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TONY: NC Contractor Exam > Concrete > Flashcards

Concrete Flashcards

1
Q

What is the maximum that sheathing should be cut back on tendons?

A

1 inch

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2
Q

What is the purpose for post-tensioning concrete?

A

To increase compressive strength in the bottom of a joist or girder to offset tensile stress

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3
Q

On concrete thickness up to about seven inches, which of the below are true about air content to slump?

A

Air content increases as slump increases

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4
Q

of the below would increase the abrasive strength of concrete?

A

1 – Low water-cement ratio 2 – Steel - troweled surface 3 – Harder aggregate 4 – All of these

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5
Q

What is the purpose of using vibrators when doing concrete work?

A

1 – Get rid of air voids 2 – Consolidates the concrete 3 – Moves fine aggregate to bottom 4 – Both 1 and 2

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6
Q

Usually air-entrained lightweight concrete has a slump of 2 to 4 inches, what would be the maximum slump you would seldom exceed?

A

5 Inches

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7
Q

– Tools used for finishing air-entrained concrete should be constructed from which of the below?

A

Aluminum or magnesium

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8
Q

Normal weight and lightweight concrete exposed to freezing and thawing or deicing chemicals shall be ________.

A

Air entrained

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9
Q

Samples for strength test for each class of concrete placed each day shall be taken not less than once a day or less than once for each ___________ .

A

150 cubic yards

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10
Q

What would you use to keep concrete forms from spreading apart?

A

Snap ties and brackets

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11
Q

Hotter than normal temperatures when pouring concrete has what consequences (or “What is true” about pouring concrete in hot weather?)

A

1 – Increased slump loss 2 – Increased tendency for cracking 3 – Long term strength loss4 – All of the above

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12
Q

temperatures have what effect (or it may have asked what is true) on fresh concrete.

A

Concrete that has been frozen will not be as impermeable as concrete that wasn’t frozen

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13
Q

Retempered concrete or concrete that has been remixed after initial set shall not be used unless approved by?

A

Registered design professional

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14
Q

what is the minimum cover on #5 rebar where permanently exposed to earth?

A

3 inches

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15
Q

Once water is added to a concrete mix at the mixing plant, what is the maximum time for delivery and discharge from truck?

A

1 ½ hours

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16
Q

The minimum strength of a concrete wall not exposed to the weather after 28 days is:

A

2500 psi

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17
Q

What is true about moisture in concrete?

A

1 – It is important to prevent moisture from leaving the concrete 2 – It is important to not prevent moisture from leaving the concrete3 – Excessive moisture loss will result in concrete cracking 4 – Both 1 and 3

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18
Q

Steps in footings should be used when slope exceeds:

A

10%

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19
Q

pumping concrete into tightly reinforced forms which of the below should be used?

A

Superplasticizers

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20
Q

What would you use to laterally support concrete forms?

A

Whalers and braces (tied and braced)

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21
Q

On concrete beams, what is the recommended distance between tendons/cables?

A

1 ½ inches

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22
Q

Concrete that is exposed to salt water, what is the correct mixture added to protect rebar?

A

Corrosion resistant mixture

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23
Q

How much concrete coverage is required when you have a # 10 rebar in a beam?

A

¾ inch

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24
Q

Low slump means that the concrete is;

A

Stiff

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25
Q

What is the minimum thickness required for a concrete slab placed against and permanently exposed to the earth?

A

3 ½ inches

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26
Q

Which of the following is not acceptable when grouting stressing pockets?

A

Having chlorides as an additive

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27
Q

When back stressing a barrier cable, the end anchor should be installed to a force of ___%

A

80%

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28
Q

The maximum number of or .60 of an inch tendons / cables in a group is _____.

A

4

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29
Q

For an encapsulated post-tensioned system, the watertight cap should be installed less than____.

A

24 hours after stressing

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30
Q

Which of the following is not a method to control plastic shrinkage?

A

Use of a richer mix design

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31
Q

High early strength concrete is made using Type _____ cement.

A

III

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32
Q

of the following are methods of curing concrete except _____.

A

1 – Keeping the surface moist 2 – Heated forms 3 – Covering with plastic sheets 4 - Using plastic forms

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33
Q

Which of the following concrete joints allows for both vertical and horizontal movement?

