Cold-Weather Concreting

Cold-Weather ConcretingCold-Weather Concreting

NMRMCAA MeetingNMRMCAA Meeting

November 7, 2007November 7, 2007

Albuquerque, NMAlbuquerque, NM

Ken WylieKen Wylie

Principal Materials EngineerPrincipal Materials Engineer

AMEC Earth & EnvironmentalAMEC Earth & Environmental

Cold Cold WeatherWeather

(ACI 306 (ACI 306 Definition)Definition)

Average daily Average daily temperature temperature <5ºC (40ºF) <5ºC (40ºF) for 3 successive for 3 successive days days

Stays <10ºC Stays <10ºC (50ºF) for more (50ºF) for more than ½ of any than ½ of any 24h period24h period

Concrete Concrete ComponentsComponents

CementCement WaterWater Fine Fine

AggregateAggregate Coarse Coarse

AggregateAggregate

Hydration BasicsHydration Basics

Cement Particle

Early Stage of Hydration

Hydration Stages (73 Hydration Stages (73 ººF)F)

Setting Times at Setting Times at Different Different

TemperaturesTemperatures

Rule of ThumbRule of Thumb

“For every 10°C (18°F) reduction in concrete temperature, the times of setting of the concrete double...”

Effect of Temperature Effect of Temperature on Strength on Strength

DevelopmentDevelopment

Effect of Low Effect of Low Temperatures on Temperatures on

StrengthStrength

HydrationHydration

Ceases at…Ceases at…

14 14 ºFºF

Whoops!!!Whoops!!!

Effect of Casting Effect of Casting Temperature on Temperature on

SlumpSlump

Relationship Between Temperature, Slump and Air Content

Rule of ThumbRule of Thumb

“For every 10°C (18°F) reduction in concrete temperature, the times of setting of the concrete double, thus increasing the amount of time that the concrete is vulnerable to damage due to freezing.”

Effect of Effect of Freezing Fresh Freezing Fresh

ConcreteConcrete Up to 50% reduction Up to 50% reduction

of ultimate strength of ultimate strength can occur if frozen —can occur if frozen — Within a few hoursWithin a few hours Before reaching a Before reaching a

strength of 3.5 MPa strength of 3.5 MPa (500 psi)(500 psi)

Frozen only once at Frozen only once at an early age —an early age — With curing nearly all With curing nearly all

strength can be strength can be restoredrestored

Less resistance to Less resistance to weathering weathering

More permeableMore permeable

Inch-PoundInch-Pound

Evaporation of Evaporation of Surface Surface

Moisture from Moisture from ConcreteConcrete

Air Entrainment for SafetyAir Entrainment for SafetyConcrete considered to ultimately be “unexposed” may well be exposed during construction.

Surface Temperature Surface Temperature LimitationsLimitations

(ACI 306)(ACI 306) Above freezing (at least 35Above freezing (at least 35°F)°F) No more than 10 °F higher than No more than 10 °F higher than

minimum placement temp.minimum placement temp.

Cold-Weather Cold-Weather ConcretingConcreting

Type III or HE high-Type III or HE high-early-strength cementearly-strength cement

Additional portland Additional portland cement (60 to 120 cement (60 to 120 kg/mkg/m33 or 100 to 200 or 100 to 200 lb/ydlb/yd33))

Chemical acceleratorsChemical accelerators

Methods to accelerate strength gain:

Early-Age Early-Age StrengthStrength

Accelerating Accelerating AdmixturesAdmixtures

Accelerate the rate of:Accelerate the rate of: Hydration (setting)Hydration (setting) Early-age strength gainEarly-age strength gain

ASTM C 494 or AASHTO M 194, Type CASTM C 494 or AASHTO M 194, Type C

Calcium chloride accelerators: Increase drying shrinkage,

potential reinforcement corrosion, potential scaling

Darken concrete

Example of Non-Chloride Example of Non-Chloride Accelerator Effect on Set TimeAccelerator Effect on Set Time

