1. Carry Out Concreting to Simple Forms
BCGCO2003B

2. Introduction
Concreting is a commonly used task in the Building Construction Industry.
As a plumber you will probably not be expected to do a large area of concrete.
For this you are generally better off engaging the services of an experienced concreter.

3. Common Concreting Tasks for Plumbers
Plumbers often have to:-
Repair paths after cutting to make way for water or drainage pipes.
Repair slabs around penetrations or boxed out areas for baths or shower traps.
Form concrete mounds around wastes and drains at ground level. E.g. Disconnector gullies.
Form and pour drainage pits.
Make repairs to masonry walls around pipes.

4. Basics
Even for these simple tasks, it will help to understand the basics of concrete.
Such as:-
What is concrete made of.
Effects of too much water.
Methods of mixing/delivering.
Process of forming, screeding and finishing.

5. Making Concrete
Generally a reasonable mix would be made from the following;-
4 parts aggregate
2 parts sand
1 part cement
Enough water to make mix workable.
(Depends on moisture content in sand)

6. Aggregate
Crushed stone or 'metal', the most commonly used size being 20 mm.
Usually basalt, granite or dolomite and must be clean with no clay or dirt included.

7. Sand
The preferred sand for concrete is clean (washed) and sharp.

8. Cement For general use the Portland type A cement is recommended.
It now comes in 20kg bags

9. Portable mixer
Used mainly by brickies but suitable for small tasks or repairs in conjunction with wheelbarrows.

10. Mixing by Hand
Measure the components by volume using a container such as a bucket.
Using a shovel is not recommended for measuring ingredients.
A heaped shovel of damp sand has a greater volume than the average shovel-load of cement or gravel.

11. Best Option
Concrete trucks delivering directly to area via chutes.

12. Wheelbarrows
Suitable for small quantities and short distance pouring.

13. Time is Money
Using a minimum of two barrows ensures less waiting time for driver.

14. Concrete Pumps
Pumps become economical to use for large volumes or hard to get to places.

15. Concrete Pumps
Pouring directly from chute into hopper on pump.

16. Finished Levels
Levels should be calculated using laser or Dumpy levels prior to concrete arriving.
Keep in mind some surfaces need to be self draining and not completely level.
Small off-cuts of reinforcing are often used as markers for levels. These may be removed as levels are achieved.

17. Concrete Vibrators
Used to ensure maximum compaction and subsequent strength of concrete.

18. Rough Levelling
This is achieved most effectively by placing slightly more concrete than required all over.
Follow this by dragging a square mouth shovel across the surface towards yourself.
Make sure the level is still slightly higher than final level required.)

19. Screeding
A straight edge is used alternatively in a chopping and a sawing action to move the concrete along to one end.

20. Finishing Finishing consists of three processes:- Floating Trowelling
Edging & Joints

21. Floating
Trowelling is required to leave a dense, hard, smooth and durable surface.
The first step in this process is called floating.
After floating the concrete
should be left to set
before the final trowelling

22. Trowelling
When the concrete is firm enough to stand on leaving few markings, the final trowelling may begin.
This may be done by
hand or a high quality
job will be achieved
with a power float.

23. Edging All edges should be done Neater and stronger edge
Less prone to chipping

24. Joints Every concrete slab above 2.4 by 2.4 metres should have joints
Joints are to prevent cracking
They allow the concrete to move
There are two types of joints in concrete slabs, Expansion Joints and Controlled Crack Joints

25. Expansion Joints
They may be also called construction or isolation joints.
They provide space between concrete slabs to allow for expansion on hot days and compression in cold days.
Usually these Joints are installed during the initial installation of the concrete.
Most are made of wood or some soft material so they can move with the expansion and compression of the concrete.

26. Control Joints Control joints are made during finishing.
Usually these Joints are cut into the slab after the concrete hardens.
A slab without crack joints will crack in random patterns and will reduce the life of the concrete slab.

27. Curing Means to cover the concrete so it stays moist while it hardens.
Do it as soon as the surface will not be damaged by the sheeting touching it.
The concrete will last longer, be stronger and less likely to crack.
Sometimes the application of a fine water mist is required.

28. Show Concrete Video

29. Student Response Sheet
1. List 3 likely concreting tasks a plumber may undertake.
(a) Path or slab repairs (b) Concrete mounds
(c) Forming & pouring pits
2. What 2 items may be used to protect a person from coming into direct contact with concrete or cement.
(a) Gloves (b) Barrier cream
3. Concrete is made by mixing:
(a) Water (b) Cement
(c) Coarse & Fine aggregates (d) Admixtures
4. The most common type of cement is:
General purpose Portland cement Type A (GP)

30. a) Strong b) Hard c) Durable
5. Aggregates should be:
a) Strong b) Hard c) Durable
d) Chemically inactive (e) Clean (f) Graded
6. Cement should be stored in a well aired, clean, dry place off the ground.
7. Rounded aggregates give a more workable mix
Angular aggregates make concrete Harder to place, work and compact but can make concrete stronger.
Water must be Clean, fresh and free from any dirt, unwanted chemicals or rubbish that may affect concrete
8. What are the three states that concrete goes through?
1. Plastic 2. Setting 3. Hardening
9. The most important properties of plastic concrete are?
Workability & cohesiveness .

