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BC 3rd > Ch. 10 Concrete Construction > Flashcards

Ch. 10 Concrete Construction Flashcards

1
Q

Advantages of concrete (4)

A

Produced from RAW materials (locally available/low in cost).
Does NOT BURN.
Resists INSECTS and effects with contact of SOIL
Create a variety of architectural SHAPES

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2
Q

Concrete produced from: (3)

A

Portland cement
Aggregates
Water
mortar=Portland cement, sand, lime, water

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3
Q

Aggregates make up a ______ percentage of TOTAL VOLUME of concrete

A

Large

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4
Q

Curing concrete requires: (2)

A

Correct hydration

Temperature control

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5
Q

Hardening of concrete is chemical process called

A

Hydration

heat of hydration-cement forms gel, gel gives off heat

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6
Q

Keeping concrete moist (4)

A

Sprinkling.
Ponding.
Covering with plastic film.
Sealing compounds (to slow evaporation)

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7
Q

Temperature for concrete curing

A

Ideally between 50-70F

  • at or above 100F not reach proper strength
  • near freezing, harden slower
  • massive structures, heat of hydration adversely affects strength*
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8
Q

During curing, concrete will _________. Concrete hardens ______. Normal design strength reached ______.

A

SHRINK slightly
InDEFINITELY at a gradual rate
AFTER 28 days

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9
Q

Concrete types (7)

A 
Ordinary stone
Structural lightweight 
Insulating lightweight 
Gypsum
High early-strength
Expansive
Water-permeable
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9
Q

Coloring can be added for _______________. Such as coloring concrete when _____________.

A

Aesthetic or safety reasons.

It is placed over buried electric cables

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10
Q

Concrete.
Density reduced _____.
Flows more freely _____

A

Admixture, such as shale or clinker.

Superplasticizer

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11
Q

Ultimate compressive strength of concrete

A

2,500-6,000 psi

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12
Q

Techniques to reinforce concrete: (2)

A 
Ordinary reinforcing
Prestressing reinforcing (pretensioning and posttensioning)
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13
Q 
Ordinary reinforcing (3)
(Steps)
A

Concrete COMPACTED around rebar
Mechanical VIBRATOR
Concrete hardens and ADHERES to deformities on surface of bars

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14
Q

Ordinary reinforcing.

Job of design engineer to specify: (3)

A

Number of reinforcing bars
Their size (diameter)
Depth of concrete cover

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15
Q

Diameters of standard-size reinforcing bars

A

.375 - 2.257 inches

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16
Q

Fundamental tensile and compressive forces are ________ throughout a beam.

A

NOT UNIFORM

Diagonal tension forces also must be resisted

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17
Q

Vertical reinforcing bars are known as ____ and resist the ____ tension.

A

Stirrups

Diagonal

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18
Q

Concrete BEAMS are frequently cast in the shape of a _____.

A

Tee

reinforcing steel placed in the bottom of the tee to resist TENSILE force

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19
Q

Although the primary function of placing reinforcing steel in concrete is to resist _______ forces, the steel can also be used to support some of the _______ forces.

A

Tensile.

Compressive

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20
Q

Steel bars support some of the compressive load and also resist ____________ in the column from sources such as ____ and _____. Compressive forces in column great enough to cause steel bars to buckle. To avoid, lateral reinforcing provided ________.

A

Bending forces.
Wind.
Settling.

Around vertical bars

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20
Q

Ordinary reinforcing has inherent limitations.

Concrete beam/floor slab supports a load, concrete in the beam in tension is ___________.

A

Doing NO work

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21
Q

In ________, a _____________ is induced in the concrete before the load is applied

A

PreSTRESSing

Compressive force

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22
Q

Preloading of the steel creates ________ stresses in the concrete that counteract the ______ stresses that result when the loads are applied.

A

Compressive

Tensile

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23
Q

Prestressing process requires _____ loads to be applied to the concrete along the _______ of the beam. These loads can result in the _____ of the concrete over time.

A

Large
Axis
Shortening

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24
Q

The forces that are initially applied in the prestressing process are __________ than the forces theoretically needed to support the concrete and the applied loads.

A

Slightly higher

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25
Q

In pretensioned concrete, ______ are stretched between anchors producing a ___________ in the steel. Concrete is then placed around the steel.

A

Steel strands

Tensile force

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26
Q

Pretensioned: After the concrete has hardened sufficiently, the force applied to the steel strands ________. As the force on the strands is released, the strands exert a ___________ on the concrete.

A

Is released

Compressive force

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27
Q

In pretensioned concrete, when the steel strands are released, the member usually takes on a _____________ deflection.

A

Slightly upward

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28
Q

In posttensioned, the reinforcing steel is not tensioned until ___________.

A

AFTER the concrete has hardened. (Post)

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29
Q

As a general rule, reinforcing steel ____________ in the course of firefighting operations unless it is necessary to ______.

