juenger - thermal cracking

Maria Juenger

The University

of Texas at

Austin

SUPPLEMENTARY

CEMENTITIOUS MATERIALS

AND OTHER

THERMAL CONTROL

STRATEGIES FOR CONCRETE

MODERN CONCRETE

Cement

Water

AirSand

Stone/gravel

eatandys.com

ACI Concrete Terminology definition of SCMs:Inorganic material such as fly ash, silica fume, metakaolin, or ground-

granulated blast-furnace slag that reacts pozzolanically or hydraulically

� Waste

� fly ash

� ground granulated blast

furnace slag

� silica fume

� Natural

� volcanic (glassy)

� tuff (zeolitic)

� sediments (rich in siliceous diatoms)

� diagenic (rich in amorphous silica)

� Processed Natural

� crushed bricks or clay tiles

� calcined clay (e.g. metakaolin)

� rice-husk ash

SUPPLEMENTARY CEMENTITIOUS MATERIALS

...Modern concrete looks a lot like Roman concrete

�Using SCMS we can manipulate:

�Cost

�Workability/Rheology

�Setting

�Heat of hydration

�Early strength

�Late strength

�Resistance to chemical attack

�Environmental impact

THE POWER OF SCMS

� Heat released from the reaction of cement and water

HEAT OF HYDRATION

WHY DOES TEMPERATURE MATTER?

� Heat increases the rate of cement hydration (→ more heat)

� Mechanical property development is af fected by temperature

� f’c, f’t, E, creep, CTE, set time

� Thermal stresses can develop due to temperature gradients,

resulting in cracking risks

� High temperatures during curing can increase risk of cracks due to

delayed ettringite formation (DEF)

0

10

20

30

40

50

60

70

80

0 24 48 72 96 120 144 168

Concrete Age (hours)

Tem

pera

ture

(°C

)

75ºF (24ºC) Placement, 470 lb/cy Cement.



Middle Temperature

Max. Temperature Difference

Temp. Limit for DEF

CALORIMETRY: TOOL TO MEASURE HEAT

OF HYDRATION

� Heat of Solution Calorimetry (ASTM C 186)

� Isothermal Calorimetry

� Adiabatic Calorimetry

� Semi-adiabatic Calorimetry

� Measures the power needed to keep a reference cell at the

same temperature of the sample cell

� Good research tool for understanding cement reaction

kinetics with additives and under dif ferent temperature

conditions

ISOTHERMAL CALORIMETRY

ISOTHERMAL CALORIMETRY:

EFFECT OF TEMPERATURE ON HYDRATION

Ty I Tx Lehigh, 20% Rockdale

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000

Paste age (Seconds)

He

at

Evo

lve

d (

J)

5 C

15 C

23 C

38 C

60 C

23 C

38 C

15 C

60 C

5 C


EFFECT OF TEMPERATURE ON HYDRATION


0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 50,000 100,000 150,000 200,000 250,000 300,000

Paste age (Seconds)

Estim

ate

of

De

gre

e o

f H

yd

ratio

n

5 C

15 C

23 C

38 C

60 C

23 C38 C

15 C

60 C

5 C

Cumulative

Heat Evolved

Total Heat

Available

� Some SCMs (Class F fly ash shown here) have no effect on

cement hydration seen by isothermal calorimetry

� Do show that reducing cement content reduces heat of system


EFFECT OF SCM ON HYDRATION

0

1

2

3

4

5

0 10 20 30 40

No

rma

lize

d H

ea

t F

low

(mW

/g c

em

en

titi

ou

s m

ate

ria

l)

Time (h)

100% I/II

80% I/II + 20% FF1

70% I/II + 30% FF1

60% I/II + 40% FF1

0

1

2

3

4

5

0 10 20 30 40

No

rma

lize

d H

ea

t F

low

(mW

/g

ce

me

nt)

Time (h)

