

Kansas City, MO

OutlineOverview of LC-HPCSpecifications and their applicationWhere we stand

Scope of Work

Low-Cracking High Performance Concrete (LC-HPC) Bridge Decks

23 LC-HPC decks (28 placements) ( p )completed through 2010

1 LC-HPC deck to be constructed this year

More to be let in MN

Bridges

Primarily composite steel girder bridges

Full-depth slabsRemovable formsMatching bridges to serve as a control where possible (Phase I)

Why LC-HPC?

Cracks

Why LC-HPC?

Negative impact of cracks on concrete in the decks.

Negative impact of cracks on corrosionNegative impact of cracks on corrosion performance of both conventional and epoxy-coated reinforcement.

2

Our goalEliminate cracking in bridge decks

To do this, we need to minimize cracking due tocracking due to

Plastic shrinkageSettlement over reinforcing barsThermal contractionDrying shrinkage

Factors that affect crackingAgeDeck typeCement paste contentCompressive strengthAir contentAir contentSlumpTemperatureConstruction dateCuringConstruction techniques

Age

0.60

0.80

1.00

1.20

ensi

ty, m

/m2

Monolithic

0.00

0.20

0.40

0 25 50 75 100 125 150 175 200 225 250 275

Cra

ck D

e

Bridge Age, months

Bridge Deck Type

0.51 0.490.44

0.33

0 200.300.400.500.600.700.800.90

ck D

ensi

ty, m

/m2

Age

Cor

rect

ed

0.000.100.20

7% SFO 5% SFO CO MONO

Bridge Deck Type

Cra

Number of Bridges

(9) (18) (30) (16)

Number of Surveys

(9) (36) (52) (32)

Paste Content

0.19 0.16

0.680.73

0.200.300.400.500.600.700.800.90

ack

Den

sity

, m/m

2

Age

Cor

rect

ed

0.000.10

26 27 28 29

Percent Volume of Water and Cement, %

Cra

Number of Placements

Number of Surveys

(8) (16) (4) (5)

(16) (31) (8) (11)

Monolithic

0.18

0.31

0.51

0.87

0 150.19 0.22

0 200.300.400.500.600.700.800.90

ack

Den

sity

, m/m

2

Age

Cor

rect

ed

Uncorrected

Adjusted for Water Content

Slump

0.11 0.15

0.000.100.20

38 (1.5) 51 (2.0) 64 (2.5) 76 (3.0)

Slump, mm (in.)

Cra

Number of Placements

Number of Surveys

(5) (20) (5) (1)

(10) (40) (11) (3)

Monolithic

3

Compressive Strength

0.160.26

0.49

0 200.300.400.500.600.700.800.90

ack

Den

sity

, m/m

2

Age

Cor

rect

ed

0.000.100.20

31 (4500) 38 (5500) 45 (6500)

Compressive Strength, MPa (psi)

Cra

Number of Placements

Number of Surveys

(7) (12) (10)

(13) (24) (23)

Monolithic

0.37 0.38

0.300.400.500.600.700.800.90

ck D

ensi

ty, m

/m2

Age

Cor

rect

ed

Air Content

0.13

0.000.100.20

4.5 5.5 6.5

Air Content, %

Cra

c

Number of Placements

Number of Surveys

(7) (19) (5)

(14) (40) (10)

Monolithic

0.19

0.330.37

0.44

0 20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

ack

Den

sity

, m/m

2

Age

Cor

rect

ed

High Air Temperature

0.00

0.10

0.20

5 (41) 15 (59) 25 (77) 35 (95)

High Air Temperature, C (F)

Cra

Number of Placements

Number of Surveys

(4) (15) (9) (4)

(8) (31) (17) (9)

Monolithic

0.50

0.300.400.500.600.700.800.90

ck D

ensi

ty, m

/m2

Age

-Cor

rect

ed

Date of Construction - Monolithic

0.16

0.000.100.20

1984-1987 1990-1993

Date of Construction

Cra

c

Number of Bridges

(6) (7)

Number of Surveys

(12) (16)

0.24

0.53

0.81

0.300.400.500.600.700.800.90

ack

Den

sity

, m/m

2

Age

Cor

rect

ed

Date of Construction - Conventional Overlays

0.000.100.20

1985-1987 1990-1992 1993-1995

Date of Construction

Cra

(6) (36) (6)

