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Carpentry Level 2 BC 2023 > G4 - Slabs - LT# 1 Slabs-On-Grade > Flashcards

G4 - Slabs - LT# 1 Slabs-On-Grade Flashcards

1
Q

on which kind of surface should a slab-on-grade be placed?

A

1) Suitable bearing
2) Compacted fill

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2
Q

What factors affect the durability of slabs-on-grade?

A

1) Protection from weather
2) Finishing
3) W:C Ratio

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3
Q

What factors affect the strength of slabs-on-grade?

A

1) Base mix 2) Concrete curing 3) Concrete mix

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4
Q

What should be done to walls or columns that pass through or beside slabs-on-grade?

A

Provide Isolation joint

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5
Q

Why is it important to compact the subgrade?

A

To give firm even bearing

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6
Q

Why are screeds and forms oiled before concrete placement?

A

Easy cleaning

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7
Q

How long should slab forms remain in place after concrete placement?

A

As long as possible

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8
Q

What is the minimum slope for drainage for an exterior slab?

A

1/8 per foot (1/96)

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9
Q

What does a give-and-take strip allow for?

A

1)Expansion & contraction
2) Differential movement

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10
Q

Describe pouring a monolithic slab.

A

Monolithic slab - Poured with the perimeter footing and any other slab thickenings at the same time.

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11
Q

What is one setback of pouring a monolithic slab?

A

The footing portion and the floor portion are under different building loads, which may cause stress cracks at these locations.

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12
Q

What is one advantage of a monolithic slab pour?

A

Economical and quick to form and place

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13
Q

Describe pouring an isolated slab on grade.

A

Isolated slab is poured AFTER the walls and footing have been placed.

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14
Q

Where does an isolated slab on grade have an isolation joint?

A

Usually between the slab and footings and an air and moisture barrier between the slab and wall

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15
Q

A slab on grade is only as strong as ______

A

The material it is placed upon

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16
Q

If existing soil (subgrade) is of suitable bearing, it only needs:

A

To be excavated down to a grade and levelled before placing the slab.

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17
Q

If a subgrade is not smooth after grading and leveling, what is laid down?

A

A sub-base, is usually a material that is more uniform in particle size.

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18
Q

If soil is not suitable for a slab on grade, then

A

It must be removed and replaced in compacted lifts with proper granular fill specified in the drawings

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19
Q

What tool is used to provide a firm and even bearing?

A

Plate roller or a ram-type roller

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20
Q

For forming a simple slab which is not too thick, what can be used as formwork?

A

Simple 2x4 to 2x12 depending on the thickness

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21
Q

For thicker edge slab-on-grades, what material is used to form a slab-on-grade?

A

Thicker edge forms, using plywood forms supported by studs and plates may be necessary. Strong backs and braces are used to plumb and straighten.

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22
Q

Controlling the ______ contributes to BOTH the strength and durability

A

Water:Cement ratio

23
Q

In commercial drawings, the slab thickness, strength, and design mix are stated in the drawings by whom?

A

The engineer

24
Q

The slab’s finish, depending on the use of the building, may be specified by whom?

A

The architect

25
Q

The strength of the slab is related to:

A

To the base preparation, compressive strength of the concrete mix, and proper curing.

26
Q

Rebar, admixtures specified by the engineer contribute to what?

A

The strength of the slab

27
Q

In residential construction, where can most compressive strength information can be cited where?

A

BCBC

27
Q

In residential construction, where can most compressive strength information can be cited where?

A

BCBC

28
Q

A mat of rebar is placed in the lower portion of the slab to protect it from:

A

Tensile forces

29
Q

The durability of a slab on grade is based on its:

A

1) Compressive strength (expressed in MPA) (Megapascals)

2) Admixtures added

3) Treatment after placing

30
Q

Industrial buildings require treatments why?

A

To increase durability against continuous traffic and heavy load

31
Q

For interior slabs, admixtures are sometimes added to the mix to protect from?

A

Chemicals, oils and greases

32
Q

What can be added to harden the surface of a floor in a high-traffic area?

A

Powered or mechanical hardeners can be applied to the surface of the slab during finishing

33
Q

What is specified for all exterior concrete exposed to free-thaw cycles?

A

Air entrainment adds microscopic air bubbles to the concrete, it allows it to expand and contract without great risk of damage

34
Q

Does BCBC require reinforcement for slabs on grade?

A

No, many basement and garage floor slabs are not reinforced

35
Q

What forms can reinforcement take form in a slab on grade?

A

Heavy wire mesh, or grid of rebar

36
Q

For concrete in contact with te ground, rebar should be kept how far off the bottom of the slab?

A

3 “ (75 mm)

with good drainage below the slab and a polyethylene ground cover, the rebar may be as close as 30 mm to the bottom of the slab

37
Q

With good drainage below the slab, and a polyethylene ground cover, the reinforcement can be as close as:

A

30 mm to the bottom of the slab

38
Q

When attaching reinforcement on the bottom of a slab in contact with the ground, what techniques are used?

A

Chairs, bricks, and rocks are used to support the rebar to the proper height. Also a special hook tool.

39
Q

The surface of an exterior slab-on grade should be sloped how much per foot for drainage?

A

1/8” per foot (1:96)

40
Q

Interior floor slabs are required by BCBC to:

A

Have the bottom of the slab above the top of the perimeter drain pipe

41
Q

Elevations for slab can be set how?

A

Using screed boards or pipe with screed stakes.

42
Q

Where a slab meets a foundation wall, what is required?

A

A bond break in the form of an isolation joint. Preventing differential settlement.

43
Q

Additional expansion joints should be placed in slabs at least every

A

15 m (50’) known as give-and-take strips,

44
Q

What is the purpose of a give-and-take strip?

A

Used to isolate one concrete member from another and allow vertical and horizontal movement

45
Q

Give-and-take strips are made from

A

Asphalt-impregnated fibreboard

46
Q

What is a control joint?

A

A weakening in the concrete slab that is designed to control the natural cracking of a concrete member due to shrinkage

47
Q

The spacing of control joints for driveways and garage floors may be spaced

A

As close as 3 m (10’) apart

48
Q

Expansion joints may be spaced no farther than:

A

15 m apart

49
Q

How is a control joint made?

A

Tooled, cut in or formed by a two-part T-shaped plastic strip called a zip strip.

50
Q

How deep does a control joint need to be to be effective?

A

At least one-quarter the thickness of the slab

51
Q

What does a polyethylene barrier at the sub-base of the slab-on-grade do?

A

Keeps moisture from migrating into the concrete from below, or keeps soil gases from entering the building, or both.

52
Q

How does a high-rise get it’s concrete?

A

Crane with a bucket

53
Q

How are gutters and curbs formed?

A

Hand-set the forms using planks and plywood or have a curb forming machine “slip-form” them

Carpentry Level 2 BC 2023 (50 decks)

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