NASCLA Accredited Commercial General ContractorConcreteMedium
A concrete contractor is planning the finishing operations for a large industrial floor slab. The specifications call for a hard-troweled finish suitable for heavy forklift traffic. After screeding, bull floating, and waiting for the bleed water to evaporate, the crew begins the next step. Which of the following finishing operations should immediately follow the disappearance of bleed water to achieve the specified hard-troweled finish?
- AFinal hand troweling.
- BApplying a curing compound.
- CSaw cutting control joints.
- DPower floating (or darbying if by hand).
Show answer & explanationAnswer & explanation
Correct answer: D. Power floating (or darbying if by hand).
After the bleed water has evaporated and the concrete has gained initial set (i.e., it can support a finisher's weight with minimal indentation), the next step for a hard-troweled finish is usually power floating (or darbying for smaller areas). This operation further embeds the aggregate, smooths the surface, and prepares it for subsequent troweling passes to achieve the desired hard, dense finish.
Why the other options are wrong
- A. Final hand troweling is performed after power floating, once the concrete is much stiffer, to achieve the densest, hardest finish.
- B. Curing compounds are applied after all finishing operations are complete.
- C. Saw cutting control joints is typically done later, after the concrete has gained sufficient strength to prevent raveling, but before significant shrinkage cracking occurs.
Concrete Finishing Sequence
The ordered series of operations performed on fresh concrete to achieve a desired surface texture, flatness, and durability.
- Timing is crucial for each step.
- Starts after concrete placement, ends with curing.
- Varies based on desired final finish.
Memory trick: Screed, Float, Wait, Float, Trowel, Cure.