maturity slides by carino

8/13/2019 Maturity Slides by Carino

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The Maturity Method: A Simple

Approach for EstimatingEarly-Age Strength

Development of Concrete

Dr. Nicholas J. Carino

Consultant

International Symposium on

Advances in Concrete TechnologyJanuary 9-13, 2012

Quito, Ecuador

Strength of Concrete Time

Temperature

Strength

Age

High T

LowT

S

S

t


2/23

Maturity Method

Technique to account for the combinedeffects of time and temperature onstrength development of concrete

Can be used to estimate in-place strengthat any time during constructionNeed to measure in-place temperature

Need the strength-maturity relationship ofthe concrete

Origins

Need for a technique to estimate strengthdevelopment under steam curing

McIntosh, J. D., 1949, Electrical Curing ofConcrete, Magazine of Concrete Research,Vol. 1, No. 1, January, pp. 21-28.

Nurse, R. W., 1949, Steam Curing ofConcrete, Magazine of Concrete Research,

Vol. l, No. 2, pp. 79-88. Saul, A. G. A., 1951, Principles Underlying the

Steam Curing of Concrete at AtmosphericPressure, Magazine of Concrete Research,Vol. 2, No. 6, March, pp. 127-140.


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Maturity Rule

"Concrete of the same mix at the samematurity (reckoned in temperature-time)has approximately the same strengthwhatever combination of temperatureand time go to make up that maturity."

A.G.A. Saul, 1951

Maturity Rule Samples of the same concrete with same maturity

have same strength

Strength

Maturity Index, M

StrengthMaturityRelationship

Temp

erature

Time

To

M

Hot

Temp

erature

Time

To

M

Cold

M


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Maturity MethodASTM C1074

Developed in 1987

TerminologyASTM C 1074

Maturity

Maturity method

Maturity index

Maturity function

Strength-maturity relationship


5/23

Terminology

Maturity

The extent of the development of aproperty of a cementitious mixture.

Note: At any age, maturity depends onthe curing history (time and temperature)

Terminology

Maturity method

Technique to estimate concrete strengthbased on the assumption that samples ofthe same concrete have equal strengthsif they have equal values of the maturity

index


6/23

Terminology

Maturity indexAn indicator of maturity calculated from themeasured temperature history using a maturityfunction.(Note: The calculated index is indicative of maturityprovided there has been sufficient moisture forhydration during the time used in the calculation.)

Two indexes are used:

Temperature-time factorEquivalent age

Terminology

Maturity function

A mathematical expression that uses the measuredtemperature history during the curing period tocalculate a maturity index that is indicative of thematurity at the end of that period.

Nurse-Saul function (for temp-time factor) Arhennius function (for equivalent age)


7/23

Maturity Functions

Nurse-Saul Function Temperature-time factor:

Arrhenius Equation Equivalent Age:

tTTtM a )()( 0

tet raTT

Q

e

11

Ta = Avg. concrete temperatureT0 = Datum temperature

Q = Temperature sensitivity factorTr = Reference temperature (in K)

Test smart Build right

Temperature-time FactorNurse-Saul Function

Time

ConcreteTemp.

To t

Ta

tTTtM a )()( 0


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Equivalent Age, teThe number of days or hours of curing at areference curing temperature (Tr) required toproduce a maturity equal to the maturityachieved by a curing period (t) at anothertemperature (T):

te = (T) t

(T) = Age conversion factor

1 1

( ) a rQ

T TT e


Effect of Q-Value on (T)Tr = 23 C (296 K)

0

1

2

3

4

5

6

0 10 20 30 40 50

Q = 4000 K

Q = 5000 K

Q = 6000 K

AgeConversionFactor

Temperature,oC


9/23

Courtesy of TxDOT

Maturity Meters

Maturity Index Temperature-Time

Factor

Equivalent Age


Modern Maturity Meters

Sensor and data logger in oneembeddable unit

Maturity read by handheld readeror temperature data transferredto handheld computer

Or wireless data transfer

Courtesy of The Transtec Group


10/23

"COMA" Disposable Meter

Components

0

1

2

3

4

5days @

20 C

Cap

Capillary

Card

Plastic tube

Break Capillary

0

1

2

3

4

5days @

20 C

EquivalentAge @ 20C

Evaporation rate from capillary is affected by temperaturein the same way as strength development of concrete.


Break capillary Place tube intofresh concrete

Read concretematurity

Use of COMA Meter


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Implementation

ASTM C 1074

Permits maturity functions based on Nurse-Saul or Arrhenius equations

Procedure to establish strength-maturityrelationship

Procedure to estimate in-place strength

Annex for determining best value of To or Q

Terminology

Strength-maturity relationship

An empirical relationship betweencompressive (or flexural) strength andmaturity index obtained by testingspecimens whose temperature history up tothe time of test has been recorded.


