2. Demonstrate Concrete Skills 6831.19

3. Form A wood or metal structure that confines concrete to the desired shape until it hardens

6. Form Trenches are dug in the ground for footings of buildings, and the soil walls are the forms

7. Form Wood or metal can be used

8. Form When wood is used, 2” X 4”, 2” X 6”, 2” X 8” and other 2” size lumber is used because forms must not bend or warp and must be braced to prevent movement

9. Form In warm weather, forms should stay in place 2 to 3 days and twice that long if weather is cold

10. Pour or Place Concrete should be poured or placed as evenly as possible in the forms to prevent having to move it

11. Finishing Bringing the surface of concrete to the proper grade and smoothness

13. Finishing Screeding is using a straightedge such as a 2” X 4” board to level concrete with top of form

15. Finishing Bull float is used to impact the concrete at the surface and to make it easier to finish

17. Finishing Texture of the finishing tool will determine smoothness of concrete surface

18. Finishing Wood float, stiff broom, or burlap will make a gritty, non-slip surface for floors, driveways, or walkways

21. Finishing For a very smooth surface, a steel cement finishing trowel should be used

25. Reinforcement Needed because concrete has low tensile strength and high compressive strength

26. Reinforcement Low tensile strength and high compression strength means it has low stretch and high compaction

27. Reinforcement Helps equalize and prevent cracking or breaking Welded wire is the best reinforcement material

30. Reinforcement Clean steel rods or bars called rebar and clean welded wire are used in concrete for reinforcement

32. Estimating Materials Cubic yards equal length in feet multiplied by width in feet multiplied by thickness in feet divided by 27, which is the number of cubic feet in a cubic yard

33. Estimating Materials Note: thickness of concrete is usually in inches and will need to be changed to a fraction of a foot

34. Estimating Materials Examples: 3’ = ¼ foot, 4” = 1/3 foot, 6” = ½ foot

35. Estimating Materials Example: How many yards of concrete are needed to pour a driveway 100’ long, 8 feet wide, and 3” thick?

36. Estimating Materials Formula: Cu. yds. = 100X8X1/4= 200= 7.41 27 27

37. Estimating Materials Example: If concrete is purchased in only whole yards and 10% should be allowed for waste and uneven ground level, how much ready mixed concrete should be ordered?

38. Estimating Materials 7.41 X 10% = 8.15 To get the right amount, 9 cubic yards must be purchased

39. Treat With Oil Wood and metal forms should be treated with oil and wet down with water before concrete is poured

41. Treat With Oil Oil makes the forms easier to remove and water will prevent swelling

42. Bleeding Water rising to the top surface of concrete poured in tall or deep forms is called bleeding

43. Bleeding This problem can be corrected or reduced by pouring concrete slower and by using a stiffer or less watery mix

44. Demonstrate Concrete Skills 6831.19