A

Isolation

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34
Q

For the strength of concrete to continue to increase with time, the relative humidity within the concrete should remain above____ percent.

A

80%

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35
Q

Which of the following factors does not influence workability of concrete?

A

Calcium chloride

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36
Q

Durability of concrete can be related directly to:

A

Compressive strength

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37
Q

What is the most effective method for controlling shrinkage cracking in concrete?

A

Providing joints (contraction joints)

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38
Q

The resistance of hardened concrete to freezing and thawing is significantly improved by adding:

A

Air – entrainment

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39
Q

What is the effect of vibratory action on a concrete mixture?

A

1 – It permits the use of a stiffer mixture 2 – It causes the mix to be more liquid 3 – Removes trapped air 4 – All of the above

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40
Q

What is the effective period of time for increased workability that can be expected when placing concrete using super plasticizer?

A

30 to 60 minutes

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41
Q

What is most closely related to abrasive strength of concrete?

A

Compressive strength

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42
Q

How do higher temperatures at time of placement affect concrete?

A

Concrete has a lower slump

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43
Q

Besides the water to cement ratio, what else determines the final compressive strength of concrete?

A

Age

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44
Q

The most common plasticizer used in concrete is:

A

Lime

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45
Q

For the most part you do not need to add anything to the concrete mix other than the standard ingredients, but on occasion additives do help to make the job easier. Which of the below is not considered an additive?

A

1 – Air entraining powder 2 – Plasticizers 3 – Retarders 4 – Water

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46
Q

Concrete in which wires are tensioned on the jobsite after the concrete has been hardened by running the wires through ducts is called

A

Post-Tensioned concrete

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47
Q

What is the minimum 28 day compressive strength for lightweight aggregate concrete?

A

2500 psi

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48
Q

If you order and are pouring one cubic yard of concrete 4 inches thick, which of the following forms would it fill?

A

9 feet ½ inch x 9 feet ½ inch Design and Control of Concrete Mixtures Calculations Divide 27 cubic feet (one yard) by inches (.33) and then square root to get the square dimensions. You may have to take answers given (if not square) and multiply and then multiply by inches and divide by 27

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49
Q

The concrete arrives on a construction project stiffer that needed and the workers add water to the mix. How will this affect the mix?

A

1 – Does not affect the mix 2 – Makes the mix weaker 3 – Increases the water to cement ratio 4 – Both 2 and 3

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50
Q

A footing needs to have a load supported on it of 252 kips, with a soil bearing capacity of 6,000 pounds. How many square feet will this footing have to be?

A

42 square feet

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51
Q

When placing concrete, what is the maximum distance it is allowed to fall before a tremie chute is required?

A

4 feet

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52
Q

What is the purpose for vibrating concrete?

A

1 – To remove trapped air 2 – To consolidate the concrete 3 – To separate the ingredients 4 – Both 1 and 2

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53
Q

When truck concrete mixers are used, the time between batching and complete discharge after water has been added to the cement and aggregates is ____ hours or before the drum has revolved ___times.

A

1 ½ hours and 300 revolutions

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54
Q

When mixing concrete, the reason for adding water to the cement is called:

A

Hydration

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55
Q

What temperature range would be considered a hot weather condition for concrete?

A

77 degrees to 90 degrees

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56
Q

What is the definition of creep in concrete?

A

The continuous deformation of the concrete due to continued sustained loads

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57
Q

If you have a pier or pier footing that is 7’0” x 7’0” by 1’6” deep using 4,000 psi concrete. The soil that this footing is sitting on has a bearing capacity of 2,000 pounds per square foot. What is the maximum load that soil can bear with this footing in kips?

A

98 kips

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58
Q

What is the definition of pre-cast concrete?

A

that is cast and poured off site and transported to its final position

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59
Q

What is the best temperature for curing concrete?

A

55 to 73 degrees (actually 50 to 70)

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60
Q

Which of the below would be the correct splice lap for splicing reinforcement rods (rebar) together in masonry?

A

40 times the bar diameter, minimum one foot of splice

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61
Q

What is the main reason for taking a slump test?

