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

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 Final Set 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 Temperature on Strength

Cold-Weather Concreting Early-Age Strength

Cold-Weather Concreting Retaining Heat of Hydration

Cold-Weather Concreting n Type 30 High-early-strength cement n Additional portland cement (60 to 120 kg/m 3 ) n Chemical accelerators Methods to accelerate strength gain:

Cold-Weather Concreting

Effect of F/T on Strength of Non-Air-Entrained Concrete

Cold-Weather Concreting

Permissible Concrete Temperatures at Placing Thickness of Section, m Temperature, °C MinimumMaximum Less than More than CSA A23.1

Cold-Weather Concreting Effect of Temperatures of Materials on Concrete Temperature 0.22(T a M a + T c M c ) + T w M w + T wa M wa 0.22(M a + M c ) + M w + M wa T = T = temperature of the freshly mixed concrete, °C T a, T c, T w, and T wa = temperature in °C of aggregates, cementing materials, added mixing water, and free water on aggregates, respectively M a, M c, M w, and M wa = mass, kg, of aggregates, cementing materials, added mixing water, and free water on aggregates, respectively

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 or more

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 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 2121 No load, exposed, but later has favorable moist- curing Partial load, exposed64 Fully stressed, exposedSee next slide (B)

Cold-Weather Concreting Recommended Duration of (B) Concrete Temp. in Cold Weather Fully stressed, exposed, air-entrained concrete Required % of standard- cured 28-day strength Days at 10°CDays at 21°C 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

Cold-Weather Concreting Cold-Weather Insulation, Aboveground

Cold-Weather Concreting ness of Thermal Resistance (R) for 10-mm Thickness of Material Board and Slabs Density kg/m 3 (m 2. ° C)/W Expanded polyurethane Expanded polystyrene Mineral fiberboard Plywood Loose fill Wood fiber, soft woods Vermiculite

Cold-Weather Concreting Insulating Blankets Thermal resistance of mineral fibre blanket (50 to 70-mm thick) 1.2 (m 2 ·°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 u M = maturity factor u  = summation u C = concrete temperature, °C u  t = duration of curing at temperature °C, usually in hours

Cold-Weather Concreting

Video Concreting on Ground