Concrete Flatwork Construction Techniques

1. Chapter 4 Flatwork Ground-Supported Slabs • Exterior Flatwork

2. Rigid insulation extends 24 horizontally or vertically from the perimeter of a slab‑on‑grade foundation. The top surface of the slab is a minimum of 8 above the outside grade level.

3. The building site for a slab‑on‑grade floor must be excavated to undisturbed soil. Compacted fill, a gravel base course, and a vapor barrier are placed in the excavation.

4. Bulkheads are used to form construction joints when a concrete slab is placed in sections. Premolded key strips or metal dowels are permanently embedded in the slab.

5. Concrete is placed in sections for large industrial or commercial concrete slabs.

6. A screed system is used to strike off concrete placed for a concrete floor slab. The screed is supported by wood stakes or adjustable metal supports.

7. Metal pipe screeds are used to support a strike board.

8. Control joints in a concrete slab confine cracking resulting from expansion and contraction of the slab. Control joints are hand tooled or cut into the slab.

9. An expansion joint is used when a great amount of expansion and contraction is anticipated.

10. An expansion joint contains caulking or a preformed asphalt‑impregnated strip.

11. Welded wire reinforcement is used to reinforce concrete floor slabs.

12. To ensure maximum strength of concrete welded wire reinforcement must be set no more than 2 from the top surface of the concrete, or in the middle of the slab.

13. Rebar is held in place using chairs and is tied together using wire ties. Protective coatings are used to decrease corrosion.

14. Fibers in concrete reduce cracking caused by drying shrinkage and thermal expansion.

15. The section view of a print provides information regarding the location, thickness, and reinforcement of the basement floor slab.

16. Screeds are set up close to the foundation walls when concrete is placed for a basement floor slab.

17. Garage floors are sloped 1/8 to 1/4 per foot toward the front of the garage. The garage floor is formed on three sides by the foundation walls and on one side by a form board.

18. Exterior flatwork includes driveways, walkways, and patios. Expansion and control joints are used to control cracking.

19. The finished surface of the garage or carport end of a driveway should be 1/2 below the surface of the garage floor. The driveway is sloped away from the garage to facilitate drainage.

20. A concrete trough with a removable grate diverts water away from a garage that has a driveway sloping toward the garage.

21. Two edge forms are required to form a driveway. The garage floor and sidewalk are used to form the concrete on both ends.

22. 2 x 4 or 2 x 6 form boards are used to form the sides of walks. A public sidewalk and building stoop are used to form the concrete on both ends.

23. Curved forms may be required to form curves for sidewalks or driveways. The example is a 5‑0 wide sidewalk with a 15‑0 radius.

24. Plywood is used to form curves. Saw kerfs are made in 3/4 plywood to provide greater flexibility.

25. Patios serve as outdoor recreational areas in residential construction. Wood dividers add to the attractiveness of the patio and serve as screeds to strike off the patio.

26. Job‑built or prefabricated curb and gutter forms are used to form curbs and gutters. The top of the curb is usually flush with the sidewalk surface and the top of the gutter is flush with surface of the roadway.

27. Tendons are placed in the slab area before the concrete is placed. After the concrete has hardened, the tendons are stressed with hydraulic jacks and held in place with anchoring devices.