Which statement best describes control of slab curling in low-slump concrete?

Which statement best describes control of slab curling in low-slump concrete?

• A. The only control is how much water is added to the truck to raise slump, and adding water will increase shrinkage and curling
• B. Curling is unaffected by water content and only depends on ambient temperature
• C. Final troweling speed is the sole determinant
• D. Curling can be completely prevented by curing with plastic sheeting

Answer: (A)

Curling in a low-slump slab happens mainly because of differential shrinkage as moisture leaves the concrete and the slab experiences temperature changes. The amount of water in the mix sets how much shrinkage the concrete will undergo later; adding water to raise slump increases the overall moisture that can evaporate, which raises drying shrinkage and can worsen curling. So, controlling how much water is added to achieve the desired slump is the most direct way to influence curling in this scenario: less unnecessary water means less potential shrinkage and less curling. Ambient temperature and finishing speed matter, but they aren’t the sole determinants. Temperature affects how the concrete cools and shrinks, and finishing techniques influence surface properties, yet curling is driven largely by internal shrinkage and moisture gradients. Curing with plastic sheeting helps reduce plastic shrinkage early on, but it cannot completely prevent curling, because curling can still develop from later drying and temperature gradients after the plastic film is removed.

Curling in a low-slump slab happens mainly because of differential shrinkage as moisture leaves the concrete and the slab experiences temperature changes. The amount of water in the mix sets how much shrinkage the concrete will undergo later; adding water to raise slump increases the overall moisture that can evaporate, which raises drying shrinkage and can worsen curling. So, controlling how much water is added to achieve the desired slump is the most direct way to influence curling in this scenario: less unnecessary water means less potential shrinkage and less curling.

Ambient temperature and finishing speed matter, but they aren’t the sole determinants. Temperature affects how the concrete cools and shrinks, and finishing techniques influence surface properties, yet curling is driven largely by internal shrinkage and moisture gradients. Curing with plastic sheeting helps reduce plastic shrinkage early on, but it cannot completely prevent curling, because curling can still develop from later drying and temperature gradients after the plastic film is removed.