Cold-Weather Concreting. Cold Weather When air temp. is at or below 5°C or when there is a...

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