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. It depends on other factors
• D. Not enough information

Answer: (A)

Crusting is a surface phenomenon where moisture that reaches the surface evaporates while the concrete surface is still plastic and not yet hardened, forming a hard, brittle crust that’s hard to work out later. If an admixture slows setting, the surface stays workable longer, giving an extended window for moisture on the surface to evaporate and for a crust to form. Even if the same admixture reduces the amount of bleed water, the longer plastic period means any small amount of surface moisture can still dry into a crust before finishing can eliminate or blend it. So, the combination of reducing bleeding with a retarder tends to promote crust formation, making the statement true.

Crusting is a surface phenomenon where moisture that reaches the surface evaporates while the concrete surface is still plastic and not yet hardened, forming a hard, brittle crust that’s hard to work out later. If an admixture slows setting, the surface stays workable longer, giving an extended window for moisture on the surface to evaporate and for a crust to form. Even if the same admixture reduces the amount of bleed water, the longer plastic period means any small amount of surface moisture can still dry into a crust before finishing can eliminate or blend it. So, the combination of reducing bleeding with a retarder tends to promote crust formation, making the statement true.