A

Check the workability and consistency of the concrete

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62
Q

When pouring concrete in hot weather, this is a condition that can occur:

A

1 – Shrinkage cracks 2 – Loss of strength 3 – Fast hydration (stiff very quickly) 4 – All of the above conditions

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63
Q

To resist the deterioration of concrete due to deicers, freezing and thawing, which of the following admixtures need to be added?

A

Air-entrainment

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64
Q

What is the purpose for using form ties when pouring concrete in forms?

A

To resist the lateral pressure of the concrete 4 – Neither of the above

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65
Q

When installing post tension cables, you are allowed to have 1 inch of the cable exposed in the concrete at the end tying into the form without plastic sheathing. What procedures are required if more than 1 inch is exposed?

A

Grease cable and tape

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66
Q

How can you stop reverse curvature of a post tension cable?

A

– Add additional cable supports

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67
Q

does post tension cables have to have before concrete can be poured on them?

A

Covered in grease and plastic covering in place

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68
Q

What is the definition of a post tension cable?

A

1 – Reinforcing steel is housed in a plastic coating or sheath that prevents the concrete from bonding with the cable so it can be stressed after the concrete has hardened

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69
Q

What type of concrete is used to allow stripping forms the quickest?

A

Type III

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70
Q

What is the purpose for vibrating concrete?

A

Separate the course aggregate

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71
Q

What admixture needs to be added to concrete in hot weather conditions?

A

Retardant

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72
Q

When installing post tension cables, there needs to be at least ____ inches of cable protruding out of the form

A

12

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73
Q

What is the minimum reinforcing bar lap or splice for a # 5 bar with 40D?

A

25 inches: A # 5 bar is 5/8 of an inch or .625 of an inch x 40 diameters splice is 25 inches.A # 4 bar is 1/2 of an inch or .50 of an inch x 40 bar diameters is 20 inches

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74
Q

What is the minimum percent of the 28 day compressive strength of concrete before post tension cables can be stressed?

A

75%

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75
Q

Definition of Type II concrete

A

– Moderate / Low sulfate resistance

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76
Q

Definition of Type III Concrete

A

High early strength – early set

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77
Q

Definition of Type IV concrete.

A

Low heat of hydration

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78
Q

which of the below is true about the volume of concrete once it sets up?

A

Stays about the same (changes slightly)

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79
Q

What is the concrete coverage for folded plate members on # 6 thru # 18 reinforced bar not exposed to earth?

A

¾ inch

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80
Q

How are post tension cable / tendons installed?

A

Wrapped in plastic with PT applied

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81
Q

What are the proportions of concrete made up of?

A

Sand, cement, water and course aggregate

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82
Q

What effect does low slump have on concrete?

A

More stiff, hard to work

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83
Q

What is the definition of air-entrained concrete?

A

1 – Concrete that will have resistance to freeze – thaw conditions when exposed to water and de-icing conditions

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84
Q

What is the definition of superplasticizers?

A

High range water reducers that are added to concrete with a low-to-normal slump and water ratio to make high slump concrete.

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85
Q

What is the definition of slump?

A

It is a test for the rigidity (consistency) of uncured concrete.

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86
Q

What is the minimum thickness at the edge for plain concrete footing?

A

8 inches

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87
Q

What is a characteristic of pouring concrete at low (cold) temperatures?

A

Concrete gains very little strength at low temperatures

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88
Q

What is a common admixture to add to concrete to help hydration and strength when pouring in cold weather?

A

Accelerating admixture

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89
Q

What is the average size of course aggregates (rock/gravel) in concrete?

A

3/4 inch

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90
Q

How many days does it take for concrete to reach its minimum design compressive strength?

A

28 days

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91
Q

When using air-entrainment in concrete as an admixture it will help with the freezing and thawing conditions over the life of the concrete, air-entrainment also will:

A

Improve the workability

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92
Q

What is the next process after completion of the screeding of a concrete slab?

A

Bull float finish

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93
Q

What type of concrete finish does a driveway require?

A

Broom finish

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94
Q

When is reinforcement not needed in concrete?

A

Driveways

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95
Q

How do concrete forms maintain their shape?

A

Braced and wall tied

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96
Q

Where are construction joints located in concrete beams and slabs?

