Concrete Flatwork

Question 1

The term ___ ____ refers to the ground or the base that is directly under and supporting the concrete slab.

Answer 1

Sub-grade

Question 2

Prep if sub grade includes proper levelling and compaction of the soil. T or F

Answer 2

T

Question 3

Problem soils include clay and organic soils. T or F

Answer 3

T

Question 4

What occurs when a slab is on soil which contains both hard and soft spots in close proximity?

Answer 4

Point loading. Causes a bridging effect. Cracks may develop.

Question 5

The ____-____ is a thin layer of granular material that is placed on the prepared sub-grade.

Answer 5

Sub-base.

Question 6

What are some acceptable materials for sub-base?

Answer 6

Crushed stone, gravel, mix of both

Question 7

____ _____ should be placed under all abs where water or water diffusion through the slab may be a problem.

Answer 7

Vapour barriers

Question 8

Vapour barriers also prevents moisture loss from the concrete to the sub-base during curing. T or F

Answer 8

T

Question 9

Vapour barrier would not be used for things like sidewalks or roadways where the barrier is permanently exposed to the exterior. T or F

Answer 9

T

Question 10

Reinforcement should be placed in the ____ portion of the slab and should be supported by small pieces of brick or block. Same with wire mesh.

Answer 10

Lower

Question 11

A minimum design strength of ____ mPa at ____ days is desired for light duty-industrial or institutional and commercial floors.

Answer 11

28 mPa

28 days

Question 12

Slumps of ____ to ____ are the normal range for slab floors.

Answer 12

50 (2”) to 100 (4”)

Question 13

Including _____ ____ improves place ability, reduces surface bleeding and improves resistance to damage cause by freeze/thaw cycles

Answer 13

Entrained-air

Question 14

______ joints may permit both vertical and horizontal movement between two adjacent but separate members.

Answer 14

Isolation

Question 15

The material most commonly used for isolation joints is ____________.

Answer 15

Far-impregnated fibreboard.

Question 16

What is the typical thickness for tar-impregnated fibreboard?

Answer 16

15 mm

Question 17

____ _____ are used to control the location of cracking.

Answer 17

Control

Question 18

A control joint should extend at least ____ and not more than _____ the depth of the slab.

Answer 18

1/4

1/3

Question 19

_____ joints are placed where the concrete pour has been intentionally stopped.

Answer 19

Construction

Question 20

When the concrete is cast directly upon the sub-grade or sub-base without the use of a moisture barrier, what must be done?

Answer 20

The surface should be dampened to reduce the loss of water from the concrete to the sub-base

Question 21

Consolidation by surface vibration is done for slabs up to ____ thick.

Answer 21

200 mm (8”)

Question 22

After consolidation, the final slab height is achieved through _____ or _____.

Answer 22

Screeding or strike-off

Question 23

What is the goal of Screeding?

Answer 23

To remove the top of the placed concrete to the correct height.

Question 24

What is the most important factor in the Screeding and consolidation process?

Answer 24

That it be completed before excess bleed water collects to the surface

Question 25

A long handled ______ is used to eliminate high or low spots left by the the striking off process and to embed large aggregate and bring more fine aggregate and cement paste to the surface.

Answer 25

Bull float

Question 26

When can troweling begin?

Answer 26

After all of the bleed material has evaporated from the surface and the concrete has gained sufficient strength to support an adult.

Question 27

Why must one trowel?

Answer 27

To create a surface that is completely smooth and free of defects.

Question 28

When should the curing process begin?

Answer 28

As soon as possible after troweling is completed.

Question 29

What does the term sub-grade refer to?

Answer 29

The ground or the base that is directly under and supporting the concrete slab.

Question 30

What are the properties of problem soils?

Answer 30

1. Highly expansive or highly compressible.

2. Do not provide uniform support

Question 31

What precautions must be taken when a trench is back filled in a prepared base?

Answer 31

The trench must be back filled with the same material as the surrounding area and the sand degree of compaction.

Question 32

Where is slab thickening used?

Answer 32

Masonry block walls, bearing walls, heavy machinery, exterior walls that support roof loads.

Question 33

What two forces must edge forms be able to resist?

Answer 33

Buckling and downward pressure

Question 34

What type of trowel must not be used on air-entrained concrete?

Answer 34

Steel

Question 35

What are the 3 goals of the curing process?

Answer 35

Protects from rapid drying
Protects from temperature extremes
Protects from damage from use

Question 36

Industrial, civil and commercial job sited often require a floor is:

Answer 36

A) Impermeable to liquids
B) Can sustain point loading from warehouse racking and stationary machinery
C) can withstand moving loads such as forklifts.

Question 37

Over what material should you cast a concrete floor?

Answer 37

Granular material