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MASS CONCRETE: FROM THEORY TO PRACTICEJOHN GAJDA, PE, FACI - MJ2 CONSULTING, PLLC

OSCAR R. ANTOMMATTEI, MS, PE, FACI - KIEWIT ENGINEERING GROUP

JUSTIN TORKILSON, EI - KIEWIT ENGINEERING GROUP

• John Gajda, PE 31 jurisdictions, FACI

• Principal at MJ2 Consulting, PLLC

• Former Chair of ACI 207 Mass and Thermally Controlled Concrete (2010 to 2016)

• ACI 301 Specifications for Structural Concrete Subcommittee Chair of “Mass Concrete”

• 1000+ Mass Concrete Projects over the past 25+ years

ABOUT THE PRESENTER

• Oscar R. Antommattei, MS, PE, FACI

• ACI 301-H Specifications for Structural Concrete - Mass Concrete

• ACI 207 Mass and Thermally Controlled Concrete

• ACI 305 Hot Weather ConcreteCommittee Chair

• CSA A23.1/.2 Concrete Materials Construction and Testing Standards

• 100+ thermal control projects

• 18+ years concrete industry experience

• Justin Torkilson, EI

• Concrete Engineer with Kiewit Engineering Group, Inc.

• ACI 207 Mass and Thermally Controlled Concrete

• ACI 304 Measuring, Mixing, Transporting and Placing

• 50+ North American thermal control projects

ABOUT THE PRESENTER

• Purpose of Thermal Control

• When is it Mass Concrete?

• Limits

• Strategies

OUTLINE - THEORY

• Prevent avoidable thermal damage

• Cracking during construction

• Future cracking/deterioration

• Achieve service life

PURPOSE OF THERMAL CONTROL(I.E. WHY TREAT A PLACEMENT AS MASS CONCRETE)

excessive temperature difference excessive temperature

• Larger Elements

• Higher Strengths

• Flowable Concrete

• Rapid Construction

• Long Service Life

• Less Desirable Aggregates

• Fly Ash Shortages

TRENDS THAT LEAD TO MASS CONCRETE

All result in increased concrete temperatures!

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• Purpose of Thermal Control

• When is it Mass Concrete?

• Limits

• Strategies

OUTLINE - THEORY

Mass concrete is: “any volume of concrete in which a combination of dimensions of the member being cast, the boundary conditions, the characteristics of the concrete mixture, and the ambient conditions can lead to

as a result of elevated concrete temperature due to heat from hydration”– American Concrete Institute (ACI), 2010 and 2016

WHAT IS MASS CONCRETE?

undesirable thermal stresses, cracking, deleterious chemical reactions, or reduction in the long-term strength

WHAT IS MASS CONCRETE?

Other Stuff: Self Consolidating Concrete (SCC), Drilled Shafts, Grout, High Early Strength Concrete, Highway Patches, etc.

WHAT IS MASS CONCRETE?

• When rate of heat generation and thickness is such that heat is generated faster than it escapes.

• No requirements in ACI 207

• Per ACI 301:

• Only when the EOR specifies it to be mass concrete

• Thickness ≥4 ft.

• >660 lbs/yd3 cementitious (2010 edition; not in current edition)

• DOTs: ≥2.5 to >7 ft.

WHEN IS IT MASS CONCRETE? WHEN IS IT MASS CONCRETE?

Published:

• When Should Mass Concrete

Requirements Apply?, Aspire Bridge

Magazine, Summer 2015.

• Proposed Mass Concrete Definition Based

on Concrete Constituents and Minimum

Dimension, ACI SP325, Fall 2018.

Adopted:

Not yet, but in draft versions of ACI 207.1R

and ACI 207.2R.

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EQUIVALENT CEMENT CONTENT (ECC)

ECC = portland cement + factor*slag cement + 0.5*fly ash (class F) +0.8*fly ash (class C) +1.2*(silica fume + metakaolin)

Slag (0-20%) 1.0-1.1

Slag (20-45%) 1.0

Slag (45-65%) 0.9

Slag (65-80%) 0.8

• Purpose of Thermal Control

• When is it Mass Concrete?

• Limits

• Strategies

OUTLINE - THEORY

• Maximum Temperature

• Can reduce durability and ultimate strength

• Temperature Difference

• Can result in thermal cracking

• Thermal Shock

• Don’t stop thermal control too soon!

