2B MassConc Chin Cote Ague Celik

8/6/2019 2B MassConc Chin Cote Ague Celik

1/39

A partnership of the V i rg i n i a Depar tm en t o f T ranspor t a t i on and the Univers i t y o f V i rg in ia since 1948

Virginias Mass Concrete Experiences:

Requirements for a Good Specification

Celik Ozyildirim, PhD, PEVTRC, VDOT

2009 Virginia Concrete Conference


2/39

03/05/2009

Outline

Mass Concrete Temperature Measurement

Testing for strength

Field Applications Bridge on I-895 over James River

Route 33 Bridges at West Point

Bridge at Chincoteague

Specifications


3/39

03/05/2009

Mass Concrete

Any volume of concrete withdimensions large enough to requirethat measures be taken to cope with

generation of heat from hydration of thecement and attendant volume changeto minimize cracking.

Ref: ACI 116R-00


4/39

03/05/2009

Problem Heat is generated during hydration

Temperature differences occur between the interior andthe exterior surface Significant thermal stresses occur due to restraint Moisture differences contribute to stresses

Cracks occur when stresses exceed the strength of theconcrete Cracks adversely affect durability and structural integrity

At later ages delayed ettringite formation occurs wheninitial temperature exceeds 70 C (158 F). Can bemitigated with pozzolans.


5/39

03/05/2009

Temperature Prediction

Maximum Temp = Initial concrete Temperature

plus adiabatic temperature rise (heat energywhen no loss occurs) minus heat loss to thesurrounding

Simplistic Method (for placements > 6 ft thick)ignores heat loss

Refined method: finite element modeling includes

control measures (such as cooling, insulation)and the environment


6/39

03/05/2009

Reducing Thermal Issues

Use a mixture with reduced heat: low amountof cementitious material

Limit the maximum temperature: mixture

design, precooling concrete, internal coolingpipes

Limit the temperature difference: curing,

insulation

ACI 207, 224, 301


7/39

03/05/2009

Mass Concrete

Specifications

Limits on placement temperature

Maximum temperature, and

maximum difference in temperaturebetween interior and surfaceconcrete

are commonly used in an attempt tominimize cracking of massivesections


8/39

03/05/2009

FLDOT Mass Concrete

Minimum dimension > 36 in

Volume to surface area > 12 in Drilled shafts diameter > 72 in

Temperature difference < 35 F (at higher difference

potentially damaging cracks are likely to form) Maximum initial concrete temperature is 85 F unless

precautions are taken (then 100 F)

Class F fly ash 35 to 50% and slag 50 to 70 % if core

temp >165 F


9/39

03/05/2009

TXDOT Mass Concrete

Least dimension: 5 ft Max temperature: 160 F

Max temperature difference 35 F

Initial maximum temperature 75 F Class F fly ash up to 45 %

ConcreteWorks computer program


10/39

03/05/2009

VDOT Mass Concrete

Max temp 160 F (if slag concrete 170 F) Max temp difference 35 F

Class F fly ash 25 to 40 %

Slag 50 to 75% Max initial concrete temperature 95 F

Thermocouples to be cast in-line vertically in the

structure to measure the thermal gradientbetween the core and the surface


11/39

03/05/2009

Strength Measurement

Maturity:

Maturity index, time-temperature factorArrhenius equation, equivalent age

Temperature-matched curing


12/39

03/05/2009

Mass ConcreteI-895 over the James River


13/39

03/05/2009

I-895

Large footings (35 x 40 x 10 ft)

High temperature development

Slag used as 75% of cementitiousmaterial to control temperature


14/39

03/05/2009

I-895 Footing

pc=142 lb/yd3

Slag=423 lb/yd3

75% slag

Max w/cm = 0.4930 MPa (4350 psi)


15/39

03/05/2009

Temperature Data

40

60

80

100

120

140

160

180

200

7/28/01 8/2/01 8/7/01 8/12/01 8/17/01

Date

Temperature(F)

Middle

Top

Ambient Air


16/39

03/05/2009

I-895 Compressive Strength

(psi)

DateDate

0

1000

2000

30004000

5000

60007000

2/25 4/1 4/15 6/17 7/1 7/29

Top (7d)

Top (28d)Center (7d)

Center (28d)


17/39

03/05/2009

PERMEABILITY

561 coulombs

840 coulombs


18/39

03/05/2009

Footings, Columns, Beams


19/39


20/39

03/05/2009

Footing versus Beam


21/39

03/05/2009

Route 33 Bridges


22/39

03/05/2009

Route 33 Pier Caps

pc=353 lb/yd3

Class F flyash=235 lb/yd3

40% fly ash

Max w/cm =0.46

A3: 3000 psi

Column caps 6x6 and 6X6.5 ft


23/39

03/05/2009

Mattaponi Bridge, Pier Cap 12

0

20

40

60

80

100

120

1/20 1/22 1/24 1/26 1/28 1/30 2/1

Date, 2005

Temp

erature(F)

