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cons mat unit 6 > unit 6 > Flashcards

unit 6 Flashcards

1
Q

______ makes the Concrete Workable and molded into the Desired Shape.

A

Water

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2
Q

The amount of water in concrete controls many fresh and hardened properties in concrete including
workability, compressive strengths, permeability, water tightness, durability and weathering, drying
shrinkage, and potential for cracking. (t or f)

A

t

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3
Q

The ratio of the amount of water, minus the amount of water absorbed by the aggregates, to the
amount of cementitious materials by weight in concrete is called the _____________________.

A

water-cementitious ratio

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4
Q

The w/cm ratio equation is?

A

w/cm= (weight of water – weight of water absorbed in the aggregates) divided by the weight
of cementitious materials.

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5
Q

Upon _________, the paste or glue consisting of the cementitious materials and water binds the
aggregates together.

A

hardening

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6
Q

Increasing the w/cm ratio also improves other hardened concrete properties by increasing the
density of the paste which lowers the permeability and increases water tightness, improves durability
and resistance to freeze-thaw cycles, winter scaling and chemical attack. (t or f)

A

f (decreasing)

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7
Q

Designers select maximum w/cm ratios and minimum strengths primarily based on exposure
conditions and durability concerns – not load-carrying capacity requirements. (t or f)

A

t

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8
Q

For different exposure
conditions, use the code required maximum w/cm ratios and minimum strengths to reduce the
permeability of the concrete. Doing so will decrease the concrete’s resistance to weathering. (t or f)

A

f (increase the concrete’s resistance to weathering.)

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9
Q

The most important factor affecting the amount of drying shrinkage and the subsequent potential
for cracking is the ___________________.

A

water content or the amount of water per cubic meter of concrete

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10
Q

concrete shrinkage increases with lower water contents (t or f)

A

f (higher)

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11
Q

About half of the water in
concrete is consumed in the chemical reaction of hydration and the other half provides the concrete’s
workability. (t or f)

A

t

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12
Q

Except for the water lost to bleeding and absorbed by the base material or forms, the
remaining water that is not consumed by the hydration process contributes to drying of shrinkage. (t or f)

A

t

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13
Q

The ease of mixing, placing, consolidating and finishing concrete is called __________.

A

workability

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14
Q

The ____________o f the mixture is the single most important factor that affects workability.

A

water
content

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15
Q

Adding more water to the concrete increases workability but more water also increases the potential
for segregation (settling of coarse aggregates particles), increased bleeding, drying shrinkage, and
cracking in addition to decreasing the strength and durability. (t or f)

A

t

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16
Q

If measured slumps are less than allowed by the specifications, slumps may be adjusted by a ____-
time addition of water.

A

one

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17
Q

in adding water onsite the water is should not exceed the maximum water content for the batch as established by the accepted
concrete mixture proportions (t or f)

A

t

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18
Q

in adding water onsite it is important that the concrete has been discharged from the mixer except for slump testing (t or f)

A

f (no concrete has been discharge)

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19
Q

in adding water onsite All water additions shall be completed within __ minutes from the start of the first water
addition.

A

15

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20
Q

in adding water onsite Water shall be injected into the mixer with such pressure and direction of flow to allow
for proper distribution within the mixer. (t or f)

A

t

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21
Q

in adding water onsite The drum shall be turned an additional __revolutions or more at mixing speed to ensure
a homogeneous mixture

A

30

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22
Q

Before adding water on the site, the allowable amount of water that can be added must be known. (t or f)

A

t

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23
Q

This amount should be printed on the delivery ticket or be determined after the pre-construction
meeting and be agreed upon by parties. (t or f)

A

f (during the pre-construction meeting)

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24
Q

______ is the key component in concrete.

A

Water

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25
Q

Water will be tested in accordance with and shall meet the suggested requirements of _________________

A

AASHTO
T26.

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26
Q

DPWH Standard Specifications for Highways, Bridges, and Airports Volume II, 2013
Edition, Sub-item 714.2 Requirements states that the ______________________________

A

mixing water shall be clear and
apparently clean.

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27
Q

t or fs
Water known to be of potable quality may be used without test.

A

t

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28
Q

what are the Two
criteria should be considered in evaluating the suitability of water for mixing concrete.

A

One is
whether the impurities will affect the concrete quality and the other is the degree of permissible
impurity. When the water quality is questionable, it should be analyzed chemically.

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29
Q

____________ is a material, other than water, aggregates, and hydraulic cement
(including blended cement) that is used as an ingredient of concrete and is added to the batch in
controlled amounts immediately before or during mixing to produce some desired modification to
the properties of the concrete.

A

admixtures

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30
Q

Air-entraining admixtures shall conform to the requirements of ___________

A

AASHTO M154

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31
Q

Chemical admixtures, if specified or permitted, shall conform to the requirements of____________

A

AASHTO M194.

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32
Q

Fly ash, if specified or permitted as a mineral admixture and as ___% partial replacement of Portland
cement.

A

20

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33
Q

Admixtures should be added only to the concrete mix to produce some desired modifications to the
properties of concrete when necessary, but not as a partial replacement of cement. T OR F

A

T

34
Q

admixtures that will decrease mixing water content by 5 to 12%, depending on the
admixture, dosage, and other materials and proportions.

A

type A- water-reducing admixture

35
Q

Admixtures that delay the time of setting of concrete

A

Type B – Retarding Admixtures

36
Q

An admixture that accelerates the time of setting and early strength development of concrete.