Mix @ 50 °F (10 °C)

Initial Set (h:min)

Difference (h:min)

Plain 13:44 REF

Accel. @ 20 fl oz/cwt (1300 mL/100 kg)

7:11 - 6:33

Accel. @ 40 fl oz/cwt (2600 mL/100 kg)

6:05 - 7:39

Non-Chloride Accelerator Non-Chloride Accelerator CautionCaution

“… the concrete producer should account for the water contained in the (accelerator). Each Liter of (accelerator) added to a concrete mix will contribute 0.78 kg (6.5 lbs/gal) of water to that mix.”

Quote from typical accelerator literature

Recommended Concrete Recommended Concrete Temperatures—Air-Entrained Temperatures—Air-Entrained

Concrete (ACI 306)Concrete (ACI 306)

LineLine ConditionCondition

Thickness of sections, Thickness of sections, mm (in.)mm (in.)

Less than Less than 300 (12) 300 (12)

300 to 900 300 to 900 (12 to 36)(12 to 36)

11Minimum Minimum temperature temperature of fresh of fresh concrete as concrete as mixed for mixed for weather weather indicated.indicated.

Above Above -1°C -1°C (30°F)(30°F)

16°C (60°F)16°C (60°F) 13°C (55°F)13°C (55°F)

22-18°C to --18°C to -

1°C (0°F to 1°C (0°F to 30°F)30°F)

18°C (65°F)18°C (65°F) 16°C (60°F)16°C (60°F)

33Below -Below -

18°C (0°F)18°C (0°F) 21°C (70°F)21°C (70°F) 18°C (65°F)18°C (65°F)

44Minimum temperature of Minimum temperature of fresh concrete as placed fresh concrete as placed and maintained.and maintained.

13°C (55°F)13°C (55°F) 10°C (50°F)10°C (50°F)

Effect of Temperature of Effect of Temperature of Materials on Concrete Materials on Concrete

TemperaturesTemperatures0.22(0.22(TTaaMMaa + + TTccMMcc) + ) + TTwwMMww + + TTwawaMMwawa

0.22(0.22(MMaa + + MMcc) + ) + MMww + + MMwawaT =

T = temperature of the freshly mixed concrete, °C (°F)

Ta, Tc, Tw, and Twa = temperature in °C (°F) of aggregates, cement, added mixing water, and free water on aggregates, respectively

Ma, Mc, Mw, and Mwa = mass, kg (lb), of aggregates, cementing materials, added mixing water, and free water on aggregates, respectively

Heating MaterialsHeating Materials

WaterWater AggregatesAggregates

Heating Mix Water

NRMCA Heating CriteriaNRMCA Heating Criteria

For plants seeking certification to supply concrete in subfreezing weather i.e., where concrete is placed regularly during sub-freezing weather, minimum heating capacity for water and/or aggregate of 15 boiler output horsepower per 100 cubic yard average daily cold weather production. (May be reduced to 10 bph if storage capacity permits round-the-clock operation of heating equipment.) One boiler horsepower = 33,500 BTU per hour transferred to the water.

AdmixturesAdmixtures

Protect from Protect from freezingfreezing

Agitate if Agitate if necessarynecessary

Recommended Duration Recommended Duration of Temperatureof Temperature

Air-entrained concreteAir-entrained concrete

Service categoryService category

Protection from early-age Protection from early-age freezingfreezing

For safe stripping For safe stripping strengthstrength

Convent. Convent. concrete, concrete,

daysdays

High-early High-early strength strength concrete, concrete,

daysdays

Convent. Convent. concrete, concrete,

daysdays

High-early-High-early-strength strength concrete, concrete,

daysdays

No load, not exposed, No load, not exposed, favorable moist-curingfavorable moist-curing 22 11 22 11

No load, exposed, but No load, exposed, but later has favorable later has favorable moist-curingmoist-curing 33 22

