cold-weather concreting. cold weather when air temp. is at or below 5°c or when there is a...
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Cold-Weather Concreting
Cold-Weather Concreting
Cold Weather
When air temp. is at or below 5°C or when there is a probability of it falling below 5°C within 24 hours of placing —
CSA A23.1
Cold-Weather Concreting
Cold-Weather Concreting
Effect of Freezing Fresh Concrete Up to 50% reduction of ultimate
strength can occur if frozen — within a few hours before reaching a str. of 3.5 MPa
Frozen only once at an early age —
With curing nearly all strength can be restored
Less resistance to weathering More permeable
Cold-Weather Concreting
Relationship Between Initial Set and Casting Temperature
Cold-Weather Concreting
Relationship Between FinalSet and Casting Temperature
Cold-Weather Concreting
Relationship Between Slump and Casting Temperature
Cold-Weather Concreting
Effect of Temperature on Strength Development
Cold-Weather Concreting
Effect of Low Temperatureon Strength
Cold-Weather Concreting
Early-Age Strength
Cold-Weather Concreting
Retaining Heat of Hydration
Cold-Weather Concreting
Cold-Weather Concreting
Type 30 High-early-strength cement
Additional portland cement (60 to 120 kg/m3 )
Chemical accelerators
Methods to accelerate strength gain:
Cold-Weather Concreting
Cold-Weather Concreting
Effect of F/T on Strength of Non-Air-Entrained Concrete
Cold-Weather Concreting
Cold-Weather Concreting
Permissible Concrete Temperatures at Placing
Thicknessof Section, m
Temperature, °C
Minimum Maximum
Less than 0.3
0.3-1
1-2
More than 2
10
10
5
5
35
30
25
20
CSA A23.1
Cold-Weather Concreting
Effect of Temperatures of Materials on Concrete Temperature
0.22(TaMa + TcMc) + TwMw + TwaMwa
0.22(Ma + Mc) + Mw + Mwa
T =
T = temperature of the freshly mixed concrete, °C
Ta, Tc, Tw, and Twa = temperature in °C of aggregates, cementing materials, added mixing water, and free water on aggregates, respectively
Ma, Mc, Mw, and Mwa = mass, kg, of aggregates, cementing materials, added mixing water, and free water on aggregates, respectively
Cold-Weather Concreting
Cold-Weather Concreting
Max. Permissible Temp. Differential Between Concrete Surface and Ambient Air — Wind up to 25 km/hr.
Thickness of
concrete,
m
Max. permissible temp. differential, °C
L to H ratio of structure
0 3 5 7 20 or more
0.3
0.6
0.9
1.2
1.5
29
22
18
17
16
22
18
16
15
14
19
16
15
14
13
17
15
14
13
13
12
12
12
12
12
Cold-Weather Concreting
Checking Fresh Concrete Temperatures
Cold-Weather Concreting
Checking Hardened Concrete Temperatures
Cold-Weather Concreting
Temperature of Test Cylinders
Cold-Weather Concreting
Recommended Duration of (A) Concrete Temp. in Cold Weather
Air-entrained concreteAir-entrained concrete
Service category
Protection from early-age freezing
For safe stripping strength
Convent. concrete,
days
High-early strength concrete,
days
Convent.
concrete, days
High-early-strength concrete,
days
No load, not exposed, favorable moist-curing
2 1 2 1
No load, exposed, but later has favorable moist-curing
3 2
3 2
Partial load, exposed 6 4
Fully stressed, exposed
See next slide (B)
Cold-Weather Concreting
Recommended Duration of (B) Concrete Temp. in Cold Weather
Fully stressed, exposed, air-entrained concreteFully stressed, exposed, air-entrained concrete
Required % of standard-cured 28-day strength
Days at 10°C Days at 21°C
Type of portland cement
Type of portland cement
10 I or GU
20 II or MS
30 III or HE
10 I or GU
20 II or MS
30 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
Cold-Weather Concreting
Cold-Weather Insulation, Aboveground
Cold-Weather Concreting
Thermal Resistance (R) for 10-mm Thickness ofness of Material
Board and SlabsDensity
kg/m3(m2 . °C)/W
Expanded polyurethane 24 0.438
Expanded polystyrene 29 0.277
Mineral fiberboard 256 - 272 0.204
Plywood 545 0.087Loose fill
Wood fiber, soft woods 32 - 56 0.231
Vermiculite 112 - 131 0.148
Cold-Weather Concreting
Insulating Blankets
Thermal resistance of mineral fibre blanket (50 to 70-
mm thick)
1.2
(m2 ·°C)/W
Cold-Weather Concreting
Insulating Concrete Forms (ICF)
Cold-Weather Concreting
Insulated Column Forms
High-density plywood
Rigid polystyrene
Rough plywood
Cold-Weather Concreting
Enclosures
Wood Canvas Tarpaulins Polyethylene Film
Cold-Weather Concreting
Heated Enclosure
Cold-Weather Concreting
Direct-Fired Heater
Cold-Weather Concreting
Indirect-Fired Heater
Cold-Weather Concreting
Hydronic Systems
Cold-Weather Concreting
Maturity Concept
M = (C + 10) t
where M = maturity factor = summation C = concrete temperature, °C t = duration of curing at temperature
°C, usually in hours
Cold-Weather Concreting
Cold-Weather Concreting
Video
Concreting on Ground