31. 10. Workability means how easy it is to?
a) Handle b) Place c) Compact
d) Finish
11. Never try to make a mixture more workable by adding water because this lowers the strength and durability
12. Cohesiveness is how well concrete holds together
13. Well made concrete – a naturally durable and strong material. It is:
a) Dense
b) Reasonably watertight
c) Resists Temperature changes
d) Resists weathering

32. 14. How is strength measured?
With the compression test
15. Compaction is removing air from the concrete
16. Curing is keeping the concrete damp for a period to allow it to reach maximum strength
17. What does the slump test show?
Workability
18. What does the compression test show?
The best possible strength concrete can reach in perfect conditions

33. 19. When ordering ready-mixed concrete you will need
19. When ordering ready-mixed concrete you will need to tell the supplier:-
a) Name and address for delivery
b) What the concrete is for, e.g. driveway, footing. et
c) Amount (M3)
d) Strength in MPa. (e.g. 20, 25……..)
e) Slump (mm)
f) Maximum aggregate size (e.g. 20mm)
g) Access -how you want to place the concrete (Pump/barrow/directly from chute)
h) Time of first truckload
i) Time between truckloads
j) Any admixtures (normally left to pre-mix concrete company)
k) Always order more e.g. 10% for wastage etc.

34. 20. If the cement content is increased, what else will increase
a) Strength
b) Durability
21. If the water content is increased, what will be the outcome?
Weaker strength concrete
22. What does formwork do?
Gives concrete its shape
23. What does reinforcement do?
Increases strength and helps control cracking

35. 24. Segregation makes the concrete:
a) Weaker
b) Less durable
c) Poor surface finish
25a) How can segregation be avoided?
Check concrete is not too dry or too wet.
b) What is compaction?
The shaking or vibrating of concrete to remove air.
26. It is worse to under vibrate than to over vibrate.
27. What are the two finishing stages?
a) Initial (screeding with or without bullfloating)
b) Final (Floating,Trowelling, edging joints, patterns)

36. 28. What are the two stages in floating? a) BullFloat
b) Power or handfloat
29. When can the final finishing be carried out?
Once any bleed water dries up and the concrete can support a person’s weight leaving only slight marking.
30. Edging and grooving is done to?
Give a neater, stronger edge less prone to chipping.
What is curing?
Making sure the concrete stays moist while hardening. Often by being covered.
32. Why do you cure concrete?
a) Less likely to crack b) More durable
c) Stronger

37. 33. What is the minimum time for curing concrete?
House hold job – 3 days
More strength & durability – 7 days
34. The longer concrete is cured, the closer it will be to its best possible strength and durability.
35. What is a control joint?
A groove of 1/4 -1/3 the depth of the concrete creating a line of weakness in the slab. As concrete shrinks it will crack below this line.
36. There are two types of reinforcement, what are they?
a) Mesh Sheets
b) Loose bars c) Polypropylene fibres

38. 37. Formwork must be?
a) Accurate
b) Strong
c) Well made
38. How much concrete do you need to repair a path 900mm wide by 2 metres long and 75mm thick. Remember to add a 10% allowance.
V = L x W x H
= 2 x .9 x .075
= % of .135 = .0135
= .15 m3
In this case the minimum order would be .2 m3 anyway.

39. 39. How much extra concrete should generally be ordered
39. How much extra concrete should generally be ordered to cover wastage?
10%

40. The Practical Task

41. Basic concrete

42. Make sure forms are square and fixed firmly.

43. Place formwork on a bed of sand so that moisture from concrete has somewhere to go.

44. The formwork should be treated with a releasing agent to ensure it comes away from the concrete when set.

45. Sand under the concrete must be well compacted

46. A gauge cut to the required concrete thickness should be used to ensure an even thickness of concrete.

47. Compact the sand well and remove any excess

48. Use the straight-edge to screed the concrete

49. Pay particular attention to edges and corners as this is where honeycombing may occur.

50. A slump test is done to check the consistency of your mix.
A dampened, cylindrical cone is placed on a non-porous surface & filled with concrete in three even stages

51. Each stage should be vibrated (prodded 25 times) to expel excess air.
The base of the cone needs to be held down to prevent concrete squeezing out underneath.

52. The prodding should be done all the way through the concrete.

53. Lift cone straight off, do not jiggle, allow concrete to slump

54. Place cone, upside down, next to slumped concrete,
Lay rod across the base and measure down to the highest point of the slump.

55. Do not work (trowel /float) the concrete while it is too wet, usually this should be left until excess water has gone off the surface.

56. Edging-tool should be held as flat and square as possible
Formwork should be cleaned and edging-tool run through to push stones in from the sides to allow a smoother finish
Edging-tool should be held as flat and square as possible

57. Make sure you edge right into the corners.

58. When concrete is firm enough, a flat-trowel finish is non-slippery yet finer than a float finish.

59. Da-Daa

60. Clean around your work area and clean and put away all tools, straight-edges and equipment.