33 22

Partial load, exposed Partial load, exposed 66 44

Fully stressed, exposedFully stressed, exposed See next slideSee next slide

Recommended Duration of Recommended Duration of TemperatureTemperature

Fully stressed, exposed, air-entrained concreteFully stressed, exposed, air-entrained concrete

Required Required percentage of percentage of standard-cured standard-cured 28-day 28-day strengthstrength

Days at 10°C (50°F)Days at 10°C (50°F) Days at 21°C (70°F)Days at 21°C (70°F)

Type of portland cementType of portland cement Type of portland cementType of portland cement

I or GUI or GU II or MSII or MS III or HEIII or HE I or GUI or GU II or MSII or MS III or HEIII or HE

5050 66 99 33 44 66 33

6565 1111 1414 55 88 1010 44

8585 2121 2828 1616 1616 1818 1212

9595 2929 3535 2626 2323 2424 2020

Retaining Heat of Retaining Heat of HydrationHydration

Cold-Cold-Weather Weather

Insulation, Insulation, AbovegrounAbovegroun

dd

Insulating Insulating BlanketsBlankets

Thermal resistance of Thermal resistance of mineral fiber blanket mineral fiber blanket (50 to 70-mm (50 to 70-mm [2 to 2.75-in.] thick) [2 to 2.75-in.] thick)

1.2 1.2 (m(m22·K)/·K)/

WW

7 7 (°F·hr·ft(°F·hr·ft22)/)/

BtuBtu

Thermal Resistance, R, for (10-Thermal Resistance, R, for (10-mm [1-in.] Thick) Insulating mm [1-in.] Thick) Insulating

MaterialsMaterialsBoard and SlabsBoard and Slabs (m(m22·K)/·K)/

WW(°F·hr·ft(°F·hr·ft22)/)/

BtuBtu

Expanded Expanded polyurethanepolyurethane 0.4380.438 6.256.25

Expanded polystyreneExpanded polystyrene 0.2770.277 4.04.0

Mineral fiberboardMineral fiberboard 0.2040.204 2.942.94

PlywoodPlywood 0.0870.087 1.241.24

Loose fillLoose fill

Wood fiber, soft Wood fiber, soft woodswoods 0.2310.231 3.333.33

VermiculiteVermiculite 0.1480.148 2.132.13

EnclosureEnclosuress

WoodWood CanvasCanvas TarpaulinsTarpaulins PolyethylenPolyethylen

e Filme Film

Heated EnclosureHeated Enclosure

Direct-Fired Direct-Fired HeaterHeater

Indirect-Fired Indirect-Fired HeaterHeater

Hydronic Hydronic SystemsSystems

Protect from Thermal ShockProtect from Thermal Shock

Cooling After Cooling After ProtectionProtection

Section size, minimum dimensions, mm (in.)Section size, minimum dimensions, mm (in.)

Less thanLess than

300 (12)300 (12)

300 to 300 to 900900

(12 to 36) (12 to 36)

900 to 900 to 18001800

(36 to 72)(36 to 72)

OverOver

1800 (72)1800 (72)

28°C 28°C (50°F)(50°F)

22°C 22°C (40°F)(40°F)

17°C 17°C (30°F)(30°F)

11°C 11°C (20°F)(20°F)

Maximum Temperature Drop in 24 Maximum Temperature Drop in 24 HoursHours

Maturity Maturity ConceptConcept

Metric: Metric: M = M = (C + 10) (C + 10) tt

Inch-Pound: Inch-Pound: M = M = (F – 14) (F – 14) tt

wherewhere M = maturity factor M = maturity factor = summation = summation C = concrete temperature, degrees C = concrete temperature, degrees

CelsiusCelsius F = concrete temperature, degrees F = concrete temperature, degrees

FahrenheitFahrenheit t = duration of curing at t = duration of curing at

temperature C (F), usually in hourstemperature C (F), usually in hours

Thank You!Thank You!