A

Should not be cut

Rescue trapped victims

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30
Q

Cutting through reinforcing steel with saw or torch is ____________ because the steel is ____________. If they are cut, they are likely to ___________, injuring emergency responders. __________ may also lead to the failure of the concrete structural element, resulting in a collapse or partial collapse.

A

Particularly dangerous in POSTTENSIONED concrete
Not bonded to the concrete
Spring out of the concrete
RELEASING the posttensioned element

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31
Q

_____ is placed into forms at the building site as a wet mass and hardens in the forms OR
_____ is concrete that is poured into forms as liquid and assumes the shape of the form in the position and location it will be used.

A

Cast-in-place

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32
Q

Cast in place permits the designer to cast the concrete in a _____________.

A

Wide variety of shapes

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33
Q

Wet concrete is transported from the truck to formwork either by _____ or ______.

A

Hoisting it in large buckets

Pumping

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34
Q

Great care must be exercised in the ____, ____, and ____ of concrete to ensure good quality.

A

Mixing
Placing
Curing

35
Q

The ______ of concrete is of significance to firefighters. Concrete that is of poor structural quality will behave poorly under fire conditions by ______ and even _________.

A

Quality

Spalling
Breaking apart

36
Q

The single MOST IMPORTANT factor in determining the ultimate STRENGTH of concrete is the __________.

A

Water-to-cement ratio

37
Q

An amount of water GREATER than required for curing is added to the concrete mix to _________________ as its placed in the forms.

A

Increase its workability

38
Q

The presence of ________ in the concrete also produces _______ due to ____________.

A

Excess moisture
Spalling in the concrete
Freezing conditions OR the heat of fire

39
Q

When concrete __________________, it’s quality checked by ________ known as a _______.

A

Arrives at the job site
Administering a test
Slump test

40
Q

Slump test is used to ___________ by measuring the amount that a ____________ of the concrete settles or _______ after it is removed from a __________ test mold.

A

Check the moisture content of concrete
Small, cone-shaped sample
Slumps
Standard-sized

41
Q

Concrete with ______ slump will fail the test and may be rejected by the ____________.

A

Excessive

Structural engineer

42
Q

Another method of testing concrete is to _______________ and subject them to ___________.

A

Make small test cylinders of a concrete batch

Compression testing

43
Q

Compression test: this method is ______ but has the disadvantage of requiring that the _______________ before the results are known. This test would be __________ if the concrete were ultimately found to be _________.

A

Accurate
Concrete be permitted to harden
Very costly
Unsatisfactory

44
Q

Large cast-in-place structures cannot be cast in _________. _________ unavoidably occur between _____________.

A

One operation

Construction joints
Successive pours

45
Q

Cast-in-place.

To provide for transfer of __________ from one placement to the next, the reinforcement steel will _________.

A

Loads and forces

Overlap the joints

46
Q

The following are common cast in place structural systems: (3)

A

Flat slab
Slab and beam
Waffle construction

47
Q

_______ is a simple system that consists of concrete slab supported by concrete COLUMNS

A

Flat-slab concrete frames

slab with columns

48
Q

Flat-slab concrete frames
The slab of concrete varies in thickness from _________. _______ stresses develop in the concrete where the slab intersects the supporting column.

A

6 to 12 in.

Shear

49
Q

Flat-slab
In a building that will have heavy live loads, the area around the columns is reinforced with additional concrete in the form of ____ or _______. If the building will support light loads, additional reinforcing _________ and this is called ________.

A

Drop panels or mushroom capitals

Is not necessary
Flat plate

50
Q

_______ is a simple system that consists of concrete slab supported by concrete BEAMS

A

Slab and beam framing

aka concrete joist construction

51
Q

Slab and beam
This framing system is ________ and is best suited for buildings with ____ floor loads. Slabs in this type of construction can sometimes be as thin as ______.

A

Extremely light weight
Light
2 inches

52
Q

Slab and beam
Due to the thin slab, the concrete beams must be ______ in order to provide adequate support. The spacing often gives an appearance similar to ________ and is sometimes referred to as ___________.

A

Closely spaced
Wood joists
Concrete joist construction

53
Q

Slab and beam
Concrete beams run MAINLY in one direction, _____________ slab.
Concrete beams running in two directions, ______ construction.
Two-way framing where spans are ____ and _____ loadings are high.

A

One-way reinforced
Two-way slab
Short
Floor

54
Q

Bldgs using ________ are often highly susceptible to fire damage due to their thin nature. Fire proofing is _________.

A

Slab and beam

Often necessary

55
Q

Waffle construction
Pattern result from placement of _______ over which ________ is placed.
This design provides a ______ slab while reducing the weight of _______ in the ____ half of the slab.

A

Square forms
Wet concrete

Thicker
Unnecessary concrete
Bottom

56
Q

Waffle
Reinforcing steel placed in the bottom of the formwork provides reinforcement in ___________. Slabs of this type, therefore, are also known as __________.

A

Two directions

Two-way slabs

57
Q

A poured concrete slab can be supported by _________ instead of _________.

