Site Work, Concrete, and Foundations
This domain tests site preparation, excavation, grading, footings, formwork, reinforcement, concrete placement, and curing. Questions often combine soil bearing, compaction, moisture control, and ACI tolerances.
Core rules and concepts
- Topsoil and unsuitable material are stripped before grading. Structural fill is placed in lifts and compacted to the specified percentage, commonly 95% of maximum dry density. Footings bear on undisturbed or properly compacted soil.
- Formwork must be stable, tight, and properly braced. Rebar needs specified cover, lap lengths, and supports. Before placement, the inspector verifies forms, reinforcement, embedments, and cleanliness.
- Concrete is placed, consolidated, finished, and cured. Air entrainment improves freeze-thaw resistance in Nebraska. Curing typically lasts at least 7 days for normal concrete; cold and hot weather require protection.
- Control joints and construction joints control cracking and separate placements. Slabs need a vapor retarder and granular base where specified.
Worked example
A 20 ft by 30 ft slab is 4 inches thick. Volume = 20 x 30 x 0.333 = 200 cubic feet, or 7.41 cubic yards. With 5% waste, order 7.78 cubic yards. If the slab is placed on a vapor retarder, laps and puncture repairs must be inspected before concrete covers them.
Traps that cost marks
Adding water at the job site to increase slump; forgetting vapor retarder or reinforcement inspection; curing too briefly; placing concrete on frozen subgrade; and confusing control joints with construction joints.
Key point: concrete quality depends on subgrade, reinforcement, water-cement ratio, and curing.