100% I/II

80% I/II + 20% FF1

70% I/II + 30% FF1

60% I/II + 40% FF1


EFFECT OF SCM ON HYDRATION

0

1

2

3

4

5

0 10 20 30 40

No

rma

lize

d H

ea

t F

low

(mW

/g c

em

en

titi

ou

s m

ate

ria

l)

Time (h)

100% I/II

80% I/II + 20% FF1

70% I/II + 30% FF1

60% I/II + 40% FF1

� Some SCMs can act

as nucleation sites,

enhancing cement

hydration

SCM EFFECTS ON HYDRATION

S. Bishnoi, “Vector Modelling of Hydrating Cement

Microstructure and Kinetics,” EPFL, 2008.

Lothenbach, B., Scrivener, K., Hooton, R.D. (2011)

Supplementary cementitious materials. Cement

and Concrete Research, 41 (12), 1244-1256.

� Some SCMs are more complex

� Class C fly ash influences the hydration of the aluminate

phases

SCM EFFECTS ON HYDRATION

Gurney, L., Bentz, D.P., Sato, T., and Weiss, W.J. , “ Using Limestone to Reduce Set Retardation in High Volume Fly

Ash Mixtures: Improving Constructability for Sustainability,” TRB 2012 Annual Meeting.

Class C fly ash Class F fly ash

With TiO2or limestone of varying median particle sizes added

32.0

50.0

68.0

86.0

104.0

122.0

140.0

158.0

0.0 24.0 48.0 72.0 96.0 120.0

Time from Mixing (Hrs)

Tem

pera

ture

(°F

)

0

10

20

30

40

50

60

70

Tem

pera

ture

(°C

)

Cement Only

40% Class C

Fly Ash

40% Class F

Fly Ash

� Temperature of a concrete cylinder measured in insulated

system with measured rate of heat loss

� Compensate for heat loss to calculate temperature under

an adiabatic condition

15

SEMI-ADIABATIC CALORIMETRY

SCMS – SEMI-ADIABATIC

0.0

2.0

4.0

6.0

8.0

0 10 20 30 40 50


Rate

of

Heat

Evo

luti

on

(W

/kg

)

100% C2

80% C2, 20% FF1

70% C2, 30% FF1

60% C2, 40% FF1

0.0

2.0

4.0

6.0

8.0

0 10 20 30 40 50


Rate

of H

eat E

volu

tion (W

/kg) 100% C2

80% C2, 20% FC2

70% C2, 30% FC2

60% C2, 40% FC2

CONVERSION OF SEMI-ADIABATIC DATA

TO ADIABATIC DATA

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 1 10 100 1000

Test Duration (hours)

Ge

nera

ted

He

at (k

W/m

^3

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Deg

ree

of H

yd

ratio

n

Generated Heat

Degree of Hydration

α(te) = α at equivalent age t

e, α

u= ultimate α, β = hydration slope parameter, τ= hydration time parameter (hrs),

te= equivalent age (hrs)

Qh(t) is the heat released with

time in an adiabatic condition.

Degree of hydration (αt) is the heat released

at time t (Ht), divided by theoretical total heat

that can be released (Hu)

Fit this equation to experimental

degree of hydration data

CONVERSION OF SEMI-ADIABATIC DATA

TO ADIABATIC DATA

Arrhenius equation:

-5

-4

-3

-2

-1

0.0028 0.0030 0.0032 0.0034 0.0036 0.0038

1/Temperature (1/°K)

ln[k(T)] E=21,153 J/mol


0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 50,000 100,000 150,000 200,000 250,000 300,000

Paste age (Seconds)

Estim

ate

of

De

gre

e o

f H

yd

ratio

n5 C

15 C

23 C

38 C

60 C

23 C38 C

15 C

60 C

5 C

-

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 1 10 100 1000


Gen

era

ted

Heat

(W/m

3)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Deg

ree o

f H

yd

rati

on

Generated Heat

Degree of Hydration

70

80

90

100

110

120

130

140

150

160

170

180

190

200

0 24 48 72 96 120 144


Se

mi-

Ad

iab

ati

c C

on

cre

te T

em

pe

ratu

re (

°F)