A

Middle third

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97
Q

What is the best method to brace and align concrete forms in masonry work?

A

Turnbuckles and pins

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98
Q

Turnbuckles and pins

A

TRUE

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99
Q

Insulating concrete is a light weight concrete with the aggregate of:

A

Perlite

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100
Q

What is the definition of low permeability of concrete?

A

– Low permeability will produce acid and corrosion resistance of concrete

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101
Q

What is the definition of high permeability of concrete?

A

– High permeability of concrete will cause reinforcing to corrode.

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102
Q

What is the most preferred method to consolidate concrete?

A

Mechanical vibrators

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103
Q

What is placed directly under a concrete slab on grade?

A

1 – Vapor barrier 2 – Crushed rock 3 – Compacted sub grade 4 – All of the above

104
Q

What type of admixture is high early concrete?

A

Accelerating admixture

105
Q

What is the diameter of a # 5 reinforcing bar?

A

5/8 inch

106
Q

When pouring concrete with reinforcement that will be exposed to seawater, what type of admixture should be used?

A

Corrosion inhibitors

107
Q

For lightweight concrete with an overdry density of 50 pcf (pounds per cubic feet) which of below is correct?

A

Maximum slump of 5 inches

108
Q

– Type II concrete is used for what kind of construction?

A

Moderate sulfate resistance

109
Q

Which of the following may be used to hold foundation wall forms together?

A

Snap ties and metal brackets

110
Q

When performing the final operation where two extensions of the stressing jack are used, what is the percent of the final stroke of the jack?

A

60%

111
Q

which of the below statements is true about moisture when curing concrete?

A

It is important to prevent the loss of moisture from concrete during curing

112
Q

All of the following procedures apply during the preparation for concrete placement except:

A

Concrete should be retempered or remixed as needed

113
Q

What should be applied to hardened concrete to protect from deicing chemicals?

A

Air - entrainment

114
Q

What additive is used for concrete at high temperature or too hot?

A

Retardant

115
Q

which concrete joint allows both horizontal and vertical movement of concrete?

A

Isolation joint

116
Q

What is a common characteristic of low slump concrete?

A

Stiff

117
Q

Concrete that is low in heat and hydration is:

A

Type IV

118
Q

What is the last step before pouring concrete on post tension cables?

A

Install support bars

119
Q

What is true about how to finish light weight concrete?

A

Need to start finishing earlier than normal concrete

120
Q

What is the effect of algae in mixing water used for concrete?

A

Reduced strength

121
Q

What is the effect of high heat in concrete?

A

Reduced slump

122
Q

The abrasion resistance of concrete is dependent upon __________________.

A

Adequate curing

123
Q

The minimum overdry density for lightweight insulating concrete is _______pcf.

A

15

124
Q

Concrete cover is the minimum distance from the _______________.

A

Outside of the reinforcing bar to face of concrete

125
Q

What is the finish calculation for figuring the cubic yards of concrete if the beginning calculation is Length x?

A

Width x Depth (in feet) divided by 27

126
Q

What type of concrete has a low heat of hydration?

A

Type IV

127
Q

What type of concrete has a moderate sulfate resistance?

A

Type II

128
Q

What classification of reinforcing rod supports is used in situations where there will be maximum exposure but no grinding or sandblasting is required?

A

Class 1A

129
Q

The maximum spacing for rebar in a 6 inch thick wall should not exceed _______inches on center.

A

18 inches

130
Q

When placing reinforcing steel in a steel mat, where may the wire ties be placed if the spacing is not specified?

A

At every fourth or fifth intersection

131
Q

Short bars tied at right angles to main reinforcing bars in a floor slab are called “___________ bars”.

A

Temperature

132
Q

Which of the following items is NOT required to be identified by the markings on reinforcing steel?

A

A set of numbers indicating the date of fabrication

133
Q

Which of the below would be the best order to install post tension cables?

A

Forms set, install sleeves and embeds, cables, cable supports and install plumbing and electrical sleeves

134
Q

Stirrups are used in a concrete beam to resist:

A

Shear

135
Q

many pieces of rebar does a beam bolster chair support?

