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Transcript of Hot Weather Concreting - Portland Cement · PPT file · Web view ·...
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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