Air Temp

Center Temp

Bottom Temp

Top Temp

Temp Difference


24/39

03/05/2009

Pamunkey Bridge, Pier Cap 47

0

20

40

60

80

100

120

140

160

8/16 8/16 8/17 8/17 8/18 8/18 8/19 8/19

Date, 2005

Tempe

rature(F)

Air Temp

Center Temp

Bottom Temp

Top Temp

Temp Difference


25/39

03/05/2009

Strength and PermeabilityFooting, Pier, Cap

199132202132Number

928180450735420Maximum

8321027932770Minimum

144264495467Std Dev

36944939593732AveragePamunkeyMattaponiPamunkeyMattaponi

Permeability (coulomb)Strength (psi)

Values


26/39

03/05/2009

Chincoteague Bridge

On Route 175 over Black Narrows and Lewis

Creek Channel. The large bascule footing wasplaced in 2008.

Change in the concrete class in bascule footing

to A3 and need for mass concrete specification Contractor requested twice the cost of concrete

for a thermal analysis and thermal monitoring


27/39

03/05/2009

Bascule Footing

110 tons of steel110 tons of steel


28/39

03/05/2009

Thermal Control Plan A thermal analysis model used by the cement producer to

estimate the temperature difference for potential cracking. Low-heat concrete mixture using 539 lb/yd3 cementitious

material with 30% fly ash. Regular A3 has a minimumcementitious content of 588 lb/yd3.

Heavy reinforcement to control cracking

Water curing and insulation

Time of placement; late May before the hot weather

VTRC/VDOT to monitor the temperatures


29/39

03/05/2009

Mixture Proportions,

Strength and Permeability

Bascule Footing

pc=378 lb/yd3

Class F fly ash=161 lb/yd3

Water=246 lb/yd3

Max w/cm=0.46

Samples n=13, str=avg of 3; perm= 1

Strength: avg=5114 psi; stdev=420 psi Perm: avg=373 coulombs; stdev=79 coulombs


30/39

03/05/2009

Bascule Footing

77--ft deepft deep


31/39

03/05/2009

Chincoteague FootingMaximum and Differential Temperature

0

20

40

60

80

100

120

140

160

5/28 5/30 6/1 6/3 6/5 6/7

Date, 2008

Tempe

rature(F)

Air

NT

NM

NBN (M-T)

N (M-B)


32/39

03/05/2009

Chincoteague FootingTemperature Difference

0

10

2030

40

50

60

70

80

5/26 5/28 5/30 6/1 6/3 6/5 6/7 6/9 6/11

Date, 2008

Temperature(F)

NM-CB

NM-CM

NM-CT


33/39

03/05/2009

Edges and CornersACI 207.4R:

Tensile strains develop more quickly at edges andcorners than on the sides or tops of the structure.Increased insulation along the edges and at cornershelps.

The development of steep thermal gradients nearexposed surfaces during early ages while the modulus ofelasticity is very low is usually not a serious condition.


34/39

03/05/2009

Specs

Measure temperature in massconcrete at the core and surfacealong a vertical direction and at thecorners

Base strength on maturity ortemperature matched curespecimens (at least 7 daystemperature matching)


35/39

03/05/2009

Specs

Any placement of structural concrete with aminimum dimension greater than 3 ft. Smallerdimensions should be considered if Type IIIcement or accelerators or cementitiousmaterial exceeding 600 lb/yd3 is used.

Drilled shafts with a minimum diameter of 4 ft.


36/39

03/05/2009

Specs

Prescriptive approach

Limit initial concrete temperature to 85F

Limit maximum temperature to 160 F,unless 40-50% Class F fly ash or 60-75%slag is used; then the maximum

temperature may be 170 F. Temperature differential shall be (35 F)

Require controls on mixture proportions:maximum cementitious material shall be

600 lb/yd3, and minimum fly ash 25% andminimum slag 50%, specify maximumw/cm, provide insulation


37/39

03/05/2009

Specs

ERS approach

Contractor/producer designs themixture and

Provides information on trialbatching or historic data

accompanied by thermal modelingto show that the mixture canproduce satisfactory strengths andcontrol cracking (no or limited

cracking) for the given structure in agiven environment.


38/39


39/39

03/05/2009

Questions?

2B MassConc Chin Cote Ague Celik

Documents

Transcript of 2B MassConc Chin Cote Ague Celik