Which of the following is a factor of HWC?

• A. Low wind speeds.
• B. Frost point.
• C. Water vapor.
• D. High ambient temps.

Answer: (D)

Hot weather concreting is driven by environmental conditions that accelerate moisture loss and heat buildup in the mix. The defining factor here is high ambient temperatures, because when the air is hot, the concrete temperature rises and the evaporation rate of mixing water increases. This accelerates hydration, can reduce workability quickly, and raises the risk of plastic shrinkage cracking if curing and protection aren’t managed. Frost point points to cold conditions, so it isn’t a hot-weather factor. Water vapor (humidity) affects evaporation but isn’t the key driver in hot weather, and low wind speeds actually tend to reduce evaporation (windier conditions increase the risk). So, high ambient temperatures are the factor that most characterizes hot weather concreting.