A

2

136
Q

Unreinforced structural plain concrete is used in all of the following except:

A

Columns

137
Q

Why should you use a chute for placing concrete instead of dropping it in place?

A

Helps concrete to not separate (without segregation)

138
Q

Which admixture is added in concrete to accelerate the rate of hydration and increase strength development at an early age?

A

Accelerating admixture

139
Q

The minimum standard reinforcing bar size is a ______bar.

A

2 – # 3 3 – # 4 The above answer # 3 bar is correct for this question but there is an exam question where a # 4 bar is the correct answer for the same question. I think that on that exam question that a # 3 bar is not listed as a possible answer

140
Q

What is used in concrete walls to hold metal reinforcing in place?

A

Tie wire

141
Q

What is the minimum spacing between bundles of tendons?

A

1 ½ inches

142
Q

Which of the below would be an admixture in concrete?

A

Air - Entrainment

143
Q

What is the range of air entrainment of light weight moderate exposure structural concrete?

A

5 to 8 %

144
Q

What is the best slump used for light weight concrete?

A

What is the definition of Type V concrete?

145
Q

What is the definition of Type V concrete?

A

High sulfate resistance

146
Q

What is the slump used for lightweight concrete that can be placed under conditions that would normally require a slump of 3 to 5 inches for normal-weight concrete?

A

2 to 3 inches

147
Q

Which of the below is correct for the standard reinforcing bar sizes?

A

3 through # 11, # 14 and # 18

148
Q

How many years of experience are needed to be a lead man for post tension cables?

A

5 years

149
Q

Which of the below would more likely require using a vibrator to consolidate concrete?

A

Mixture with aggregate

150
Q

What is the minimum support bar needed for cables in a post tension beam?

A

4

151
Q

What type of support would be used to hold a rebar mat 3 feet off the ground?

A

Standee

152
Q

Where are the temperature bars placed in a slab?

A

Right angles

153
Q

What is the purpose for putting composite sheathing over a post tension tendon?

A

Cable can move more freely in concrete

154
Q

What is the best type of joint to control cracking in a driveway?

A

Contraction

155
Q

What is the most widely used supplementary cementitious material in concrete?

A

Fly ash

156
Q

How many different sizes are there in reinforcing bars?

A

11

157
Q

What is the best type of concrete mix to use in a drain structure that requires moderate sulfate concrete?

A

II

158
Q

Which group of concrete uses expanded aggregates such as perlite?

A

I

159
Q

What is the best method for curing concrete?

A

Moist condition for 7 days at 50 degrees

160
Q

What is the proper method for vibrating concrete?

A

Insert vibrator quickly and remove when large air bubbles stop surfacing

161
Q

What is the most effective way to prevent water evaporation when curing concrete?

A

Fogging

162
Q

What is the relationship between concrete strength and hard aggregate?

A

Hard aggregate is more wear resistant

163
Q

What admixture in needed when placing concrete in areas of closely spaced and congested reinforcing steel to improve concrete flow without weakening the concrete mix?

A

Superplasticizer

164
Q

As a concrete beam is loaded and has the tendency to bend down, where in the beam would the reinforcing be placed to resist this tension?

A

Bottom

165
Q

Where are temperature bars placed in a joist?

A

On top of all other bars with support bars underneath them parallel to joist bars

166
Q

How much pcf of perlite is used in Group I lightweight concrete?

A

15 and 50 pcf

167
Q

Which of the below would prevent surface scaling of concrete?

A

Air entrainment

168
Q

What is the minimum depth of construction joints?

A

25% of slab (1/4 of slab)

169
Q

The maximum number of or .50 of an inch tendons / cables in a group is _____.

A

5

170
Q

A rebar splice is 25 inches using a 40D splice, what is the size of the rebar?

A

5Placing Reinforcing Bars Page 10-12Formula = 25 divided 40 = .625 x 8 = 5

171
Q

What of the below is not a characteristics of a slab on grade?

A

Grass and sod underneath

172
Q

What can be added to Group I light weight concrete that has 15 pcf of perlite?

A

Additional perlite

173
Q

Which of the following is not considered an aggregate in concrete and should be avoided?

A

Chert

174
Q

What is used to hold reinforcement together in a concrete wall?

