Flashcards

0
Q

Concrete is produced from

A

Portland Cement course and fine aggregates and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

The aggregates used in concrete are

A

Inert mineral ingredients that reduce the amount of cement that would otherwise be needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Aggregate

A

Gravel stone sand or other inert material used in concrete these materials may be fine of course

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Coarse aggregate

A

Gravel or stone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Fine aggregate

A

Sand

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Aggregates make up a

A

Large percentage of the total volume of concrete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Concrete must be Cured in order to reach

A

It’s proper strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Curing fresh concrete requires

A

Correct hydration and temperature control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Improper curing methods will negatively affect

A

The finished surface of the concrete as well as it’s strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Hardening of concrete involves a chemical process known as

A

Hydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

As concrete hardens the gel gives of heat which is known as

A

Heat of hydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Because hydration involves water proper curing requires

A

That the concrete be kept moist until it reaches its desired strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Moist curing of concrete produces

A

A stronger concrete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Concrete can be kept moist by several techniques including

A

Sprinkling it with water, ponding, or covering it with a plastic film

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

In addition to maintaining proper moisture concrete that is curing must be maintained at the correct temperature ideally between

A

50-70 degrees F

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Concrete that is cured at or above 100 degrees Fahrenheit will

A

Not reach its proper strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Concrete cured near freezing temperatures will

A

Harden more slowly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

In massive concrete structures the heat of hydration generated can

A

Adversely affect the final strength of the concrete

18
Q

Concrete can be cooled using

A

Cold water during curing or using chilled water in the mixing process

19
Q

During the curing process Concrete will

A

Shrink slightly

20
Q

Theoretically properly cured concrete continues the to harden indefinitely at a gradual rate however normal design strength is reached

A

After 28 days

21
Q

Different types of concrete Can be produced for specific purposes this is accomplished by varying the ingredients or adding chemicals to the concrete mixture these are generally known as

A

Admixtures

22
Q

The density of concrete can be reduced by using a lighter weight aggregate such as

A

Shale or clinker

23
Q

An admixture known as superplastizer can be used to produce

A

A mixture that flows more freely

24
Coloring can also be added to concrete for
Aesthetic or safety reasons
25
Like masonry concrete is strong in compression but weaker in tension. the ultimate compressive strength can't be varied from
2500 psi to 6000 psi with the allowable stress used in design reduced by a factor of safety
26
In most structural designs tensile forces exist and the concrete must be
Reinforced to resist them
27
The techniques that are used to reinforced concrete are
Ordinary reinforcing Prestressing reinforcing( pretensioning or post tensioning)
28
In ordinary reinforcing when the concrete has hardened it adheres to the reinforcing bars because of
Deformations on the surface of the bars
29
The diameters of standard size reinforcing bars vary from
.375 inches to 2.257 inches
30
Vertical reinforcing bars are known as
Stirrups and are provided to resist the diagonal tension
31
Concrete beams are frequently cast in the shape of a
Tee
32
The wider cross-section area at the top of the Tee beam permits the concrete to
Support a greater load
33
Reinforcing steel is placed in the bottom of the tee to resist
Tensile force
34
Although the primary function of placing reinforcing steel in concrete is to resist tensile forces the steel can also be used to support
Some of the compressive forces
35
More efficient use of concrete is made using a technique known as
Prestressing
36
The prestressing process requires large loads to be applied to the concrete along
The axis of the beam
37
Is widely used in concrete structures
Prestressing
38
Pretensioning. when the steel strands are released the concrete member usually
takes on a slight upward deflection
39
The reinforcing steel used concrete is essential to the strength of
a reinforced concrete member
40
As a general rule reinforcing steel should not be cut in the course of firefighting operations unless
It is necessary to rescue trapped victims
41
The forces that are produced in the prestressing process remain locked in the steel for
The steel for the life of the assembly
42
Cutting through reinforcing steel with a saw or torch is particularly dangerous in
Posttensioned concrete because the steel is not bonded to the concrete