A

Structural steel beams
Concrete beams
Type 1, must be provided fireproofing

58
Q

______ concrete is placed in forms and cured at a location other than the construction test.
Poured and set according to specification in a controlled environment

A

Precast

59
Q

The precast structural shapes, including ____, ____, and _____ are transported to the job site and hoisted into position.

A

Slabs
Wall panels
Columns

60
Q

Several advantages to using precast concrete: (1 of 3)

A

Higher degree of quality control

  • sheltered environment/not exposed to weather
  • high degree of quality control
  • mixing and pouring more mechanized
61
Q

Several advantages of using precast (2 of 3)

A

Work can proceed more quickly

  • no need for formwork at site
  • no need to wait for concrete to harden
  • no need to construct/remove forms, add’l costs
62
Q

Several advantages of using precast (3 of 3)

A

Precast concrete sandwich panels can be produced using polystyrene core (insulating properties)

63
Q

Major disadvantage to using precast is:

A

Need to transport the finished components to the job site.-Transportation increases cost and limits the size of the shapes.

64
Q

Precast concrete structures have more in common with _____ than with cast-in-place concrete buildings.

A

Steel-framed buildings

65
Q

Precast concrete SLABS for floor systems can be cast in standard shapes that include: (4)

A

Solid slabs (short spans up to approx. 30 ft)
Hollow-core slabs
Single tee slabs (tee slabs - spans up to 120 ft)
Double tee slabs

66
Q

A common form of construction with PRECAST is known as _________. Reinforced wall panels cast in horizontal casting beds. After _________, the wall panels are tilted up into the vertical position by a crane. Temporary bracing until roofs or permanent horizontal.

A

Tilt-up (precast) OR
Tilt-slab

Concrete has cured

67
Q

Tilt-up walls can be ______ stories in height. Tilt-up walls can support several types of roof including: (4)

A

Several

Timber beams
Precast slabs
Steel beams
Steel trusses

68
Q

Precast structural elements are usually _______ than corresponding cast-in-place components. However, the use of precast concrete results in a ___________________ that is inherent with cast-in-place concrete frames.

A

Lighter

Loss of continuity

69
Q

In a precast concrete structure, the connections between the individual components are _________ of structural engineering.

A

Critical aspect

70
Q

A variety of techniques, such as _____, _____ and ______ can be used to connect precast structural elements.

A

Bolting
Welding
POSTtensioning

71
Q

Precast.

Simple designs of this type are not inherently rigid and the slabs need to be ________ to resist _______.

A

Laterally tied together

Horizontal forces

72
Q

Short steel beam cast into the precast column.
Precast beams are secured to the column through the use of _________ cast into the columns or though the use of ___________.

A

Steel angles

Posttensioned steel cables

73
Q

When precast beams are to be supported by columns, the beams may be supported by _______ cast into the column. _______ is a ledge that projects from the column and supports the beam.

A

Corbel (also known as a bracket)

74
Q

Very common precast for parking garages.

The _____ and ______ make precast structural systems a practical choice.

A

Floor loads

Span lengths

75
Q

Concrete

Buildings supported by a ________ are usually enclosed by a non-bearing curtain wall.

A

Concrete frame

76
Q

Curtain wall/concrete frame.

The choice of material is determined by _______, ________ and ______.

A

Architectural style
Thermal insulation properties
Cost

77
Q

________ concrete systems may be somewhat more vulnerable to failure than _______________ concrete.

A

Prestressed

Ordinary reinforced

78
Q

Reinforcing cables and rods used in prestressed systems are made of high-strength steels that have lower yield points, can yield at a temp of _______.

A

Around 752F

79
Q

Concrete structural systems.

Fire resistance of concrete assembly is affected by such variables as: (5)

A 
Density
Thickness
Quality
Load supported by concrete
Depth of concrete cover over reinforcing bars
**concrete = 1 to 4 hrs**
80
Q

Structural lightweight concrete has a _____ density than ordinary concrete and has a _________ thermal conductivity. Therefore, it acts as a ______________ against a heat of fire than ordinary concrete. However, it is not used for _____________.

A

Lower.
Lower

Better insulator.
Load-bearing members

81
Q

__________ concrete buildings have an advantage over _________ buildings because of the continuity of the assembly provides an inherent restraint to movement of the ___________, such as _________.

A

Cast-in-place
Precast
Intersecting members
Columns and beams

81
Q

Spalling of concrete will result in ________ and __________.

A

Failure of the reinforcing bars

Failure of the structural assembly

82
Q

Spalling.

The expansion of water creates ________ forces within the concrete.

A

Tensile

84
Q

EXTENT to which concrete undergoes spalling depends on ________________. (2)

A

Amount of excess MOISTURE.
Length of TIME since concrete was placed
Extent=EMT

85
Q

SEVERITY of spalling also depends on: (2)

A

DURATION and SEVERITY structures exposure to the fire

severity IS severity!

86
Q

Concrete has good insulating properties and tends to retain the heat of an exposing fire and release it slowly, similar to masonry oven. This general effect is referred to as _______.

A

Heat sink effect

BC 3rd (9 decks)

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