Cold-Weather Concreting
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Transcript of 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!