CNS 220 Exam 2 Questions with Correct Answers Latest Update 2025/2026
What is the ACI and what do they make? - Answers American Concrete Institute, the rule book
for concrete
What kind of water content is in concrete with high strength but it is difficult to work with? -
Answers Lower water content
What kind of water content is in concrete with a lower strength but its easier to work with? -
Answers Higher water content
Why is water the enemy of concrete? - Answers Adding too much can destroy the water to
cement ratio, and freeze/thaw cycles can cause it to crack
What is an ideal water/cement ratio? - Answers 0.5 or less
What can happen to concrete if the water to cement ratio is above 0.5? - Answers Increased
chance of water permeability, a decrease in durability and strength, a decrease in resistance to
sulfate,
What are the steps to obtain quality concrete? - Answers 1. Proper mixing and proportioning
2. Proper transportation and handling
3. Proper placement
4. Proper Finishing
5. Proper curing
How long does concrete last when transporting it? - Answers 90 minutes under normal and cold
weather and 45 minutes under hot weather
How are concrete structures created? - Answers Build formwork, reinforcing, pouring concrete,
finishing and protection
How can concrete be placed? - Answers Chutes, conveyors, buggies, pump trucks, wheelbarrow
and buckets
What does consolidation do in concrete? - Answers Eliminates voids, honeycombs, and air
pockets
What is the point of a concrete vibrator? - Answers Agitates the concrete to make it flow and
eliminate air pockets
What is a possible problem with vibrating concrete? - Answers Too much vibration can cause all
the aggregate to sink, making the concrete weak
, Why is it important to wet down the sub grade before pouring the concrete? - Answers The
grade is dry and it will take the water from the concrete, not allowing it to cure properly
What is an alternative to wetting the sub grade before pouring the concrete? - Answers Laying
down a vapor barrier
What is a common contamination in concrete during the pouring stage? - Answers Rust on the
rebar, dirt from boots walking through wet concrete, and excess oil on the forms
What is the process of finishing concrete? - Answers 1. Screeding
2. Floating
3. Troweling
What is screeding? - Answers The initial leveling and consolidation of concrete
What are some finish options on concrete? - Answers Broom finished, hard troweled, stamped
patterns, exposed aggregate, staining and painting
What is the purpose of curing concrete? - Answers To keep water in the concrete as long as
possible
What are benefits to curing concrete? - Answers Increases strength, decreases permeability and
helps prevent cracking
When does concrete gain most of it's strength? - Answers The first month
How long does hydration occur - Answers Hydration occurs at allowing rate years ofter the
concrete is poured
How can concrete be cured? - Answers With a liquid chemical (Curing compound), Plastic
sheeting laid over the concrete, wet burlap, and flooding the concrete with a dam
How can you protect concrete from freezing while it is curing? - Answers Laying insulated
blankets over it or building a temporary weather enclosure
How can you protect concrete from vandalism while it is curing? - Answers Barricades, warning
signs or watchmen
Why can freezing be a problem when it comes to concrete? - Answers It destroys the strength
and longevity of the concrete
What are some problems with concrete? - Answers Cracking, flaking
What is a continuous footing? - Answers A footing that eventually connects back to itself, a
basement is a good example
What is the ACI and what do they make? - Answers American Concrete Institute, the rule book
for concrete
What kind of water content is in concrete with high strength but it is difficult to work with? -
Answers Lower water content
What kind of water content is in concrete with a lower strength but its easier to work with? -
Answers Higher water content
Why is water the enemy of concrete? - Answers Adding too much can destroy the water to
cement ratio, and freeze/thaw cycles can cause it to crack
What is an ideal water/cement ratio? - Answers 0.5 or less
What can happen to concrete if the water to cement ratio is above 0.5? - Answers Increased
chance of water permeability, a decrease in durability and strength, a decrease in resistance to
sulfate,
What are the steps to obtain quality concrete? - Answers 1. Proper mixing and proportioning
2. Proper transportation and handling
3. Proper placement
4. Proper Finishing
5. Proper curing
How long does concrete last when transporting it? - Answers 90 minutes under normal and cold
weather and 45 minutes under hot weather
How are concrete structures created? - Answers Build formwork, reinforcing, pouring concrete,
finishing and protection
How can concrete be placed? - Answers Chutes, conveyors, buggies, pump trucks, wheelbarrow
and buckets
What does consolidation do in concrete? - Answers Eliminates voids, honeycombs, and air
pockets
What is the point of a concrete vibrator? - Answers Agitates the concrete to make it flow and
eliminate air pockets
What is a possible problem with vibrating concrete? - Answers Too much vibration can cause all
the aggregate to sink, making the concrete weak
, Why is it important to wet down the sub grade before pouring the concrete? - Answers The
grade is dry and it will take the water from the concrete, not allowing it to cure properly
What is an alternative to wetting the sub grade before pouring the concrete? - Answers Laying
down a vapor barrier
What is a common contamination in concrete during the pouring stage? - Answers Rust on the
rebar, dirt from boots walking through wet concrete, and excess oil on the forms
What is the process of finishing concrete? - Answers 1. Screeding
2. Floating
3. Troweling
What is screeding? - Answers The initial leveling and consolidation of concrete
What are some finish options on concrete? - Answers Broom finished, hard troweled, stamped
patterns, exposed aggregate, staining and painting
What is the purpose of curing concrete? - Answers To keep water in the concrete as long as
possible
What are benefits to curing concrete? - Answers Increases strength, decreases permeability and
helps prevent cracking
When does concrete gain most of it's strength? - Answers The first month
How long does hydration occur - Answers Hydration occurs at allowing rate years ofter the
concrete is poured
How can concrete be cured? - Answers With a liquid chemical (Curing compound), Plastic
sheeting laid over the concrete, wet burlap, and flooding the concrete with a dam
How can you protect concrete from freezing while it is curing? - Answers Laying insulated
blankets over it or building a temporary weather enclosure
How can you protect concrete from vandalism while it is curing? - Answers Barricades, warning
signs or watchmen
Why can freezing be a problem when it comes to concrete? - Answers It destroys the strength
and longevity of the concrete
What are some problems with concrete? - Answers Cracking, flaking
What is a continuous footing? - Answers A footing that eventually connects back to itself, a
basement is a good example