A

Wrap and snap

175
Q

What type of tie wire is used to hold reinforcement together in a concrete wall?

A

Black soft-annealed

176
Q

What is the required temperature range for test cylinders to be stored in the field?

A

60 to 80 degrees F

177
Q

What is the minimum to maximum water to cement ratio for a concrete mix?

A

.40 to .50

178
Q

What are concrete cylinders tests used for?

A

To estimate concrete strength at a given time

179
Q

When you need concrete to set quickly, what type of concrete should be used to produce high early strength?

A

Type III

180
Q

What chemical reaction takes place when Portland cement is hardening?

A

Hydration

181
Q

What is the difference between fine and coarse aggregate?

A

The coarse stone will not pass through a 1/4” sieve

182
Q

What should be added to concrete in cold weather?

A

Calcium chloride

183
Q

Which of the following is not a reason to use an admixture?

A

To increase permeability

184
Q

What is the most noticeable characteristic of air-entrained concrete?

A

Increased workability

185
Q

What is the effect of adding too much water to a concrete mix?

A

Higher slump and lower strength

186
Q

Can fly ash be introduced into a concrete mix specifying a minimum cement content?

A

Yes, if called for by the specifier

187
Q

The maximum delivery time for ready mix concrete is:

A

90 minutes or 300 revolutions of the mixer drum

188
Q

Mat, raft, or floating foundations are specified when:

A

The allowable bearing capacity of the soil is very low to great depths

189
Q

What type of forms are used to place concrete by extrusion?

A

Slip-forms

190
Q

What is the minimal quality plywood that can be used when building concrete forms?

A

BB

191
Q

What is the best type of nail to use for nailing bracing and forms when the nails must be removed when the pour is completed?

A

Double headed or duplex nails

192
Q

Which of the following is the most economical wood to use for formwork?

A

Kiln-dried pine

193
Q

The usual safety factor for new form ties is:

A

2:01

194
Q

The purpose for form liners is to provide:

A

Special textures

195
Q

How much does concrete weigh per cubic foot?

A

150 lbs

196
Q

What is the best way to reduce lateral pressure on concrete forms when placing concrete?

A

Slower placement

197
Q

When an engineer’s specifications for removal of concrete forms is not available, the ACI has recommendations for the length of time concrete should remain in the forms when the aire temperature is above:

A

50 degrees

198
Q

What is the main reason for steel reinforcement in a concrete member?

A

To resist tensile forces

199
Q

Placing drawings show details for fabrication and:

A

Placing of reinforcing steel

200
Q

What are the characteristics of a #5 bar?

A

625” diameter, .31% area and 1.043 lbx. per LF

201
Q

What do the markings on rebar represent?

A

Producers mill, bar size, steel type and grade

202
Q

Lowering the top bars or raising the bottom bars by 1/2” more than specified in a 6” concrete slab could reduce it’s load carrying capacity by:

A

Approximately 20%

203
Q

What is the maximum variation of stirrup location in a floor slab?

A

+ or - 1”

204
Q

Which of the following is not a type of rebar splice?

A

Bundled

205
Q

What is the minimum length of lap in a lapped splice for reinforcing bars?

A

12”

206
Q

The most effective waterstops are made of

A

PVC

207
Q

To what depth should a contraction joint be cut into a concrete slab?

A

One-fourth the slab thickness

208
Q

How soon after pouring a slab should it be sawcut?

A

Within 4 to 12 hours

209
Q

What type of joint is used when concrete placement is interupted?

A

Construction joint

210
Q

What is the sole purpose for installing welded wire mesh in a concrete slab?

A

To prevent cracks

211
Q

What is the proper location of welded wire mesh in a concrete slab?

A

2” below the slab surface, in the upper third of the slab

212
Q

Most specifications allow only one addition of water as long as you do not exceed what?

A

The water to cement ratio

213
Q

What is the best shape of aggregate to use when pumping concrete?

A

Rounded

214
Q

When using a 5” diameter pump line, what is the ideal mix to pump?

