Concrete Final Exam 2023 with complete solution;(Actual
test questions and answers)
Prior to placing concrete for pavements or slabs on grade, what should be done?
Subgrade should be compacted, trimmed, and moistened; forms should be erected; and
the reinforcing steel members should be securely in place.
In hot weather, what is important to do to the subgrade?
It needs to be moistened to prevent the dry ground from sucking water out of the
concrete.
What is true about forms for concrete?
Wood forms should be moistened to prevent water loss from the concrete, all forms
should be able to be removed from the concrete without damaging it. Steel should be
clean and free of rust, steel forms can be below freezing when concrete is poured.
How should concrete be deposited?
Continuously as near as possible to its final position.
How do you deposit concrete on a slab pour?
It should be started along the perimeter at one end of the slab, the concrete should not
be dumped in separate areas and spread out.
How should concrete be placed in walls, thick slabs, or foundations?
In horizontal layers of uniform thickness, each layer should be consolidated before the
next layer is added.
How rapidly should concrete be placed when pouring in layers?
Fast enough to not let the previous layer set.
How is concrete moved to lower elevations?
Chutes and drop chutes are used to prevent segregation of the concrete.
How far can you drop concrete without segregation?
50 feet
What is placed at the end of a chute to control the flow of concrete onto sloped
surfaces?
A baffle
How thick should the layers of freshly mixed concrete be?
6 inches to 20 inches thick for reinforced members, and 15 inches to 20 inches thick for
mass work.
What determines the thickness of a layer of concrete?
Width between forms and the amount of reinforcement.
Should concrete be moved horizontally?
No, this causes segregation. If it has to be done it should be kept to a minimum.
What should be done if pouring concrete in an area where standing water is present?
Concrete should be poured so that the concrete displaces the water ahead of it so it
does not mix.
How is concrete poured into a tall, narrow form?
Through an opening called a window, a hopper is used outside of the opening to control
the flow of the concrete as it enters the form.
How can bleeding be reduced when pouring concrete?
, Pour at a slower rate or by using a concrete of a stiffer consistency, particularly when
pouring the lower part of a form.
How should concrete be poured into deep forms?
To avoid cracks, the concrete placement for around an hour to allow settlement of this
deep member.
When pouring concrete underwater, what should the slump range from, and what is the
maximum W/C ratio?
6 inches to 9 inches, 0.45
What can be done to concrete in order to give it the ability to be poured under water?
Make a mix with high workability, add anti-washout admixtures, use round aggregates,
use a higher percentage of fine aggregate, add entrained air.
When pouring concrete under water, the current of the water should not exceed what
speed?
10 feet per minute
What are the methods for placing concrete underwater?
Tremie, concrete pump, bottom-dump buckets,
grouting preplaced aggregate, toggle bags, bagwork, and
the diving bell.
What is a tremie?
A smooth, straight pipe long enough to
reach the lowest point to be concreted from a working
platform above the water.
What is grouting preplaced aggregate?
Forms are first filled with clean coarse aggregate, then the voids in the coarse
aggregate are filled with a grout to
produce concrete.
What is the consolidation of concrete?
The process of compacting fresh concrete;
to mold it within the forms and around embedded items
and reinforcement; and to eliminate stone pockets, honeycomb, and entrapped air
What are the methods of consolidating concrete?
Mechanical or hand methods, mechanical methods using internal or external vibration
are the preferred methods.
When could you use the hand method to consolidate concrete?
When you have a mix that is workable and flowing.
What are the consequences of the undervibration of concrete?
Honeycombing, excess amount of entrapped air voids (often called bugholes), sand
streaks, cold joints, placement lines, and subsidence cracking.
What are the consequences of the overvibration of concrete?
Segregation resulting from the larger aggregate particles settling and the smaller
aggregates rising, sand streaks, loss of entrained air, form damage, and from failure
caused by pressure from excessive vibration.
What is the curing of concrete?
