Concrete(BB-CH6)

Question 1

(True or False) Concrete has high ability to resist stretching, bending, and twisting.

Answer 1

false

Question 2

What principle factor controls the strength of concrete?

Answer 2

water cement ratio

Question 3

(True or False) The major factor controlling the durability of concrete is its strength.

Answer 3

true

Question 4

If more water is added to a concrete mix than is needed to hydrate the cement, the
concrete becomes less_______.

Answer 4

watertight

Question 5

The production of good concrete is impossible unless good quality materials are used in the
mix, and this mix is properly_______.

Answer 5

worked and cured

Question 6

Portland cement is manufactured from finely ground limestone mixed with which of the
following materials?

Answer 6

any of the above

Question 7

For highway construction, Type III Portland cement is sometimes preferred to Type I
because Type III has which of the following characteristics?

Answer 7

shorter curing time

Question 8

What type of cement was developed for use in areas subject to severe frost and ice
conditions?

Answer 8

air entrained

Question 9

(True or False) Aggregate is the material combined with cement and water to make
concrete.

Answer 9

true

Question 10

Concrete is denser and stronger when which of the following conditions is met?

Answer 10

all voids are filled

Question 11

(True or False) When performing a sieve analysis of aggregate, you should determine the
percentage of material retained on the sieve.

Answer 11

true

Question 12

(True or False) To prevent aggregate from segregating during stockpiling, you should build
up piles in layers by dumping successive loads alongside each other.

Answer 12

true

Question 13

In concrete, how is laitance produced?

Answer 13

cement is hydrated with excess water

Question 14

The proportion of air-entraining agent added to a concrete mix should fall within what
range?

Answer 14

3-7%

Question 15

(True or False) The accepted use for retarders is to increase the rate of hydration.

Answer 15

false

Question 16

What is the main reason to store cement in a dry place?

Answer 16

To prevent it from setting too slowly and producing weak concrete

Question 17

When storing sacks of cement in a warehouse, what is the main reason to stack them close
together?

Answer 17

To restrict the circulation of air between them

Question 18

Before using warehouse-packed cement, what should you do to make it lump free?

Answer 18

roll the sacks around

Question 19

(True or False) In a field mix, the number of gallons of water per sack of cement must be
increased to allow for the saturated surface-dry condition of the sand.

Answer 19

false

Question 20

When available aggregate is 1 1/2 inches, what rule of thumb should you use to calculate
materials required for a proper concrete mix?

Answer 20

rule 42

Question 21

For each layer of concrete placed in a mold for a slump test, how many times should you
rod the mold?

Answer 21

25

Question 22

After completing a concrete slump test, you tap the side of the mix and the concrete
crumbles apart. What condition exists?

Answer 22

oversanded mix

Question 23

The rated capacity of a concrete mixing machine is determined by what factor?

Answer 23

The cubic feet of the mixed concrete

Question 24

(True or False) In cement batch-plant operations, the aggregate must pass through a
weigh box before being discharged into the mixer.

Answer 24

true

Question 25

In an 11-S concrete mixer, what maximum size aggregate can you use?

Answer 25

3 in

Question 26

In an 11-S concrete mixer, when should water be added to the mix?

Answer 26

After all the dry ingredients have been added

Question 27

You are to charge the skip of an 11-S concrete mixer. In what order should you add the dry ingredients?

Answer 27

aggregate, cemend, sand

Question 28

When using a large mixing machine, what minimum time should you mix 2 1/3 cubic yards of concrete?

Answer 28

2 min 15 sec

Question 29

It is now 12 noon and you just finished placing concrete. You should make sure the inside of the mixing drum is cleaned no later than?

Answer 29

1330

Question 30

When cleaning a mixing drum, you should place the coarse aggregate in the drum and turn for how long?

Answer 30

5 min

Question 31

When concrete must be discharged more than 4 feet above the level of placement, why should it be dumped into an elephant trunk?

Answer 31

to reduce segregation

Question 32

It is now 12 noon and you begin mixing concrete in a mixing drum. The concrete should be dumped no later than what time?

Answer 32

1330

Question 33

What type of concrete mixer can mix concrete en route to the jobsite?

Answer 33

transit mix truck

Question 34

In building construction, what is the most common type of forming material?