A

4” slump with air entrainment containing some fly ash

215
Q

A concrete containing a lightweight aggragate should be presoaked to 70 to 80% total absorption. If not, it will:

A

Make pumping difficult

216
Q

When using a vibrator on concrete, it should not be kept in one location more than:

A

10 to 15 seconds

217
Q

What type of concrete finish creates a skid-resistant surface?

A

Broom finish

218
Q

Air-entrained concrete is most vulnerable to what tupe of problem?

A

Blistering

219
Q

What is the slump test used to measure in concrete?

A

Consistency

220
Q

Concrete that is specified to be exposed to freezing and thawing conditions should have what added to the mix?

A

Air entrainment

221
Q

What percent of the 28 day strength of concrete should be obtained in the first 7 days?

A

65 to 70 percent

222
Q

What is the most common type of Portland cement used in the construction field?

A

Type I

223
Q

The quality of the cement mix depends primarily on the:

A

Water-cement ratio

224
Q

What type of sand is not a suitable substitute for aggregate?

A

Fine sand

225
Q

What additive is used for concrete at high temperature?

A

Retardant

226
Q

What is the range of moderate slumps for most concrete?

A

3 to 4 inches

227
Q

Air entrainment should always be specified for concrete exposed to what?

A

Freezing and thawing

228
Q

What is the minimum temperature concrete should be poured on thin slabs?

A

60 degrees

229
Q

What is the maximum temperature that concrete should be when delivered to the jobsite?

A

90 degrees

230
Q

What report is required before driving test piles?

A

Geotechnical data

231
Q

What type of footing is used for columns on the exterior of the building when projection outside of the building is restricted?

A

Combined footing

232
Q

What is the most common type of spread footing mainly used to support a column?

A

Isolated

233
Q

Who is responsible for checking concrete loads on formwork in large structures and multistory buildings?

A

Structural engineer

234
Q

What type of concrete form will create a void inside of the floor or beams?

A

Internal

235
Q

Which type of form should be used when forming waffle slabs in a multi-story building?

A

Pan Forms

236
Q

What fabricated metal or plastic units hold forms secure against the lateral pressure of freshly placed concrete?

A

Form ties

237
Q

The working load of new ties used in formwork should have a safety factor of:

A

2:01

238
Q

Breaking concrete cylinders is the most common method for measuring concrete strength, what would be an alternative method for strength measuring?

A

Penetration

239
Q

What is the correct procedure for installing reshores under a newly stripped slab?

A

Snug, but not tight

240
Q

Concrete forms for slab-on-grade can be boards or metal frame and are set at:

A

Finish elevation

241
Q

What is the percent of the tensile strength of unreinforced concrete in relationship to the compressive strength of unreinforced concrete?

A

10 percent

242
Q

What is a primary use of welded wire reinforcement in flatwork?

A

Extending control joint spacing

243
Q

What are three types of concrete joint?

A

Construction, Isolation, and Contraction

244
Q

What type of joint permits the separate segments of the structural frame to expand and contract with temperature and moisture changes?

A

Contraction Joint

245
Q

Which type of concrete joint allows for horizontal and vertical movement?

A

Expansion

246
Q

What is the primary use of a mechanical vibrator on freshly poured concrete?

A

To consolidate the concrete

247
Q

What is used to cut off high points and fill in minor low points on a freshly poured concrete slab?

A

Checkrod (bullfloat)

248
Q

What type of bullfloat is best used to finish air-entrained concrete?

A

Aluminum or magnesium

249
Q

What problems are caused by pouring concrete in hot weather?

A

Lower strength, rapid drying time, shorter setting time

250
Q

Why is calcium chloride (added at a rate of one to two percent of the weight of the cement in the mix) used?

A

An Accelerator

251
Q

What is the most effective way to prevent water evaporation when curing concrete?

A

Fog spraying

252
Q

What will alleviate excessive bleeding in concrete?

A

Adding fly ash, adding fine sand, increasing cement

253
Q

What temperature should concrete cylinders be maintained at during the first 48 hours prior to testing concrete?

A

60-80 degrees

254
Q

Which types of concrete slabs are suitable for air-entrained concrete?

A

Driveway, Sidewalk, and Exterior slabs

255
Q

What is the most important factor in preventing surface scaling in concrete flatwork?

A

Air Entrainment

TONY: NC Contractor Exam (13 decks)

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