Measured

Calculated

False Adiabatic

True Adiabatic

TYPICAL SEMI-ADIABATIC TEST

RESULTS

EFFECTS OF CURING TEMPERATURE

ON ADIABATIC TEMPERATURE RISE

0

10

20

30

40

50

60

1 10 100 1000 10000

Equivalent Age (hours)

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)

29.1 °C

19.0 °C

13.4 °C

28.9 °C

20.7 °C

15.0 °C

100%

Cement C1

30% SCM FF2,

70% Cement C1

EFFECTS OF W/CM ON ADIABATIC

TEMPERATURE RISE

0

10

20

30

40

50

60

1 10 100 1000 10000


Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)

w /cm = 0.42

w /cm = 0.40

w /cm = 0.32

EFFECTS OF CEMENTITIOUS MATERIAL

CONTENT ON ADIABATIC TEMPERATURE

RISE

0

10

20

30

40

50

60

1 10 100 1000 10000


Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)658 pcy Cementitious (379 kg/m3)

564 pcy Cementitious (325 kg/m3)

470 pcy Cementitious (271 kg/m3)

EFFECTS OF AGGREGATE TYPE ON

ADIABATIC TEMPERATURE RISE

0

10

20

30

40

50

60

1 10 100 1000 10000


Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)

Siliceous River Gravel;

Ty F HRWR

Limestone;

Ty F HRWRSiliceous River Gravel;

Ty A&D LRWR

EFFECTS OF CEMENT TYPE ON


0

10

20

30

40

50

60

1 10 100 1000 10000


Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)

100% Cement C1; Ty. F HRWR

100% Cement C2

100% Cement C6

100% Cement C8

100% Cement C9

EFFECT OF FLY ASH ON


0

10

20

30

40

50

60

1 10 100 1000 10000


Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)

80% C2, 20% FF1

70% C2, 30% FF1

60% C2, 40% FF1

100% C2

0

10

20

30

40

50

60

1 10 100 1000 10000


Ad

iab

ati

c T

em

pera

ture

Ris

e (

°C)

0

12

24

36

48

60

72

84

96

108

Ad

iab

ati

c T

em

pera

ture

Ris

e (

°F)

80% C2, 20% FC1

70% C2, 30% FC1

60% C2, 40% FC1

70% C2, 30%FC1 , 0.35% WRRET

100% C2

WHY DOES TEMPERATURE MATTER?

� Heat increases the rate of cement hydration (→ more heat)

� Mechanical property development is af fected by temperature

� f’c, f’t, E, creep, CTE, set time

� Thermal stresses can develop due to temperature gradients,

resulting in cracking risks

� High temperatures during curing can increase risk of cracks due to

delayed ettringite formation (DEF)

0

10

20

30

40

50

60

70

80

0 24 48 72 96 120 144 168


Tem

pera

ture

(°C

)




Middle Temperature

Max. Temperature Difference

Temp. Limit for DEF

WWW.TEXASCONCRETEWORKS.COM

� Thermal predictions are made based on:

� Concrete materials and proportions

� Concrete environment (member size and type, formwork, weather)

� Prediction model was built using an extensive database of

calorimetry, concrete mechanical and thermal cracking frame

testing, and field data

� Validated using real, instrumented concrete structures

HOW CONCRETEWORKS WORKS

�Materials

� Concrete mixture

proportions

� SCMs

� Chemical admixtures

� Aggregate and cement

types

�Activation energy is

automatically

calculated, but can

manually override

�Conditions

� Type of concrete

member, size, and shape

�Date and location of

placement (USA)

� can override with manual

temperature inputs

� Fresh concrete

temperature

� Formwork type

� Curing method

INPUT DATA

� Software will proportion concrete mixtures for desired

compressive strength and slump using ACI 211 volumetric

method

� Concrete strength can be predicted using the maturity method

(if you input the calibration constants)

