Cold-Weather Concreting
NMRMCAA Meeting
November 7, 2007
Albuquerque, NM
Ken Wylie
Principal Materials Engineer
AMEC Earth & Environmental
Cold Weather


Average daily
temperature
<5ºC (40ºF) for
3 successive
days
Stays <10ºC
(50ºF) for more
than ½ of any
24h period
(ACI 306 Definition)
Concrete Components
Cement
 Water
 Fine
Aggregate
 Coarse
Aggregate

Hydration Basics
Cement Particle
Early Stage of Hydration
Hydration Stages (73 ºF)
Setting Times at
Different Temperatures
Rule of Thumb

“For every 10°C (18°F) reduction in
concrete temperature, the times of setting
of the concrete double...”
Effect of Temperature on
Strength Development
Effect of Low Temperatures
on Strength
Hydration
Ceases at…
14 ºF
Whoops!!!
Effect of Casting
Temperature on Slump
Relationship
Between
Temperature,
Slump and Air
Content
Rule 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 Freezing

Fresh Concrete
Up to 50% reduction of
ultimate strength can
occur if frozen —



Within a few hours
Before reaching a
strength of 3.5 MPa (500
psi)
Frozen only once at an
early age —



With curing nearly all
strength can be restored
Less resistance to
weathering
More permeable
Evaporation of
Surface Moisture
from Concrete
Inch-Pound
Air Entrainment for Safety
Concrete considered to ultimately be
“unexposed” may well be exposed during
construction.
Surface Temperature Limitations
(ACI 306)


Above freezing (at least 35°F)
No more than 10 °F higher than minimum
placement temp.
Cold-Weather Concreting
Methods to accelerate strength
gain:



Type III or HE highearly-strength cement
Additional portland
cement (60 to 120
kg/m3 or 100 to 200
lb/yd3)
Chemical accelerators
Early-Age Strength
Accelerating Admixtures
ASTM C 494 or AASHTO M 194, Type C
Accelerate the rate of:
 Hydration (setting)
 Early-age strength gain
Calcium chloride accelerators:
 Increase drying shrinkage,
potential reinforcement corrosion,
potential scaling
 Darken concrete
Example of Non-Chloride
Accelerator Effect on Set Time
Mix @ 50 °F (10 °C)
Plain
Accel. @ 20 fl oz/cwt
(1300 mL/100 kg)
Accel. @ 40 fl oz/cwt
(2600 mL/100 kg)
Initial Set
(h:min)
13:44
Difference
(h:min)
REF
7:11
- 6:33
6:05
- 7:39
Non-Chloride Accelerator Caution
Quote from typical accelerator literature

“… 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.”
Recommended Concrete Temperatures—
Air-Entrained Concrete (ACI 306)
Line
1
2
3
4
Condition
Minimum
Above
temperature of -1°C (30°F)
fresh concrete -18°C to -1°C
as mixed for
(0°F to 30°F)
weather
Below -18°C
indicated.
(0°F)
Minimum temperature of fresh
concrete as placed and
maintained.
Thickness of sections, mm
(in.)
Less than
300 (12)
300 to 900
(12 to 36)
16°C (60°F)
13°C (55°F)
18°C (65°F)
16°C (60°F)
21°C (70°F)
18°C (65°F)
13°C (55°F)
10°C (50°F)
Effect of Temperature of Materials
on Concrete Temperatures
T=
0.22(TaMa + TcMc) + TwMw + TwaMwa
0.22(Ma + Mc) + Mw + Mwa
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 Materials


Water
Aggregates
Heating Mix
Water
NRMCA 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.
Admixtures


Protect from
freezing
Agitate if
necessary
Recommended Duration of
Temperature
Air-entrained concrete
Protection from early-age
freezing
Service category
No load, not exposed,
favorable moist-curing
No load, exposed, but
later has favorable
moist-curing
Partial load, exposed
Fully stressed, exposed
For safe stripping
strength
Convent.
concrete,
days
High-early
strength
concrete,
days
Convent.
concrete,
days
High-earlystrength
concrete,
days
2
1
2
1
3
2
6
4
3
2
See next slide
Recommended Duration of
Temperature
Fully stressed, exposed, air-entrained concrete
Days at 10°C (50°F)
Days at 21°C (70°F)
Required
percentage of
Type of portland cement
Type of portland cement
standard-cured
28-day
strength
I or GU II or MS III or HE I or GU II or MS III or HE
50
6
9
3
4
6
3
65
11
14
5
8
10
4
85
21
28
16
16
18
12
95
29
35
26
23
24
20
Retaining Heat of Hydration
Cold-Weather
Insulation,
Aboveground
Insulating Blankets
Thermal resistance of
mineral fiber blanket
(50 to 70-mm [2 to 2.75-in.]
thick)
1.2
7
(m2·K)/ (°F·hr·ft2)/
W
Btu
Thermal Resistance, R, for (10-mm [1in.] Thick) Insulating Materials
Board and Slabs
Expanded polyurethane
2)/B
(°F·hr·ft
(m2·K)/W
tu
0.438
6.25
Expanded polystyrene
0.277
4.0
Mineral fiberboard
0.204
2.94
Plywood
0.087
1.24
0.231
3.33
0.148
2.13
Loose fill
Wood fiber, soft woods
Vermiculite
Enclosures




Wood
Canvas
Tarpaulins
Polyethylene
Film
Heated Enclosure
Direct-Fired
Heater
Indirect-Fired Heater
Hydronic Systems
Protect from Thermal Shock
Cooling After Protection
Maximum Temperature Drop in 24 Hours
Section size, minimum dimensions, mm (in.)
Less than
300 (12)
28°C
(50°F)
300 to 900 900 to 1800
(12 to 36)
(36 to 72)
22°C
(40°F)
17°C
(30°F)
Over
1800 (72)
11°C
(20°F)
Maturity Concept
Metric:
Inch-Pound:
M =  (C + 10) t
M =  (F – 14) t
where





M = maturity factor
 = summation
C = concrete temperature, degrees
Celsius
F = concrete temperature, degrees
Fahrenheit
t = duration of curing at temperature C
(F), usually in hours
Thank You!