As the temperature of the concrete mix increases, what is the effect on the concrete mix?

As the temperature of the concrete mix increases, what is the effect on the concrete mix?

• A. its strength is increased
• B. the finishing time increases
• C. there is a loss in slump
• D. there is an increase in slump

Answer: (C)

Workability, or slump, of a fresh concrete mix is sensitive to temperature. When the mix is hotter, hydration reactions proceed faster and the paste stiffens more quickly, so the mix becomes less flowable. That means the slump decreases as temperature rises. So the correct effect is a loss in slump. Finishing time tends to decrease with heat because the concrete sets faster, and while early strength can rise with higher temperatures, the immediate workability is reduced, not increased.

Workability, or slump, of a fresh concrete mix is sensitive to temperature. When the mix is hotter, hydration reactions proceed faster and the paste stiffens more quickly, so the mix becomes less flowable. That means the slump decreases as temperature rises. So the correct effect is a loss in slump. Finishing time tends to decrease with heat because the concrete sets faster, and while early strength can rise with higher temperatures, the immediate workability is reduced, not increased.