Flashcards

Question 0

Concrete is produced from

Answer 0

Portland Cement course and fine aggregates and water

Question 1

The aggregates used in concrete are

Answer 1

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

Question 2

Aggregate

Answer 2

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

Question 3

Coarse aggregate

Answer 3

Gravel or stone

Question 4

Fine aggregate

Answer 4

Sand

Question 5

Aggregates make up a

Answer 5

Large percentage of the total volume of concrete

Question 6

Concrete must be Cured in order to reach

Answer 6

It’s proper strength

Question 7

Curing fresh concrete requires

Answer 7

Correct hydration and temperature control

Question 8

Improper curing methods will negatively affect

Answer 8

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

Question 9

Hardening of concrete involves a chemical process known as

Answer 9

Hydration

Question 10

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

Answer 10

Heat of hydration

Question 11

Because hydration involves water proper curing requires

Answer 11

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

Question 12

Moist curing of concrete produces

Answer 12

A stronger concrete

Question 13

Concrete can be kept moist by several techniques including

Answer 13

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

Question 14

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

Answer 14

50-70 degrees F

Question 15

Concrete that is cured at or above 100 degrees Fahrenheit will

Answer 15

Not reach its proper strength

Question 16

Concrete cured near freezing temperatures will

Answer 16

Harden more slowly

Question 17

In massive concrete structures the heat of hydration generated can

Answer 17

Adversely affect the final strength of the concrete

Question 18

Concrete can be cooled using

Answer 18

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

Question 19

During the curing process Concrete will

Answer 19

Shrink slightly

Question 20

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

Answer 20

After 28 days

Question 21

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

Answer 21

Admixtures

Question 22

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

Answer 22

Shale or clinker

Question 23

An admixture known as superplastizer can be used to produce

Answer 23

A mixture that flows more freely

Question 24

Coloring can also be added to concrete for

Answer 24

Aesthetic or safety reasons

Question 25

Like masonry concrete is strong in compression but weaker in tension. the ultimate compressive strength can’t be varied from

Answer 25

2500 psi to 6000 psi with the allowable stress used in design reduced by a factor of safety

Question 26

In most structural designs tensile forces exist and the concrete must be

Answer 26

Reinforced to resist them

Question 27

The techniques that are used to reinforced concrete are

Answer 27

Ordinary reinforcing

Prestressing reinforcing( pretensioning or post tensioning)

Question 28

In ordinary reinforcing when the concrete has hardened it adheres to the reinforcing bars because of

Answer 28

Deformations on the surface of the bars

Question 29

The diameters of standard size reinforcing bars vary from

Answer 29

.375 inches to 2.257 inches

Question 30

Vertical reinforcing bars are known as

Answer 30

Stirrups and are provided to resist the diagonal tension

Question 31

Concrete beams are frequently cast in the shape of a

Answer 31

Tee

Question 32

The wider cross-section area at the top of the Tee beam permits the concrete to

Answer 32

Support a greater load

Question 33

Reinforcing steel is placed in the bottom of the tee to resist

Answer 33

Tensile force

Question 34

Although the primary function of placing reinforcing steel in concrete is to resist tensile forces the steel can also be used to support

Answer 34

Some of the compressive forces

Question 35

More efficient use of concrete is made using a technique known as

Answer 35

Prestressing

Question 36

The prestressing process requires large loads to be applied to the concrete along

Answer 36

The axis of the beam

Question 37

Is widely used in concrete structures

Answer 37

Prestressing

Question 38

Pretensioning. when the steel strands are released the concrete member usually

Answer 38

takes on a slight upward deflection

Question 39

The reinforcing steel used concrete is essential to the strength of

Answer 39

a reinforced concrete member

Question 40

As a general rule reinforcing steel should not be cut in the course of firefighting operations unless

Answer 40

It is necessary to rescue trapped victims

Question 41

The forces that are produced in the prestressing process remain locked in the steel for

Answer 41

The steel for the life of the assembly

Question 42

Cutting through reinforcing steel with a saw or torch is particularly dangerous in

Answer 42

Posttensioned concrete because the steel is not bonded to the concrete