ACI Flatwork Finisher flashcards
ACI Flatwork Finisher · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Water-cement ratio
- Weight of water divided by weight of cement in a mix. Lower ratios increase strength and durability but reduce workability.
- Slump test
- ASTM C143 test measuring concrete consistency by the vertical drop of a slumped cone. Typical flatwork slump is 3-5 inches.
- Air entrainment
- Intentional microscopic air bubbles in concrete that provide freeze-thaw resistance. Flatwork typically targets 5-7 percent air.
- Cubic yard volume
- Concrete volume in cubic yards equals length times width times thickness in feet, divided by 27.
- Hydration
- Chemical reaction between cement and water that hardens concrete and releases heat. It continues for weeks, reaching design strength near 28 days.
- Aggregate proportion
- Coarse and fine aggregates make up roughly 60-75 percent of concrete volume; cement paste fills the remaining space.
- 28-day strength
- Standard age at which concrete compressive strength is specified and tested, though strength continues to gain slowly afterward.
- Mix ratio notation
- A 1:2:3 mix means one part cement, two parts fine aggregate, and three parts coarse aggregate by volume.
- Bull float
- A long-handled tool used after bleed water disappears to level ridges, embed aggregate, and consolidate the slab surface before floating.
- Bleed water
- Water that rises to the slab surface after placement. Finishing while it is present causes blistering, delamination, or weak surfaces.
- Control joint depth
- Control joints should be cut to about one-quarter of slab thickness to create a weakened plane that controls cracking location.
- Joint spacing rule
- Control joint spacing in feet is typically 24-36 times slab thickness in inches. A 4-inch slab gives roughly 8-12 feet.
- Edging
- Rounding slab edges with a radius of about one-quarter to one-half inch to resist chipping and improve appearance.
- Steel trowel
- A finishing tool that densifies and smooths the surface, producing a hard, durable finish. Used after floating, not on bleed water.
- Broom finish
- A slip-resistant texture created by dragging a dampened broom across the surface, typically perpendicular to traffic direction.
- Curing compound
- A liquid membrane applied after finishing to slow moisture loss and support hydration. Apply at the manufacturer's specified coverage rate.
- Magnesium float
- A hand or power tool that opens the concrete surface and removes high spots, preparing it for troweling or texturing.
- Evaporation rate risk
- Evaporation above about 0.1 lb/ft2/hr sharply raises plastic shrinkage cracking risk. Use windbreaks, fog spray, or evaporation retarder.
- Plastic shrinkage cracks
- Shallow, parallel cracks that form within hours of placement when surface moisture evaporates faster than bleed water rises.
- Drying shrinkage cracks
- Longer cracks that appear weeks to months after placement as hardened concrete loses moisture. Control joints manage their location.
- Hot-weather limit
- Concrete temperature at placement should generally not exceed about 90 F (32 C). Cool aggregates or use ice to control temperature.
- Cold-weather protection
- Keep concrete at 50 F (10 C) or above until it reaches about 500 psi to prevent freeze damage to early-age concrete.
- Retarder
- An admixture that slows cement hydration and extends set time, useful in hot weather or for complex placements.
- Superplasticizer
- A high-range water reducer that increases slump without added water. Slump loss can occur within 30-90 minutes of mixing.
- Crazing
- A network of fine surface cracks caused by rapid drying of the surface layer. It is usually cosmetic and shallow.
- Scaling
- Surface flaking of the finished slab, often caused by freeze-thaw cycles, deicing salts, or finishing while bleed water is present.
- FF/FL numbers
- Floor Flatness (FF) and Floor Levelness (FL) values from ASTM E1155. Higher FF means a flatter floor; FF 50+ suits narrow aisles.
- Industrial slab strength
- Warehouse and industrial slabs commonly specify 4,000-5,000 psi with low water-cement ratios around 0.40-0.45.
- Saw-cut timing
- Industrial slabs are typically saw-cut within 6-12 hours of finishing, before random cracking begins, while concrete resists raveling.
- Fiber reinforcement
- Steel or macro-synthetic fibers added to concrete reduce plastic shrinkage cracking and improve impact and toughness performance.
- Laser screed
- A machine-guided screed that levels concrete to precise elevations, improving flatness and levelness on large industrial placements.
- Shrinkage-compensating concrete
- Concrete using expansive cement or additives to offset drying shrinkage, allowing longer joint spacing in industrial floors.