The maintenance of a satisfactory moisture content
and temperature in concrete for a period of time immediately following placing and
finishing so that the desired properties may develop.
test questions and answers)
Prior to placing concrete for pavements or slabs on grade, what should be done?
Subgrade should be compacted, trimmed, and moistened; forms should be erected; and
the reinforcing steel members should be securely in place.
In hot weather, what is important to do to the subgrade?
It needs to be moistened to prevent the dry ground from sucking water out of the
concrete.
What is true about forms for concrete?
Wood forms should be moistened to prevent water loss from the concrete, all forms
should be able to be removed from the concrete without damaging it. Steel should be
clean and free of rust, steel forms can be below freezing when concrete is poured.
How should concrete be deposited?
Continuously as near as possible to its final position.
How do you deposit concrete on a slab pour?
It should be started along the perimeter at one end of the slab, the concrete should not
be dumped in separate areas and spread out.
How should concrete be placed in walls, thick slabs, or foundations?
In horizontal layers of uniform thickness, each layer should be consolidated before the
next layer is added.
How rapidly should concrete be placed when pouring in layers?
Fast enough to not let the previous layer set.
How is concrete moved to lower elevations?
Chutes and drop chutes are used to prevent segregation of the concrete.
How far can you drop concrete without segregation?
50 feet
What is placed at the end of a chute to control the flow of concrete onto sloped
surfaces?
A baffle
How thick should the layers of freshly mixed concrete be?
6 inches to 20 inches thick for reinforced members, and 15 inches to 20 inches thick for
mass work.
What determines the thickness of a layer of concrete?
Width between forms and the amount of reinforcement.
Should concrete be moved horizontally?
No, this causes segregation. If it has to be done it should be kept to a minimum.
What should be done if pouring concrete in an area where standing water is present?
Concrete should be poured so that the concrete displaces the water ahead of it so it
does not mix.
How is concrete poured into a tall, narrow form?
Through an opening called a window, a hopper is used outside of the opening to control
the flow of the concrete as it enters the form.
How can bleeding be reduced when pouring concrete?
, Pour at a slower rate or by using a concrete of a stiffer consistency, particularly when
pouring the lower part of a form.
How should concrete be poured into deep forms?
To avoid cracks, the concrete placement for around an hour to allow settlement of this
deep member.
When pouring concrete underwater, what should the slump range from, and what is the
maximum W/C ratio?
6 inches to 9 inches, 0.45
What can be done to concrete in order to give it the ability to be poured under water?
Make a mix with high workability, add anti-washout admixtures, use round aggregates,
use a higher percentage of fine aggregate, add entrained air.
When pouring concrete under water, the current of the water should not exceed what
speed?
10 feet per minute
What are the methods for placing concrete underwater?
Tremie, concrete pump, bottom-dump buckets,
grouting preplaced aggregate, toggle bags, bagwork, and
the diving bell.
What is a tremie?
A smooth, straight pipe long enough to
reach the lowest point to be concreted from a working
platform above the water.
What is grouting preplaced aggregate?
Forms are first filled with clean coarse aggregate, then the voids in the coarse
aggregate are filled with a grout to
produce concrete.
What is the consolidation of concrete?
The process of compacting fresh concrete;
to mold it within the forms and around embedded items
and reinforcement; and to eliminate stone pockets, honeycomb, and entrapped air
What are the methods of consolidating concrete?
Mechanical or hand methods, mechanical methods using internal or external vibration
are the preferred methods.
When could you use the hand method to consolidate concrete?
When you have a mix that is workable and flowing.
What are the consequences of the undervibration of concrete?
Honeycombing, excess amount of entrapped air voids (often called bugholes), sand
streaks, cold joints, placement lines, and subsidence cracking.
What are the consequences of the overvibration of concrete?
Segregation resulting from the larger aggregate particles settling and the smaller
aggregates rising, sand streaks, loss of entrained air, form damage, and from failure
caused by pressure from excessive vibration.
What is the curing of concrete?
The maintenance of a satisfactory moisture content
and temperature in concrete for a period of time immediately following placing and
finishing so that the desired properties may develop.