Answer 34

wood

Question 35

What type of joint should you use to make watertight concrete forms?

Answer 35

tongue and groove

Question 36

The hydrostatic head exerted on forms during concrete-placing operations normally continues for what maximum time?

Answer 36

1 1/2 hr

Question 37

(True or False) Footings for any foundation system should always be placed below the frost line.

Answer 37

true

Question 38

An exterior wall that serves as an enclosure and also transmits structural loads to the foundation is called

Answer 38

both a and b

Question 39

Which of the following phrases best defines the term "keyway" in a concrete footer?

Answer 39

The indentation in the center of the footer

Question 40

Horizontal form members that tie prefabricated panels together are called_______.

Answer 40

walers

Question 41

(True or False) Braces are not part of concrete form design and provide no additional strength.

Answer 41

true

Question 42

What type of form-tying device is used with cone nuts?

Answer 42

tie rod

Question 43

When constructing stair forms, you should extend the platform what approximate distance past the sides?

Answer 43

12 in

Question 44

Of the following, which is the best bond breaking agent to use on steel forms?

Answer 44

marine engine oil

Question 45

(True or False) A light film of rust or mill scale is acceptable on rebar.

Answer 45

true

Question 46

Which of the following rebar ties should you use when a finished mat is to be lifted by crane?

Answer 46

saddle tie with a twist

Question 47

When a column assembly of reinforcing bars is raised into place, the reinforcing steel is tied to the column form at intervals of

Answer 47

5 ft

Question 48

(True or False) In footing construction, stones may be used instead of steel supports under reinforcing bars.

Answer 48

true

Question 49

A joint that separates a floor slab from a column is called

Answer 49

isolation joint

Question 50

A joint that allows the transfer of part of the load from one structural element to another through the use of keys or dowels is called a

Answer 50

construction joint

Question 51

What type of blade is normally used to cut seasoned concrete?

Answer 51

diamond

Question 52

(True or False) High quality concrete requires both a well designed mix and good placing procedures.

Answer 52

true

Question 53

What is the maximum distance concrete should be dropped from a chute?

Answer 53

4 ft

Question 54

When placing concrete on a slope, you should start at what position?

Answer 54

bottom only

Question 55

What is the best tool for compacting concrete?

Answer 55

mechanical vibrator

Question 56

(True or False) It is permissible to use a mechanical vibrator to move concrete in forms.

Answer 56

false

Question 57

Which of the following procedures is used to bring a concrete surface to the required elevation?

Answer 57

screeding

Question 58

The speed at which a vibrating screed is pulled across concrete directly depends on which of the following factors?

Answer 58

the slump of the concrete

Question 59

(True or False) Troweling a vibrator screed finished floor slab is usually delayed because of the slow setup time needed for the concrete mix.

Answer 59

false

Question 60

Which of the following finishing tools gives concrete a smooth, dense, finished surface?

Answer 60

steel trowel

Question 61

Which of the following processes produces a nonskid or rough concrete surface?

Answer 61

brooming

Question 62

Concrete made with ordinary cement is generally cured for what minimum period?

Answer 62

3 days

Question 63

(True or False) When curing flat surfaces, ponding allows the concrete to maintain a uniform temperature.

Answer 63

true

Question 64

Which of the following materials is the best insulator?

Answer 64

straw

Question 65

When plastic is used in the concrete curing process, what is the minimum overlap for adjacent sheets?

Answer 65

12 in

Question 66

When patching concrete, you should apply mortar in layers NOT exceeding what maximum thickness?

Answer 66

1/2 in

Question 67

Of the following surfaces, which is best for precast concrete?

Answer 67

concrete

Question 68

At what point in concrete casting should the bond-breaking agent be applied to a casting surface?

Answer 68

after edge forms are placed

Question 69

What is the simplest method for pickup of small cast panels?

Answer 69

2 point

Question 70

What is the most common type of brace used in tilt-up concrete construction?

Answer 70

tubular

Question 71

(True or False) Because of their flexibility and tendency to stretch, cable braces are unsuitable for most projects.

Answer 71

true

Question 72

In cast concrete, sand streaking is caused by

Answer 72

escape of moisture from loose forms

Question 73

Compared to cast-in-place panels, precast panels have what main advantage(s)?

Answer 73

all of the above