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Carpentry Level 2 > G7 > Flashcards

G7 Flashcards

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1
Q

what is a main powdered hardener?

A

Sodium Silicate, sprinkled over concrete and bull floated in reacting with the lime creating a hard dust-proof surface

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2
Q

how fast should you place the concrete after the water has been added?

A

120 minutes

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3
Q

what is and edger?

A

used too round the outside corners of the surface of the slab, and create a decretive boarder

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4
Q

what is spalling around rustication strips? (keyways)

A

larger bits or chunks of concrete stuck too the strip and pulled off

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5
Q

how far apart, and how far down does the pencil vibrator get placed when vibrating concrete walls?

A

not more than 600mm apart and 150mm into the previous layer

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6
Q

What does a bull float do?

A

used too push larger aggregates under the surface and level and smoothen large slabs

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7
Q

what does spalling mean?

A

Spalling is similar to scaling except large chunks instead of just flakes break loose

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8
Q

how long should the area being patched stay wet for?

A

2 hours prior to patching

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9
Q

what does dusting mean?

A

fine loose powder caused by the deterioration of a weak surface.

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10
Q

what happens when dry shrinkage occurs?

A

shrinkage happens mostly because of the reduction of capillary water by evaporation and the water in the cement paste. Tensile stress increases causing stress cracks

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11
Q

what is honeycombing?

A

trapped air bubbles from improper vibration that is visible after forms are removed

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12
Q

what is placed just before the patch goes on?

A

a bonding agent

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13
Q

what are concrete buckets used for?

A

moving concrete on tall buildings hoisted by a crane

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14
Q

what is curing?

A

to keep concrete moist as long as possible for maximum strength growth

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15
Q

what is a groover?

A

like a hand divider tool but larger with a long handle for making grooves in slabs

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16
Q

why should the edges of the area being patch be sloped inward?

A

to create more surface and bonding area for the patch

17
Q

what is Efflorescence?

A

As water from the interior of the concrete migrates to the surface and evaporates, salts are deposited on the surface, usually as a white stain

18
Q

what does segregation mean?

A

excessive vibration causing the course course aggregates to settle to the bottom.

19
Q

what should the slump of a concrete patch be?

A

no less than 50mm

20
Q

what does it mean too continually pour concrete within multiple forms or slabs?

A

Monolithic concrete placement

21
Q

how far apart are external vibrators placed?

A

1200mm apart

22
Q

what is bleed water?

A

excess water in the concrete mixture that is not needed for the chemical reaction with the cement. the bleed water will rise too the surface and evaporate.

23
Q

what does crazing mean?

A

minute cracking of the concrete surface caused by bleed water not fully evaporated disrupting the water/cement ratio

24
Q

what is a screed/strike off bar and what does it do?

A

long 2X4 the extends beyond the edge of a slab for to level out the concrete

25
Q

What happens when concrete flash sets?

A

concrete hardens too quickly resulting in improper finishing and inadequate strength

26
Q

What is the capacity of a concrete bucket?

A

Depends on the lifting capacity of the crane, usually able too care between 0.4 - 1.5m cubed

27
Q

what does flaking mean?

A

very thin flakes of concrete separating from the surface

28
Q

What is the soul purpose of vibration?

A

To remove pockets of air from the concrete

29
Q

what is the difference between a divider and a control joint tool?

A

a divider is only for decorative purposes where a control joint tool has a deeper cutter for creating control joints

30
Q

what are 2 ways to keep concrete moist for an extended period of time?

A

spray-on acrylic curing liquid or plastic sheets

31
Q

what is the minimum temperature for curing?

A

10 degrees celsius

32
Q

what is the minimum and maximum slope of a walkway

A

2% to 8%

33
Q

what is sack-rubbing finish mean?

A

concrete low spots can be filled with the use of a flowable sacking mix mortar and burlap pads. fills voids in the concrete and left flush with surrounding surfaces.

34
Q

Concrete is placed in lifts because why?

A

so that the overall height of the fresh concrete does not exceed the rate of placement set by the form design

35
Q

concrete that has only been cured for 0 days, 3 days, or 7 days will only have which percent strength?

A

50%, 70%, 90% of it 28 day strength

Carpentry Level 2 (9 decks)

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