What slump range is typical for a flatwork concrete slab that will be broom-finished?

• A. 1 to 2 inches.
• B. About 4 to 5 inches.
• C. 8 to 9 inches.
• D. 10 to 12 inches.

Answer: (B)

Slump is a measure of how workable or fluid the concrete mix is, which affects how easy it is to place, strike off, and finish. For a flatwork slab that will be broom-finished, you want a balance: enough plasticity to be placed smoothly and to take a broom texture, but not so wet that the surface can smear or wash away the texture.

A slump of about four to five inches provides that balance. It’s fluid enough to spread into the forms and allow a clean, even broom texture, yet stiff enough to hold the surface features and resist excessive bleeding or deformation. If the mix were much stiffer (around 1–2 inches), finishing would be harder and the broom texture would be shallow. If it were very wet (eight to twelve inches), the texture would likely smear, and the surface could bleed and lose definition.