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Maturity: The alternative to traditional strength specifications

WCPA 2019 Annual ConferenceFebruary 14, 2019

WCPA Annual Concrete Pavement Workshop February 14, 2019

Wisconsin Concrete Pavement Association 1

• The plan:– Discuss concrete maturity

method.– Review implementation.– Present technology

available for implementation.



What is tradition?WCPA Annual Concrete Pavement Workshop February 14, 2019


Presenter

Presentation Notes

4

50ºF

73ºF

1.5-m lifts

Lift 28

Maturity bridges the gap…

What is tradition?

Courtesy: NIST



Presenter

Presentation Notes

WILLOW ISLAND COOLING TOWER�WEST VIRGINIA, 1978 Previous day’s lift unable to support construction loads. Collapsed scaffolding and gantry. 51 fatalities. Average air temperature less than 10°C (50°F). No method to accurately estimate in-place strength.

What is Maturity?• ASTM C 1074

– A technique for estimating concrete strength that is based on the assumption that samples of a given concrete mixture attain equal strengths if they attain equal values of the maturity index.

• AASHTO T 325– The extent of development of concrete properties that are dependent on cement

hydration and pozzolanic reactions.• ACI (306R)

– tests performed to estimate in-place concrete strength using in-place concrete temperature history and strength versus temperature history functions derived from tests of concrete with comparable mixture proportions.

• Wisconsin DOT– Maturity testing is an alternative to compressive strength tests for administering

timing of job control functions such as ending the curing period or cold-weather protection periods, opening to service, or removal of forms or false work.



Presenter

Presentation Notes

Arrhenius Method: te

Nurse-Saul: TTF

∑ ∆⋅= −−t

TTQe tet sa

0

)/1/1(

( )∑ ∆⋅−=t

oC tTTM0

Concrete Age

PCC

Tem

pera

ture

24 h

ours

afte

r pl

acem

ent

What is Maturity?WCPA Annual Concrete Pavement Workshop February 14, 2019


7

Courtesy FHWA: http://www.fhwa.dot.gov/pavement/pccp/pubs/06004/



Presenter

Presentation Notes

“Concrete of the same mix at the same maturity has approximately the same strength whatever combination of temperature and time go to make up that maturity.” A.G.A. Saul, 1951

8

50ºF

73ºF

Maturity = 778 C-hrsDay 4Strength = 3000psi

Maturity bridges the gap…

Maturity = 778 C-hrsDay 3Strength = 3000psi

1.5-m lifts

Lift 28

Courtesy: NIST



Maturity Highs• Benefits

– Increased safety– Expedited construction schedules– Improved construction methods

• Advantages– Provides instant predictions of in-place strength– Not operator dependent– Not specimen dependent– Simple test method/Portable equipment– Accurate, efficient, and consistent

Build safe.

Build faster.

Build better.

Save money.



Presenter

Presentation Notes

The maturity method is a non destructive test method to evaluate the concrete in situ strength. Benefits may include expedited construction schedules, increased safety, improved construction methods

• Measures only time and temperature.

• Does not account for humidity conditions during curing.

• Mix specific.

• May not fully characterize long-term strength.

Maturity LowsWCPA Annual Concrete Pavement Workshop February 14, 2019


Implementation



Guidance Documents• National

• ASTM C 1074• AASHTO T 325• ACI

• ACI 228.1R In-Place Methods to Estimate Concrete Strength• ACI 308R Guide to Curing Concrete• ACI 301 Specifications for Structural concrete• ACI 318-08/318M-08 Building Code Requirements for Structural Concrete and Commentary• ACI 306.1 Specification for Cold Weather Concreting

• State• Construction and Materials Manual Chapter 8 Section 70• 2019 Standard Specifications Section 415 Concrete Pavement• 2019 Standard Specifications Section 502 Concrete Bridges



1. Create the Maturity Curve.

2. Place sensors in the field.

3. Use the maturity curve to determine strength in the field.

4. Validate the maturity curve.

Steps for Implementation to Evaluate Strength



1. Create the maturity curve.

• Cast test specimens from a trial batch that represents the mix that will be used in the field.




