Concrete & Inspection Flashcards
Concrete is sometimes used a coating.
True or false?
True
Concrete does not require a coating.
True or false?
False, it may require protective coding
Concrete is formed with what?
Cement, aggregate and water
What are the characteristics of concrete?
Extremely durable
Inorganic
Hard
Has good compressive strength
Improves with age (hardens overtime)
Concrete has how many chemical reactions?
28
How is concrete cured?
Cures by hydration
Concrete pH may be as high as 13. True or false?
True
Concrete cannot passivate steel. True or false.
False concrete may passivate steel
What are some of the different concrete surfaces?
Poured
Concrete block
Special concrete surfaces, such as shotcrete, asbestos, glass fiber products
What is poured (wet cast) concrete?
Wet cast concrete is poured with the high water content to allow concrete to flow into form
What is poured concrete affected by?
Ambient conditions
Vibrations
Finishing operations
What are the finishing operations performed on poured concrete?
Troweling
Wood floating
Brooming
What are some issues found with poured concrete surfaces?
Pinholes
Rock and air pockets
Tie holes from tie wires
Offsets at junctions
What is guniting?
The process of spraying or slinging shotcrete onto a surface at thicknesses up to 10 inches inches
Preparation of concrete for coating includes what?
Pre-cleaning
Surface preparation
Surfaces/filling voids (most difficult)
Pre-cleaning of concrete includes the use of what?
Steam cleaning
Chemical cleaning
Detergents
Surface preparation of concrete may include what?
Abrasive blast cleaning
Hand and power tool cleaning
High-pressure waterjetting or blasting
Acid etching
Stoning
Centrifugal blasting
Scarifying
What are some practical considerations and surface preparation of concrete?
Hold the blast nozzle further from the work
Use lower pressure
Move blast nozzle quickly over the work
Use a finer size abrasive
What are some advantages of waterjetting and wet abrasive blast cleaning of concrete?
Fast cutting of the surface
Washing dust away
Reducing abrasive and concrete particles in the air
Define acid etching.
Acid etching (ASTM D 4260) uses dilute acid to remove laitance and roughen in the surface
What is most commonly used for acid etching concrete?
Hydrochloric acid known commonly as muriatic acid
Define sacking
Consists of rubbing cement mortar over surface with ‘sack’
What are precautions to take with sacking?
Correct, mixing of the mortar
Sins and projections removed before sacking
Proper cure time
What does the socking process include?
Wedding in the substrate with water
Applying water
Rubbing the mortar over surface
Redoing surface to remove access mortar
Define stoning
Stoning is similar to sucking, except that abrasive block is used instead of a sack
What is an advantage and disadvantage of steel troweling?
Smooth surface and fills holes and pores
May yield surface to smooth for coating
Cracks and concrete should be repaired.
True or false?
True
What are the two classifications of cracks in cement?
Active (self made, and subject to movement)
Static (do not move)
Describe bituminous cutback
Solvent solutions of coal tar or asphalt
Maybe applied alone or as buildup membranes with glass fiber
Waterproofing materials
Novolac epoxies have excellent chemical resistance.
True or false?
True
Novolac epoxies do not bond well to concrete. True or false?
False, they bond well to concrete
Elastomeric polyurethanes are usually 100% solids in our applied by poly component spray. True or false?
True
How can you measure the moisture and concrete?
Plastic sheet test (ASTM D 4263)
Moisture detector
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. Potable water
Concrete cures by what process?
A. Oxidation.
B. Reaction with carbon dioxide.
C. Solvent evaporation.
D. Hydration.
D. Hydration.
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.
C. Greater than 11.5.
The term gunite refers to:
A. Shotcrete application
B. Water blasting
C. Abrasive blasting
D. Broom finish
A. Shotcrete application
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
B. Chlorinated rubber.
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
B. NACE 6/SSPC SP-13
What is efflorescence?
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.
What is laitance?
Weak surface layer of water, rich cement mixture on the surface of fresh concrete caused by the upward movement of water
