Concrete & Inspection Flashcards

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1
Q

Concrete is sometimes used a coating.
True or false?

A

True

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2
Q

Concrete does not require a coating.
True or false?

A

False, it may require protective coding

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3
Q

Concrete is formed with what?

A

Cement, aggregate and water

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4
Q

What are the characteristics of concrete?

A

Extremely durable
Inorganic
Hard
Has good compressive strength
Improves with age (hardens overtime)

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5
Q

Concrete has how many chemical reactions?

A

28

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6
Q

How is concrete cured?

A

Cures by hydration

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7
Q

Concrete pH may be as high as 13. True or false?

A

True

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8
Q

Concrete cannot passivate steel. True or false.

A

False concrete may passivate steel

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9
Q

What are some of the different concrete surfaces?

A

Poured
Concrete block
Special concrete surfaces, such as shotcrete, asbestos, glass fiber products

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10
Q

What is poured (wet cast) concrete?

A

Wet cast concrete is poured with the high water content to allow concrete to flow into form

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11
Q

What is poured concrete affected by?

A

Ambient conditions
Vibrations
Finishing operations

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12
Q

What are the finishing operations performed on poured concrete?

A

Troweling
Wood floating
Brooming

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13
Q

What are some issues found with poured concrete surfaces?

A

Pinholes
Rock and air pockets
Tie holes from tie wires
Offsets at junctions

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14
Q

What is guniting?

A

The process of spraying or slinging shotcrete onto a surface at thicknesses up to 10 inches inches

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15
Q

Preparation of concrete for coating includes what?

A

Pre-cleaning
Surface preparation
Surfaces/filling voids (most difficult)

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16
Q

Pre-cleaning of concrete includes the use of what?

A

Steam cleaning
Chemical cleaning
Detergents

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17
Q

Surface preparation of concrete may include what?

A

Abrasive blast cleaning
Hand and power tool cleaning
High-pressure waterjetting or blasting
Acid etching
Stoning
Centrifugal blasting
Scarifying

18
Q

What are some practical considerations and surface preparation of concrete?

A

Hold the blast nozzle further from the work
Use lower pressure
Move blast nozzle quickly over the work
Use a finer size abrasive

19
Q

What are some advantages of waterjetting and wet abrasive blast cleaning of concrete?

A

Fast cutting of the surface
Washing dust away
Reducing abrasive and concrete particles in the air

20
Q

Define acid etching.

A

Acid etching (ASTM D 4260) uses dilute acid to remove laitance and roughen in the surface

21
Q

What is most commonly used for acid etching concrete?

A

Hydrochloric acid known commonly as muriatic acid

22
Q

Define sacking

A

Consists of rubbing cement mortar over surface with ‘sack’

23
Q

What are precautions to take with sacking?

A

Correct, mixing of the mortar
Sins and projections removed before sacking
Proper cure time

24
Q

What does the socking process include?

A

Wedding in the substrate with water
Applying water
Rubbing the mortar over surface
Redoing surface to remove access mortar

25
Q

Define stoning

A

Stoning is similar to sucking, except that abrasive block is used instead of a sack

26
Q

What is an advantage and disadvantage of steel troweling?

A

Smooth surface and fills holes and pores
May yield surface to smooth for coating

27
Q

Cracks and concrete should be repaired.
True or false?

A

True

28
Q

What are the two classifications of cracks in cement?

A

Active (self made, and subject to movement)
Static (do not move)

29
Q

Describe bituminous cutback

A

Solvent solutions of coal tar or asphalt
Maybe applied alone or as buildup membranes with glass fiber
Waterproofing materials

30
Q

Novolac epoxies have excellent chemical resistance.
True or false?

A

True

31
Q

Novolac epoxies do not bond well to concrete. True or false?

A

False, they bond well to concrete

32
Q

Elastomeric polyurethanes are usually 100% solids in our applied by poly component spray. True or false?

A

True

33
Q

How can you measure the moisture and concrete?

A

Plastic sheet test (ASTM D 4263)
Moisture detector

34
Q

Cement mortar coatings have prevented reinforcing steel from corroding when subjected to what solution?
A. Potable water
B. Distilled water
C. Acid
D. Surfactants

A

A. Potable water

35
Q

Concrete cures by what process?
A. Oxidation.
B. Reaction with carbon dioxide.
C. Solvent evaporation.
D. Hydration.

A

D. Hydration.

36
Q

Many grades of steel are passivated by concrete when the pH of concrete reaches ______.
A. Seven or neutral.
B. Less than six.
C. Greater than 11.5.
D. Six211.5.

A

C. Greater than 11.5.

37
Q

The term gunite refers to:
A. Shotcrete application
B. Water blasting
C. Abrasive blasting
D. Broom finish

A

A. Shotcrete application

38
Q

Which type of coating has a long history of successful application and use in swimming pools?
A. Novolac epoxy
B. Chlorinated rubber
C. Bituminous cutback
D. Coal tar epoxy

A

B. Chlorinated rubber.

39
Q

What does a joint abrasive blasting standard for the surface preparation of concrete?
A. NACE 9/SSPC SP-17
B. NACE 6/SSPC SP-13
C. NACE 4/SSPS SP-7
D. NACE 7/SSPS SP-16

A

B. NACE 6/SSPC SP-13

40
Q

What is efflorescence?

A

This condition is caused by moisture, passing through the concrete and carrying a soluble concrete salts with it to the surface. The salt react with carbon dioxide in the atmosphere creating a fluffy white crystal line deposit on the surface.

41
Q

What is laitance?

A

Weak surface layer of water, rich cement mixture on the surface of fresh concrete caused by the upward movement of water