� Corrosion modeling based on inputs of steel type, cover depth,

and exposure class

ADDITIONAL OUTPUTS

EFFECT OF PLACEMENT TIME ON

TEMPERATURE

Max temp

Min temp

Ambient temp

Max temp difference

Temperature development predicted by ConcreteWorks for a 1m x 1m concrete

column placed in Houston, Texas on August 15 using the default concrete mixture

design

Placed at 10am Placed at 10pm

20°C difference

EFFECT OF PLACEMENT TEMPERATURE

ON TEMPERATURE

Max temp

Min temp

Ambient temp

Max temp difference

Placed at 10am Placed at 10am, reduced fresh

temperature



design

20°C difference

REDUCING FRESH TEMPERATURE

EFFECT OF SCMS ON TEMPERATURE

Max temp

Min temp

Ambient temp

Max temp difference

Placed at 10am Placed at 10am, 30% Class F fly ash



design

20°C difference


Max temp

Min temp

Ambient temp

Max temp difference

Placed at 10am Placed at 10am, 30% Class C fly ash



design

20°C difference


Max temp

Min temp

Ambient temp

Max temp difference

Placed at 10am Placed at 10am, 30% GGBF Slag



design

20°C difference

37

CRACKING RISK EXAMPLE:

5FT X 8FT (1.5 X 2.4M) COLUMN

�Goals:

�Virtually place concrete with at most a medium level

of cracking probability

�Optimize mixture to allow for faster form cycling

�Limestone and siliceous aggregates are available

�Class F fly ash and grade 120 GGBFS are available

�75°F (24°C) placement temperature

�First attempt:

�No SCMs

�Siliceous aggregate (fine and coarse)

�Remove forms after 4 days

38

~40°C

39

TRY CHANGING THE MIXTURE

� Use limestone coarse aggregate

� Use 30% Class F fly ash (will improve workability, and lower

water demand)

� Use a higher dose of Type A low range water reducer – reduce

cement content to 5.5 sacks/yd3 (~300 kg/m3)

� Change placement time to 5pm

� Try dif ferent form removal times

40

~40°C

42

74°C 58°C

27°C

QUESTIONS?Acknowledgements:

Texas Department of Transportation

Prof. Kevin Folliard (UT Austin)

Prof. Anton Schindler (Auburn University)

Prof. Kyle Riding (Kansas State University)

Dr. Jon Poole (CTL Group)

References:

• Riding, K.A., Poole, J.L., Schindler, A.K., Juenger, M.C.G. and

K.J. Folliard, “Quantification of effects of fly ash type on

concrete early-age cracking,” ACI Materials Journal, 105 [2],

149-155, March-April 2008.

• Poole, J.L., Riding, K.A., Juenger, M.C.G., Folliard, K.J. and

A.K. Schindler, “Effects of supplementary cementitious

materials on apparent activation energy,” Journal of ASTM

International, 7 [9], September 2010.

• Riding, K.A., Poole, J.L., Folliard, K.J., Juenger, M.C.G. and

A.K. Schindler, “Modeling the hydration of cementitious

systems,” ACI Materials Journal, 109 [2] 225-233, March-

April 2012.

MORE REFERENCES:


K.J. Folliard, “Temperature boundary condition models for

concrete bridge members,” ACI Materials Journal, 104 [4],

379-387, July-August 2007.


K.J. Folliard, “Effects of construction time and materials on

bridge deck cracking,” ACI Materials Journal, 106 [5], 448-

454, September-October 2009.

• Riding, K.A., Poole, J.L., Schindler, A.K., Juenger, M.C.G.,

and K.J. Folliard, “Statistical determination of cracking

probability for mass concrete,” ASCE Journal of Materials in

Civil Engineering, accepted.

juenger - thermal cracking

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