ACI Flatwork Technician flashcards
ACI Flatwork Technician · 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.
- Slump test
- ASTM C143 test measuring concrete workability by the vertical drop of a cone of concrete; typical flatwork slump is 4-6 inches (100-150 mm).
- Water-cement ratio
- Ratio of water weight to cement weight in a mix; typical flatwork ratio is 0.45-0.55; lower ratios increase strength and durability but reduce workability.
- Air entrainment
- Intentional addition of air bubbles to concrete to improve freeze-thaw durability; recommended air content is 5-7% for 3/4-inch aggregate.
- Curing duration
- Minimum time concrete must stay moist and above 50°F (10°C) to achieve strength; typically 7 days for normal cement, 3 days for high-early strength.
- Contraction joint spacing
- Joints cut to control random cracking; spacing should be 24-36 times slab thickness (e.g., 10-12 ft for a 4-inch slab).
- Isolation joint
- A joint that separates flatwork from structures like walls or columns, allowing independent movement and preventing cracking at connections.
- Concrete yield
- Volume of concrete produced per batch; 1 cubic yard covers 81 ft² at 4 inches thick, 65 ft² at 5 inches, 54 ft² at 6 inches.
- Subgrade compaction
- Preparation of soil beneath a slab; compact to 95% Standard Proctor density and proof-roll to ensure uniform support and prevent settlement.
- Bleed water
- Water that rises to the concrete surface after placement due to settlement of solids; must disappear before finishing to avoid weak, dusty surfaces.
- Bull float
- A long-handled tool with a flat blade used immediately after screeding to smooth the surface, embed aggregate, and remove high spots.
- Troweling
- Finishing operation using a steel trowel to produce a dense, smooth surface; performed after bleed water disappears, with increasing blade pressure and angle.
- Broom finish
- Textured surface created by dragging a broom across concrete; provides slip resistance; use fine broom indoors, coarse outdoors.
- Edging
- Rounding the edges of a slab with an edger tool to reduce chipping; typical radius is 1/4 to 1/2 inch.
- Jointing tool
- Tool used to cut contraction joints in plastic concrete to a depth of about 1/4 of slab thickness, controlling where cracks occur.
- Hot weather concreting
- Practices to prevent rapid moisture loss and early setting: use retarders, cool ingredients, place at night, and cure immediately.
- Cold weather concreting
- Protecting concrete from freezing for at least 24 hours; use accelerators, heated water, and insulating blankets; avoid calcium chloride in air-entrained concrete.
- Screeding
- Leveling freshly placed concrete to the desired grade using a straightedge or screed board; first step in finishing.
- Float finish
- Surface texture produced by a float (wood or magnesium) that leaves a slightly rough, nonslip surface; often used for exterior slabs.
- Stamped concrete
- Decorative finish where patterns are imprinted into plastic concrete using stamps; timing is critical-concrete must be firm enough to hold the imprint.
- Exposed aggregate
- Finish where surface mortar is removed to reveal aggregate; achieved by applying a retarder and washing the surface at the right time.
- Polished concrete
- Surface refined by mechanical grinding with diamond abrasives and chemical densifiers to achieve a glossy, durable finish.
- Self-consolidating concrete
- Highly flowable concrete that spreads under its own weight without vibration; requires high slump flow (24-30 inches) and tight formwork.
- Shrinkage-compensating concrete
- Concrete that expands slightly during curing to offset drying shrinkage, reducing cracking in large flatwork; requires special curing and expansion joints.
- Densifier
- Chemical applied to concrete during polishing to harden the surface and reduce porosity; typically a lithium or sodium silicate solution.
- Release agent
- Powder or liquid applied to stamps or forms to prevent sticking; also used in stamped concrete to prevent stamps from adhering to concrete.
- Flexural strength test
- ASTM C78 test measuring concrete's resistance to bending; important for slab design and often specified for pavements.
- Compressive strength test
- ASTM C39 test on cylindrical specimens to determine concrete strength; typically 28-day strength is specified.
- Air content test
- ASTM C231 pressure meter test to verify air content in fresh concrete; critical for freeze-thaw durability.
- Joint layout
- Plan for contraction and isolation joints to control cracking; keep panels square and avoid re-entrant corners.
- Overlay
- A layer of concrete or other material placed over existing concrete to restore or improve surface; requires proper surface preparation and bonding.
- Curing compound
- Liquid applied to fresh concrete to form a membrane that prevents moisture loss; must comply with ASTM C309.
- Proof-rolling
- Compaction test where a heavy roller is passed over subgrade to identify soft spots; part of subgrade preparation for flatwork.