Hot Weather ConcretingDesign and Control of Concrete Mixtures – Chapter 16

Overview When to Take Precautions Effects of High Temperatures Cooling Concrete Plastic Shrinkage Cracking Curing and Protection

Hot Weather Concreting Conditions

High ambient/concrete temperature Low humidity Wind Solar radiation

Effects Increased water demand, rate of setting,

plastic shrinkage, thermal cracking, cold joints

Accelerated slump loss Air content variability

When to Take Precautions

When to Take Precautions Possible precautions:

Preconstruction conference Utilize proven mixtures Cool the concrete Reduce batch to finish time Favorable scheduling Reduce evaporation

Effects of High Temperatures

Effects of High Temperature

Effects of High Temperature

Cooling Concrete

Cooling ConcreteT = [0.22 (TaMa + TcMc) + TwMw + TwaMwa]

[0.22(Ma +Mc) +Mw +Mwa]

T = temperature of the freshly mixed concrete Ta, Tc, Tw, and Twa = temperature of aggregates,

cement, added mixing water, and free water on aggregates

Ma, Mc, Mw, and Mwa = mass, kg (lb), of aggregates, cementing materials, added mixing water, and free water on aggregates

T (°F) = [0.22 (TaMa + TcMc) + TwMw + TwaMwa –112Mi]

[0.22(Ma +Mc) +Mw +Mwa +Mi]

Cooling Concrete with IceT (°C) = [0.22 (TaMa + TcMc) + TwMw + TwaMwa –

80Mi] [0.22(Ma +Mc) +Mw +Mwa +Mi]

T = temperature of the freshly mixed concrete Ta, Tc, Tw, and Twa = temperature of aggregates, cement,

added mixing water, and free water on aggregates Ma, Mc, Mw, and Mwa = mass, kg (lb), of aggregates, cementing

materials, added mixing water, and free water on aggregates Mi = mass of ice

Transportation and Placing

Plastic Shrinkage Cracking

Plastic Shrinkage Cracking

Plastic Shrinkage Cracking

Plastic Shrinkage Cracking

Curing and Protection

Heat of Hydration General guideline - temperature rises by

2°C to 9°C per 45 kg 5°F to 15°F per 100 lb

This heat may need to be addressed High heat Massive placements

Summary When to Take Precautions Effects of High Temperatures Cooling Concrete Plastic Shrinkage Cracking Curing and Protection

Questions

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