During a concrete pour in Florida's hot climate, the concrete temperature reaches 95°F. What is the primary concern and immediate action required?
Correct Answer
C) Implement cooling measures and extend curing time
High concrete temperatures accelerate hydration and can lead to rapid moisture loss, cracking, and reduced strength. Cooling measures such as chilled water, ice, or shade should be implemented, and extended moist curing is essential.
Why This Is the Correct Answer
When concrete temperature reaches 95°F in hot climates, the hydration process accelerates significantly, leading to rapid water evaporation, potential thermal cracking, and reduced final strength. Cooling measures such as using chilled water, ice substitution for mix water, or providing shade help control the temperature. Extended moist curing becomes critical because the accelerated hydration consumes water faster, requiring longer curing periods to achieve proper strength development and prevent surface cracking.
Why the Other Options Are Wrong
Option A: Increase water content to improve workability
Adding more water to hot concrete actually weakens the mix by increasing the water-cement ratio, which reduces compressive strength and durability. While it may temporarily improve workability, it doesn't address the root problem of excessive heat and creates long-term structural issues.
Option B: Accelerate the pour to finish before setting
Accelerating the pour in hot conditions increases the risk of cold joints, improper consolidation, and finishing problems. Rushing the process when concrete is already setting faster due to heat leads to poor quality work and potential structural defects.
Option D: Add more cement to compensate for heat
Adding more cement to hot concrete actually makes the problem worse by increasing the heat of hydration, which generates even more internal heat. This accelerates the setting time further and increases the risk of thermal cracking and reduced workability.
Memory Technique
Think 'COOL and CURE' - when concrete gets too hot (over 90°F), you must COOL it down and extend the CURE time, just like treating heat exhaustion.
Reference Hint
ACI 305 - Hot Weather Concreting, Chapter on temperature control and cooling methods
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