Concrete & Inspection

Question 1

Concrete is sometimes used a coating.
True or false?

Answer 1

True

Question 2

Concrete does not require a coating.
True or false?

Answer 2

False, it may require protective coding

Question 3

Concrete is formed with what?

Answer 3

Cement, aggregate and water

Question 4

What are the characteristics of concrete?

Answer 4

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

Question 5

Concrete has how many chemical reactions?

Answer 5

28

Question 6

How is concrete cured?

Answer 6

Cures by hydration

Question 7

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

Answer 7

True

Question 8

Concrete cannot passivate steel. True or false.

Answer 8

False concrete may passivate steel

Question 9

What are some of the different concrete surfaces?

Answer 9

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

Question 10

What is poured (wet cast) concrete?

Answer 10

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

Question 11

What is poured concrete affected by?

Answer 11

Ambient conditions
Vibrations
Finishing operations

Question 12

What are the finishing operations performed on poured concrete?

Answer 12

Troweling
Wood floating
Brooming

Question 13

What are some issues found with poured concrete surfaces?

Answer 13

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

Question 14

What is guniting?

Answer 14

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

Question 15

Preparation of concrete for coating includes what?

Answer 15

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

Question 16

Pre-cleaning of concrete includes the use of what?

Answer 16

Steam cleaning
Chemical cleaning
Detergents

Question 17

Surface preparation of concrete may include what?

Answer 17

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

Question 18

What are some practical considerations and surface preparation of concrete?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

Define acid etching.

Answer 20

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

Question 21

What is most commonly used for acid etching concrete?

Answer 21

Hydrochloric acid known commonly as muriatic acid

Question 22

Define sacking

Answer 22

Consists of rubbing cement mortar over surface with ‘sack’

Question 23

What are precautions to take with sacking?

Answer 23

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

Question 24

What does the socking process include?

Answer 24

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

Question 25

Define stoning

Answer 25

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

Question 26

What is an advantage and disadvantage of steel troweling?

Answer 26

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

Question 27

Cracks and concrete should be repaired. True or false?

Answer 27

True

Question 28

What are the two classifications of cracks in cement?

Answer 28

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

Question 29

Describe bituminous cutback

Answer 29

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

Question 30

Novolac epoxies have excellent chemical resistance. True or false?

Answer 30

True

Question 31

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

Answer 31

False, they bond well to concrete

Question 32

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

Answer 32

True

Question 33

How can you measure the moisture and concrete?

Answer 33

Plastic sheet test (ASTM D 4263) Moisture detector

Question 34

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

Answer 34

A. Potable water

Question 35

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

Answer 35

D. Hydration.

Question 36

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.

Answer 36

C. Greater than 11.5.

Question 37

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

Answer 37

A. Shotcrete application

Question 38

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

Answer 38

B. Chlorinated rubber.

Question 39

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

Answer 39

B. NACE 6/SSPC SP-13

Question 40

What is efflorescence?

Answer 40

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.

Question 41

What is laitance?

Answer 41

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