LIMITS NEEDED FOR …

• Purpose

• Prevent DEF (delayed ettringite formation)

• Avoid potential reduction ofin-place strength

>185°F per PCA documents

MAXIMUM TEMPERATURE

• Potential long term durability issue that can occur only when all three of the following occur:

• Concrete temperature exceeds 158/160°F

• Cementitious materials have a particular chemistry

• External water available during service life

• Expansion and cracking 1+ year from now

DELAYED ETTRINGITE FORMATION (DEF)

• Limits to Prevent DEF

• Safe limit (ACI 301): 158/160°F (70°C)

• ACI 201: up to 185°F (85°C) only when

• ≥25% class F fly ash,

• ≥ 35% slag cement or class C fly ash

• Typical Specifications

• Illinois: 150°F

• Massachusetts: 154°F

• Most: 158 or 160°F

• Florida: 165/180°F

• Canada (CSA): 158/167/185°F

MAXIMUM TEMPERATURE LIMITS

Upper values with high levels of fly ash and/or slag cement

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TEMPERATURE DIFFERENCE LIMIT

•Purpose

•Prevent/minimize thermal cracking

• Types of Limits

• Constant (i.e. 35°F or 20°C)

• Stepped (i.e. 20-35-50°F over time)

• Engineered/Tailored

• Constant Limit

• “Discovered” nearly 100 years ago

• Commonly specified (35°F is ACI 301 default)

• Easy to use

• Conservative

• Canada (CSA): 36/45°F

TEMPERATURE DIFFERENCE LIMITS

Upper value when testing shows that the concrete has a low coefficient of thermal expansion (CTE)

• Age-Stepped Limit

• Also easy to use

• Less conservative than constant limit

TEMPERATURE DIFFERENCE LIMITS

Iowa DOT

• 20°F for hours 0 to 24

• 30°F for hours 24 to 48

• 40°F for hours 48 to 72

• 50°F beyond 72 hours

Pennsylvania DOT

• 36°F for hours 0 to 48

• 40°F for hours 48 to 72

• 50°F beyond 72 hours

• Engineered (tailored) limit

• Accounts for concrete’s ability to withstand higher thermal

stresses as strength increases

• Based on measured concrete

properties and structure

• ACI 207.2R-95 and

CIRIA C660

TEMPERATURE DIFFERENCE LIMITS

0

10

20

30

40

50

60

70

80

0 1000 2000 3000 4000 5000 6000 7000

Tem

pe

ratu

re D

iffe

ren

ce

Lim

it, °F

In-Place Compressive Strength, psi

Mix No. 4660

Mix No. 4661

Excessive (above the line)

Acceptable (below the line)

• Don’t remove thermal controls too soon; interior must cool sufficiently

• ACI 301: thermal control until center cools to within the temperaturedifference limit ofambient

THERMAL SHOCK PREVENTION

• Purpose of Thermal Control

• When is it Mass Concrete?

• Limits

• Strategies

OUTLINE - THEORY

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• Low Heat Concrete

• Use less cement

• Higher cementreplacement levels

CONTROL STRATEGIES

Temp Rise (°F) = 0.16*ECC

ECC = portland cement + factor*slag cement + 0.5*fly ash (class F) +0.8*fly ash (class C) +1.2*(silica fume + metakaolin)

Up to 50% fly ash or 75% slag

Slag (0-20%) 1.0-1.1

Slag (20-45%) 1.0

Slag (45-65%) 0.9

Slag (65-80%) 0.8

• Reduced placement sizes (with adequate time for cooling)

CONTROL STRATEGIES (CONT.)

• Keep the surface warm

• Surface insulation

• Time ≈ ¾*Thickness-1

• No exposed steel!

• Added heat?

CONTROL STRATEGIES (CONT.)

• Precool the concrete

• Use cold batch water

• 2-3°F reduction

• Replace batch water with ice (hard frozen, not slush)

• Up to 20°F reduction

• Liquid nitrogen precooling

• Unlimited precooling

CONTROL STRATEGIES (CONT.)

