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carpentry level 2 > G-7 place and finish concrete > Flashcards

G-7 place and finish concrete Flashcards

1
Q

at what stages of finishing is an edger used and why

A

after bull floating , push large aggr away from surface and form and rounds over

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2
Q

why is a divider tool not used to make control joints

A

not deep enough

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2
Q

what is the purpose of hand floating or bull floating

A

push aggregate down

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3
Q

when is the placing of concrete completed

A

after floating

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4
Q

why should the bleed water be allowed to evaporate

A

ruin water cement ratio if not causes dusting or crazing

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5
Q

explain how a broom finish is created

A

floated ,broomed horizontally edged , edged and troweled

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6
Q

when are screeds removed from the concrete

A

after striking off

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7
Q

what is the purpose of a screed

A

guide for striking off

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8
Q

how is the top of concrete wall finished

A

cleats removed and floated

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9
Q

what is the purpose of kneeboards

A

disperse weight

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10
Q

what tool is used to transfer flexible patterns

A

tamper

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11
Q

what are 5 precautions when finishing concrete with a power trowel

A

concrete is flat/level
can bear foot pressure
cover area uniformly
bleed water evaporated
allow concrete to harden between passes

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12
Q

how is the movement of a power trowel controlled

A

push down = right
push up= left

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13
Q

what is a burnished surface

A

mirror like finish
created by steep angled trowels

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14
Q

what are 2 different types of blades for a power trowels

A

float and trowel

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15
Q

what are the environmental concerns associated with concrete treatments

A

streams and ground water

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16
Q

describe how sealers and hardens also act as curing compounds

A

prevents moisture loss

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17
Q

how is a exposed aggregate wall surface created

A

chemicals on forms
then washed off

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18
Q

what is the difference between damp proofing and water proofing

A

moisture resistant
resist hydrostatic pressure

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19
Q

how is a suspended slab water proofed

A

roofing membrane

20
Q

what are pigments used for

A

color

21
Q

what are the 2 required conditions for proper curing

A

moisture /temp

22
Q

what is a favorable temp for placing concrete

A

15-20

23
Q

explain the hydration proccess

A

chemical reaction of water and cement

24
Q

list 4 methods of curing concrete

A

water coat
wet covering
curing compound
mechanical barriers

25
Q

how are chemical hardeners used

A

sprayed or sprinkled

26
Q

why are some curing compounds colored

A

show coverage

27
Q

If 2 coats of curing compound are used , how is the second one applied

A

Perpendicular /90 degrees

28
Q

What is the minimum curing time required to allow the concrete to gain 70% of its 28 day strength

A

3 days

29
Q

What are 2 purposes of chemical sealants

A

Waterproof and improve looks

30
Q

How are powdered hardeners applied to concrete

A

after floating and troweling

31
Q

How is the concrete mixture cooled in hot weather

A

Superplasticizer or cool water

32
Q

What causes “plastic shrinking cracking “

A

Waterloss

33
Q

What is the effect on concrete of using fossil fuel burning heaters and unvented enclosures?

A

Dusting /weak layer of concrete

34
Q

List four problems that can cause a form to fail

A

Poor bracing, poor placement, poor vibrating bad stripping

35
Q

How could vibration cause a form failure?

A

Over vibe equals stress on ties

36
Q

What causes spalling?

A

Stripping before 3 1/2 MPA and bad stripping

37
Q

What is a white crystalline growth on surface of concrete called?

A

EFFlorences

38
Q

How can scaling be prevented

A

Low water, cement ratio, proper placement, quality of concrete

39
Q

Describe the procedure used to place concrete around bucks in a wall form

A

Have we poles, if large have access hole for vibe and place on just one side

40
Q

What is the maximum aggregate size that should be used when repairing con

A

Half the patch size

41
Q

What are the advantages of using premixed grout?

A

Contains chemical bonding agents just add water

42
Q

Why are the edges of the area to be patched sloped inward

A

Tequila patch

43
Q

Why must you wet the area to be patched?

A

Some moisture won’t be sucked out of the patching mix before hydration is complete

44
Q

What service repair situations required using forms

A

Walls and overhead

45
Q

What is the minimum slump of repair concrete?

A

50 mm

46
Q

How long should a patched area be allowed to cure?

A

Three days

47
Q

Explain the sack rubbing process

A

Wet area, rub on stacking dry and let stand rub on dry sacking

carpentry level 2 (11 decks)

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