• Embed a sensor in at least one on the test specimens.

• It is recommended that a second sensor be embedded in a second specimen.

• For cylinders, place the sensor in the center.

• For beams, place the sensor in the center of the beam and 1/3 away from the end.




• Store all specimens in the same environment.




• Break at least two specimens at specified intervals.

• Break at 24hrs, 72 hrs, 7 days, 14 days, and 28 days.

• If you are looking for strength values before the first 24-48 hrs, break additional sets within that period. The goal is to have a few data points before and after your target strength.



1. Create the maturity curve.WCPA Annual Concrete Pavement Workshop February 14, 2019


7day

0

1000

2000

3000

4000

5000

6000

0 2000 4000 6000 8000 10000 12000 14000 16000

MATURITY INDEX, TTF (°C-HR)

CO

MPR

ESSI

VE S

TREN

GTH

(PS

I)

1day

3day

14day

28day


Test ID Age (hrs)

Strength (psi)

Maturity(C-hr)

Cylinder Set A 24 1500 1500

Cylinder Set B 72 3000 3800

Cylinder Set C 168 3600 5900

Cylinder Set D 336 4100 9850

Cylinder Set F 672 4400 16000

Example data sheet for recording information:

y = 893 ln(x) - 3516R2 = 0.99



2. Place sensors in the field.WCPA Annual Concrete Pavement Workshop February 14, 2019


3. Use the maturity curve

0

1000

2000

3000

4000

5000

6000

0 2000 4000 6000 8000 10000 12000 14000 16000MATURITY INDEX, TTF (°C-HR)C

OM

PRES

SIVE

STR

ENG

TH (

PSI)

y = 893 ln(x) - 3516R2 = 0.99



Presenter

Presentation Notes

It is a relationship between temperature and time to strength gain. In a nutshell, you collect internal concrete temperature data as the concrete hardens and calculate and calculate a maturity index value. Sing that maturity index value, you estimate concrete strength using a maturity curve.

3. Use the maturity curveWCPA Annual Concrete Pavement Workshop February 14, 2019


4. Validate the curve.Verify with supplemental tests.

• In-place tests such as cast in place cylinders, penetration resistance, and pullout strength. (873, C803, and C900)

• Early-age compressive strength tests of standard cured specimens of concrete as-delivered, subjected to accelerated curing, or field-molded cylinders instrumented with maturity sensors. (C918, C684, C31)

Measured strengths of cylinders are compared with maturity-estimated strengths to validate the curve. If deviation of > 10% is consistently

exceeded, a new curve should be developed.



4. Validate the curve.

• Compare estimated strength to actual strength.

• If within 10%, good to go!

VS



Maturity Systems



Maturity - In Situ Strength EvaluationTemperature Monitoring

• Mass Placement

• Cold Weather Placement

• Hot Weather Placement

• Fast-Track Construction• Form Removal• Post Tensioning• Sawcutting• Repair• Opening to traffic

• Precast• Quality Control

Typical ApplicationsWCPA Annual Concrete Pavement Workshop February 14, 2019


What are my options?Thermocouple wire

systemsWireless Systems

Wired Systems



What are my options?Thermocouple Systems



Presenter

Presentation Notes

Consider: Affordable Exposed data collector Connectors not always weather proof Cables must be connected all the time

Wired Systems

What are my options?WCPA Annual Concrete Pavement Workshop February 14, 2019


Presenter

Presentation Notes

Consider Affordable Data is stored on the sensor in the concrete

Wireless Systems: Bluetooth –embedded vs nonembedded transmitters



Wireless Systems: Cellular



Wireless Systems: Combination



Conclusions• Maturity is a relationship between time and temperature and strength.• Maturity is calculated from time and temperature history.• Maturity bridges the gap between break tests and in-place concrete

and can reduce the number of break tests required in the field.• Evaluating maturity is a non-destructive test method for an ESTIMATE of

in-place strength gain.• Maturity implementation includes 4 major steps.• Maturity systems are used for temperature monitoring and

implementing maturity to estimate in-place strength.• There are a number of options when it comes to maturity systems.