• Post-cool with cooling pipes

• Remove internal heat after placement

• Reduces the temperature rise and maximum temperature

• Reduces the time of thermal control

• ¾” or 1” dia. plastic pipe

• Often filled with grout

CONTROL STRATEGIES (CONT.) COOLING PIPES

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• Monitor temperatures to ensure (prove) limits not exceeded

• Typical locations

• Geometric center of placement

• 2-3” below the surface at center of large surface

• Hourly data

TEMPERATURE MONITORING

• Poor insulation

• Uninsulated steel

• Water curing

THINGS TO AVOID

1. Analytical Modeling

2. Thermal Control Plan

3. Field Implementation

4. Verification and Validation

5. Revise and Update

AN APPROACH TO MASS CONCRETE TEMPERATURE RISE – SEMI-ADIABATIC TEST

Semi-Adiabatic (Test Block)

73°F

Full-Adiabatic(Calculated)

87°F+ Computer

Modeling =

Fresh concrete placing temperature

Semi-Adiabatic (Test Block)

73°F+ =

THERMAL MODELING

1. Analytical Modeling

2. Thermal Control Plan

3. Field Implementation

4. Verification and Validation

5. Revise and Update

AN APPROACH TO MASS CONCRETE

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WHAT IS A THERMAL CONTROL PLAN?

• Thermal control plan is a TOOL for the Contractor to plan and execute mass placements:

✓ Control and monitor temperature

✓ Reduce thermal shrinkage

✓ Minimize thermal cracks

• Understanding behavior, challenges and effects:

✓ Mixture proportions and constituents

✓ Placing cycles, heat sinks, formwork/insulation

✓ Maximum temperature and temp difference

✓ Duration of thermal control and monitoring

✓ Corrective measures (pre-cooling or post-cooling)

1. Analytical Modeling

2. Thermal Control Plan

3. Field Implementation

4. Verification and Validation

5. Revise and Update

AN APPROACH TO MASS CONCRETE

FIELD TEMPERATURE MONITORING PRE-COOLING

INSULATION INSULATION

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HEATING POST COOLING – COOLING PIPES – SPILLWAY EXAMPLE

POST-COOLING END THERMAL CONTROL MEASURES?

Tmax = 147°F

Tdiff = 12°F

50°F35°F

EXAMPLE – SUMMARY OF THERMAL RESULTS

Ambient

Temp1

Concrete

Temp2

Max

Core

Temp

Max

Temp

Diff

End

Thermal

Control4

Max

Core

Temp

Max

Temp

Diff

End

Thermal

Control4

Max

Core

Temp

Max

Temp

Diff

End

Thermal

Control4

Max

Core

Temp

Max

Temp

Diff

End

Thermal

Control4

F° F° F° F° Days F° F° Days F° F° Days F° F° Days

90 159 50 N/A 166 37 5.5 171 25 7.5 175 16 10.5

80 149 43 N/A 155 32 5.0 160 22 7.0 164 14 9.5

70 139 37 N/A 145 27 4.5 149 19 6.5 153 12 8.5

90 153 60 N/A 161 44 6.0 168 31 9.0 173 20 12.5

80 142 53 N/A 150 39 5.5 157 28 8.0 161 18 12.0

70 132 46 N/A 139 35 5.0 145 24 7.5 150 16 11.0

60 121 39 N/A 128 30 4.5 134 21 7.0 138 14 10.0

50 111 31 N/A 117 25 4.0 123 18 6.5 127 12 9.0

90 147 71 N/A 157 52 7.0 165 36 10.0 171 23 15.0

80 133 62 N/A 144 46 6.5 152 32 9.5 158 21 14.0

70 120 52 N/A 130 40 6.0 139 29 9.0 145 19 13.0

60 107 42 N/A 117 34 5.5 125 25 8.5 132 16 12.0

50 93 33 N/A 103 28 5.0 112 21 8.0 119 14 11.5

70 107 59 N/A 121 47 6.5 132 34 9.5 141 22 13.5

60 91 47 N/A 105 40 6.0 117 29 9.0 127 19 12.5

50 76 36 N/A 90 32 5.5 102 25 8.5 112 17 12.0

1.        Ambient temperature is defined as average a i r ambient and/or surroundings temperatures .

2.        Concrete temperature is defined as temperature of fresh concrete at time of placement in the formwork.

3.        R-Value of insulating blankets placed over curing method on a l l exposed finished surfaces and on a l l formed s ides of concrete, in2-hr-°F /BTU.

4.        Estimated time to end of thermal control (days) i s based on the time that temperature di fference between core and ambient i s not greater than 27°C.

