Retarding admixtures used in hot-weather concrete reduce the possibility of surface crusting.

• A. True
• B. False
• C. Sometimes true
• D. Not specified

Answer: (B)

A retarding admixture slows cement hydration and the early set, which can help with workability and temperature rise in hot weather. But surface crusting happens when the exposed surface dries out and stiffens before the interior has adequately hydrated. Delaying the set does not inherently prevent that rapid surface moisture loss, and if curing isn’t managed, the surface can still form a crust or even be more prone to it because the surface remains pliable longer while evaporation continues. So retarding admixtures do not reduce the possibility of surface crusting in hot weather; proper curing and evaporation control are the effective measures.