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Strength-Maturity Relationship

Prepare cylinders (or cubes)

Embed temperature sensors at centerof two cylinders (or cubes)

Moist cure

At ages of 1, 3, 7, 14, and 28 d measurestrength and corresponding maturityindex

Plot average compressive strengthversus maturity index

Instrumented Specimen

Courtesy of TxDOT


13/23

Strength-Maturity Relationship

Plowman:

Carino-Knudsen:

Freiesleben Hansen-Pederson:

)log(MbaS

)(1

)(

0

0

MMK

MMKSS

u

M

uS S e


Example of S-M Relationship

1000

2000

3000

4000

5000

6000

7000

10

15

20

25

30

35

40

45

0 4000 8000 12000 16000

S = -5942.1 + 2947log(M)R= 0.98208

CompressiveStrength,psi

Temperature-Time Factor, (oC-h)

Compres

siveStrength,

MPa

1 d

3d

7 d

14 d28 d

Best-ft Equation:

Plowman Logarithmic Equation


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Example of S-M Relationship

Plowman Logarithmic Equation

1000

2000

3000

4000

5000

6000

7000

10

15

20

25

30

35

40

45

100 1000 10000 100000

y = -5942.1 + 2947log(x)

R= 0.98208

Com

pressiveStrength,psi


Com

pressiveStrength,

MPa

1 d

3d

7 d 14 d

28 d

Best-ft Equation:

Estimating In-place Strength

Secure sensors to reinforcement or embedsensors into concrete a soon as practicable At critical locations in terms of exposure and

structural requirements

Connect sensors to maturity instruments

Read maturity index

Estimate strength from strength-maturityrelationship


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Install Sensor

Courtesy of Con-Cure Corp.

Maturity

Meter


Courtesy of TxDOTCourtesy of Con-Cure Corp.

Read Meter


16/23

1000

2000

3000

4000

5000

6000

7000

10

15

20

25

30

35

40

45

0 4000 8000 12000 16000

S = -5942.1 + 2947log(M)R= 0.98208

CompressiveStrength,psi


Co

mpressiveStrength,

MPa

1 d

3d

7 d

14 d28 d

Best-ft Equation:

Estimate Strength

Strength

Maturity Index

Summary

S

14.3

FieldMeasurement

MaturityMeter

MM

Laboratory Testing

7.2

MaturityMeter


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Limitations

Moisture must be available for hydration

Neglects effects of early-age temperature onlater-age strength

Only temperature is measured; need other teststo confirm concrete strength Early-age tests (ASTM C918) of standard-cured

specimens (from field): confirm strength potential

Pullout tests (ASTM C900): confirm in-place strength

Test instrumented specimens from field samples: verifyS-M relationship (Texas DOT Method Tex 426-A)

Maturity + Pullout Testing

Use the maturity method to determine whenthe required strength should have beenachieved in the structure

Verify by using pullout tests to estimate in-place strength

Combination of maturity and pullout testing canlead to rapid and safe concrete construction


18/23

Maturity Functions

Nurse-Saul Function Temperature-time factor:

Arrhenius Equation Equivalent Age:

tTTtM a )()( 0

tet raTT

Q

e

11

Ta = Avg. concrete temperatureT0 = Datum temperature

Q = Temperature sensitivity factorTr = Reference temperature (in K)

Procedure for To and Q


19/23

Isothermal Strength Gain

Age

Strength

to

kTSu

1

Su

( )

1 ( )

T ou

T o

k t tS S

k t t

Rate Constant, kT

Age

Strength

kT Su

1 Curing at higherT increases kT


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Rate Constant vs. Temperature

Temperature

RateConstant

kT

To

Linear FunctionObtain To

( ) ( )ok T A T T

Rate Constant vs. Temperature

Temperature

RateConstant

kT

Arrhenius EquationObtain Q

273( )

Q

Tk T Ce


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ExampleLinear function

Carino & Tank, ACI Journal, Mar-April 1992

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-10 0 10 20 30 40 50

Type IType I + FA

RateConstant,day-1

TemperatureoC

-5 C

11 C

w/cm = 0.45

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-10 0 10 20 30 40 50

Type IType I + FA

Rate

Constant,day-1

TemperatureoC

ExampleArrhenius equation

Carino & Tank, ACI Journal, Mar-April 1992

Q = 7640 K

Q = 3610 K

w/cm = 0.45


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Summary

Maturity method is a simple technique forestimating in-place strength

Removal of formwork

Application of prestressing

Termination of cold-weather protection or curing

Open structure to service

Accuracy of estimated strength depends on :

Using appropriate maturity function (To, Q) Good control of batching operations

Recognize that maturity method:

Measures only temperature Additional confirmation about the in-place concrete

is needed before applying construction loads

Assumes that adequate moisture is present forhydration Proper curing is required

Does not account for effects of high early-agetemperature on later-age strength Develop S-M at higher curing temperature


23/23

Muchas gracias!

maturity slides by carino

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