5.        Refer to Cold Weather Protection Plan to determine cold weather protective measures .

50

305

90

70

Thermal Control Table

Block Pedestal

4500 PSI | 65% Grade 100 Slag

No Insulation Light Insulation3 Moderate Insulation3 Heavy Insulation3

1. Ambient temperature is defined as average air ambient and/or surroundings temperatures.

2. Concrete temperature is defined as temperature of fresh concrete at time of placement in the formwork.3. R-Value of insulating blankets placed over curing method on all exposed finished surfaces and on all formed sides of concrete, in2-hr-°F /BTU.

4. Estimated time to end of thermal control (days) is based upon the time that the temperature difference between core and ambient is not greater

than 50°F. 5. Refer to Hot and Cold Weather Protection Plan to determine hot and cold weather protective measures.

1. Analytical Modeling

2. Thermal Control Plan

3. Field Implementation

4. Verification and Validation

5. Revise and Update

AN APPROACH TO MASS CONCRETE

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VERIFICATION AND VALIDATION

6.5 ft

VERIFICATION AND VALIDATIONS/N: 9560692 9563135 9560259 8443100 8458430

Job: PEDBRG PEDBRG PEDBRG TOP1 PEDBRG PEDBRG

Location: MID1 MID2 TOP 1 TOP2 AMBNT TEMP

Logger Subtype ID: 9 9 9 9 9

Run State:Run Run Run Run Run

Start Date: 2/6/2020 11:28 2/6/2020 11:29 2/6/2020 11:25 2/6/2020 11:27 2/6/2020 11:49

Last Download Date:2/14/2020 16:56 2/14/2020 16:56 2/14/2020 16:55 2/14/2020 16:56 2/14/2020 16:54

Elapsed Time (hrs): 197.47 197.45 197.5 197.48 197.08

Data Interval (min): 60 60 60 60 60

Number of readings: 198 198 198 198 198

Current Reading:

Time (hrs)Temperature (°F) Temperature (°F) Temperature (°F) Temperature (°F) Temperature (°F)

197.47 123.8 123.8 95 95 73.4

Maximum 159.8 158 120.2 122

Logged Readings (198):

Time(hrs) Temperature (°F) Temperature (°F) Temperature (°F) Temperature (°F) Temperature (°F)

0 35.6 35.6 41 39.2 51.8

1 41 41 51.8 50 44.6

2 48.2 46.4 53.6 51.8 42.8

3 71.6 68 48.2 48.2 42.8

4 73.4 71.6 46.4 44.6 39.2

5 73.4 71.6 46.4 46.4 39.2

6 73.4 73.4 69.8 68 39.2

7 77 75.2 68 68 39.2

8 82.4 80.6 68 68 37.4

9 89.6 87.8 68 68 33.8

10 96.8 96.8 69.8 69.8 33.8

11 109.4 107.6 71.6 73.4 33.8

12 118.4 116.6 77 77 35.6

13 123.8 122 82.4 82.4 39.2

14 131 129.2 87.8 89.6 39.2

15 134.6 132.8 96.8 96.8 37.4

16 138.2 134.6 100.4 102.2 41

17 140 138.2 104 105.8 42.8

18 141.8 140 105.8 107.6 35.6

VERIFICATION AND VALIDATION

1. Analytical Modeling

2. Thermal Control Plan

3. Field Implementation

4. Verification and Validation

5. Revise and Update

AN APPROACH TO MASS CONCRETE

• When a revision or update may be necessary:

✓ All field conditions are known, but the model is inaccurate and not conservative

✓ All field conditions are known, but the model is inaccurate and highly conservative

✓ Proposed change to construction sequence, materials, means/methods, etc.

• When a revision or update may not be necessary:✓ Inadequate field implementation

✓ Different field conditions

✓ Concrete mix changes

✓ Formwork or insulation changes

✓ Unknown field operations change

REVISE AND UPDATE CLOSING REMARKS

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THANK YOU!John Gajda, PE, FACIMJ2 Consulting, PLLC847-922-1886

John@MJ2consulting.com

www.ThermalControlPlan.com

Oscar R. Antommattei, MS, PE, FACI Kiewit Engineering Group

Chief Concrete Engineer / Materials

Engineering Manager

Justin Torkilson, EIKiewit Engineering Group

Concrete Engineer

Questions?

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