An admixture that reduces bleeding while retarding setting will aggravate crusting problems. True or False?

An admixture that reduces bleeding while retarding setting will aggravate crusting problems. True or False?

• A. True
• B. False
• C. Not sure
• D. It depends

Answer: (A)

Bleed water keeps the surface hydrated and helps wash fines away, which favors a smoother, less crusty finish. Crusting forms when the top layer loses moisture and stiffens into a hard skin while the interior is still plastic. If an admixture reduces bleeding, there’s less surface water available to keep the top layer moist and flush away fines. At the same time, retarding setting slows hydration, so the surface remains pliable longer but dries out more slowly, giving evaporation a chance to create a crust before the paste fully gains strength. This combination makes crusting more likely, so the statement is true.

Bleed water keeps the surface hydrated and helps wash fines away, which favors a smoother, less crusty finish. Crusting forms when the top layer loses moisture and stiffens into a hard skin while the interior is still plastic. If an admixture reduces bleeding, there’s less surface water available to keep the top layer moist and flush away fines. At the same time, retarding setting slows hydration, so the surface remains pliable longer but dries out more slowly, giving evaporation a chance to create a crust before the paste fully gains strength. This combination makes crusting more likely, so the statement is true.