(6) (17) (3)Number of BridgesNumber of Surveys

4

0.87

0.55

0.420.48

0.300.400.500.600.700.800.90

ck D

ensi

ty, m

/m2

Age

Cor

rect

ed

Date of Construction - Silica Fume Overlays

0.000.100.20

1990-1991 1995-1996 1997-1998 2000-2002

Date of Construction

Cra

c

(6) (20) (16) (10)

(2) (10) (8) (10)Number of BridgesNumber of Surveys

Control of early evaporation and improved curing

0.87

0.58 0.61

0.390.48

0 300.400.500.600.700.800.90

kD

ensi

ty, m

/m2

Age

Cor

rect

ed

Control of early evaporation and improved curing -Silica Fume Overlays

0.000.100.200.30

NONE R1, R2 R3 R4, R5, R6 R8, R9

Special Provision, (R#)

Cra

ck

Ag

(6) (8) (10) (18) (10)

(2) (4) (5) (9) (10)Number of BridgesNumber of Surveys

4

5

6

7lu

mp,

in.

MONO

CO Subdecks

5% SFO Subdecks

7% SFO Subdecks

1

2

3

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004

Sl

Placement Date

5

6

7

8

9

10

ump,

in.

MONO

CO Subdecks

5% SFO Subdecks

7% SFO Subdecks

1

2

3

4

1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Slu

Placement Date

Overall ApproachWork to reduce plastic, settlement, thermal

and drying shrinkage cracking

Low cement & water contentsLow slumpLow slumpHigh strength is not goodLow evaporation rateConstruction methods and materials matterMore early cracking means more total

cracking

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LC-HPC SpecificationsOptimized Aggregate GradationLow-absorption Aggregate1 inch Max Size AggregateCement Content ≤ 540 lb/yd3

w/c ratio = 0.43 – 0.45Air Content of 8 ±1½%Designated slump 1½ – 3 in. (4 3½ in. max)Controlled temperatureImproved curing

Concrete temperature control

55 – 70°F 50 – 75°F if approved by Engineer pp y g

Cold-weather concreting

Maintain temperature of both girders and deck.

Alternatives to Pumping

Concrete BucketsConveyor Belts

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Placing

Air cuff/bladder valve on pump or limit drop with conveyorFilling end walls and diaphragms ahead of slab

Consolidation RequirementsVertically mounted internal gang vibrators

Concrete Finishing

General Rule:Less is More

Pan or burlap dragBullfloating only if neededneededWater is not a finishing aid!

Curing

Presoaked burlapTimely placementConstantly wetConstantly wet

Spray hosesSoaker hoses14 days

Three work bridges. Four rolls of pre-cut, pre-soaked burlap, two on each side

Cost effectivenessCost of equipment: approximately $5000Cuts work crew to handle burlap on day of placement from 11 to 5 Contractor added power to move the work bridges between first and second deck

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Curing

Followed by curing compound to slow the rate of evaporation

Qualification Batch & Slab

Construction Schedule

Bridge Construction

Concrete Testing & Acceptance

Clearly define testing schedule ahead of timeC i tCommunicate how out-of-spec concrete will be handled

Specifications

07-PS0167 Construction07-PS0166 Concrete07 PS0165 Aggregates07-PS0165 Aggregates

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Where we standLC-HPC decks are workingCurrent provisions, however, don’t encompass all of the technologies that can be brought to barecan be brought to bareWe chose not to propose those technologies until we were assured that they posed no durability problems

We’ve now evaluated those technologies for durability and are prepared to recommend their adoptionReady for some more decks!

This year’s crack surveysAdherence to the rules...

Questions

The University of Kansas

David Darwin, Ph.D., P.E.Deane E. Ackers Distinguished Professor Director, Structural Engineering & Materials Laboratory

Dept. of Civil, Environmental & Architectural Engineering2142 Learned HallLawrence, Kansas, 66045-7609(785) 864-3827 Fax: (785) 864-5631

daved@ku.edu

The University of Kansas

JoAnn Browning, Ph.D., P.E.Professor

Dept. of Civil, Environmental & Architectural Engineering2142 Learned HallLawrence, Kansas, 66045-7609(785) 864-3723 Fax: (785) 864-5631

jpbrown@ku.edu