A

Type C – Accelerating Admixtures

37
Q

An admixture that decreases the quantity of mixing water required to produce concrete of a given
consistency and delays the time of setting of concrete.

A

Type D – Water-Reducing and Retarding Admixtures

38
Q

An admixture that decreases the quantity of mixing water required to produce concrete of a given
consistency and hastens the time of setting and early strength development of concrete.

A

Type E – Water-Reducing and Accelerating Admixtures

39
Q

An admixture that decreases the quantity of mixing water required to produce concrete of a given
consistency by 12 percent or greater

A

Type F – Water-reducing High Range, Admixture

40
Q

An admixture that decreases the quantity of mixing water required to produce concrete of a given
consistency of 12 percent or greater and delays the time of setting of concrete.

A

Type G – Water-Reducing, High Range, and Retarding Admixtures

41
Q

admixtures, used to improve and
extend workability time of freshly mixed concrete without negative effect on setting times)

A

Type S – Specific performance admixtures

42
Q

admixtures in which
pozzolanic activity can be expected

A

Fly ash, Silica fume, volcanic ash, Siliceous white clay, Diatomite

43
Q

admixtures which latent hydraulic can be expected.
It Improves durability of concrete

A

Ground granulated blast-furnace slag

44
Q

are admixtures that contribute to gaining high strength during
autoclave curing.

A

Siliceous fine powder

45
Q

decreases material segregation and/or bleeding of concrete
with high Flowability

A

Limestone powder admixtures

46
Q

If admixtures can be added to the solution, they are either weighed or measured by volume as
recommended by the manufacturer. (t or f)

A

f ( cannot be added)

47
Q

produce tiny air bubbles in the hardened concrete to provide space for water to expand
upon freezing.

A

Air entrainers

48
Q

mechanism taht contribute to the develepment of internal stresses in the concrete where Upon freezing, water expands in volume by 9%. If the percent saturation
exceeds 91.7%, the volume increases and generates stress in the concrete.

A

Critical saturation

49
Q

mechanism taht contribute to the develepment of internal stresses in the concrete where Freezing water draws unfrozen water to it. The unfrozen water moving
throughout the concrete pores generates stress, depending on length of flow path, rate of
freezing, permeability, and concentration of salt in pores.

A

Hydraulic pressure

50
Q

mechanism taht contribute to the develepment of internal stresses in the concrete where water moves from the gel to capillaries to satisfy thermodynamic equilibrium
and to equalize alkali concentrations. Voids permit water to flow from the interlayer hydration
space and capillaries into the air voids, where it has room to freeze without damaging the parts.

A

Osmotic pressure

51
Q

Air entrainers are usually powder and should meet the specifications of ASTM C260. (t or f)

A

f (liquid)

52
Q

______________ admixtures can be used indirectly to gain strength.

A

Water reducing admixtures

53
Q

Adding a water reducer without altering the other quantities in the mix increases the slump, which
is a measure of concrete consistency and an indicator of workability. (t or f)

A

t

54
Q

The strength of the mix can be increased by using the water reducer by lowering the quantity of
water and keeping the cement content constant. (t or f)

A

t

55
Q

The cost of the mix, which is primarily determined by the amount of cement, cannot be reduced. (t or f)

A

f (can be reduced)

56
Q

can either greatly increase the flow of the
fresh concrete or reduce the amount of water required for a given consistency.

A

Superplasticizers

57
Q

are used
for several reasons, such as the following:
1. Offsetting the effect of hot weather
2. Allowing for unusual placement or long-haul distances
3. Providing time for special finishes (e.g., exposed aggregates)

A

Retarders

58
Q

These admixtures have the ability to stop and reactivate the hydration process of concrete.

A

Hydration-Control Admixtures

59
Q

are used to develop the early strength of concrete at a faster rate than that developed
in normal concrete.

A

Accelerators

60
Q

used primarily to control
the cracking of a concrete structure and to maintain the structural integrity of the slab between
transverse joints.

A

steel

61
Q

Cracking of the slab will occur even though steel is present (t or f)

A

t

62
Q

The amount of phosphorous in steel is a critical quantity since, while a small amount of small
percentage (0.05 to 0.10%) the phosphorus causes “____________” a term applied to that
characteristic of steel, which makes it brittle when cold.

A

cold shortness

63
Q

Deformed billet-steel bars for concrete reinforcement shall conform to

A

AASHTO M31 (ASTM A 615)

64
Q

Deformed steel wire for concrete reinforcement shall conform to

A

AASHTO M225 (ASTM A 496)

65
Q

Welded steel wire fabric for concrete reinforcement shall conform to

A

AASHTO M55 (ASTM A 185)

66
Q

Cold-drawn steel wire for concrete reinforcement shall conform to

A

AASHTO M32 (ASTM A 82)

67
Q

Fabricated steel bar or rod mats for concrete reinforcement shall conform to

A

AASHTO M54 (ASTM A 184)

68
Q

Welded deformed steel wire fabric for concrete reinforcement shall conform to

A

AASHTO M221 (ASTM A497)

69
Q

Plastic coated dowel bars shall conform to

A

AASHTO M254 Type A

70
Q

Low alloy steel deformed bars for concrete reinforcement shall conform to

A

ASTM A 206

71
Q

_________ is the standard specification for Deformed and Plain Billet-Steel Bars for concrete
reinforcement in cut lengths and coils.

A

ASTM 615M

72
Q

steel bar without protrusions

A

Plain bar,

73
Q

longitudinal protrusions on a deformed bar

A

Rib,

74
Q

is the ability of a material to withstand a pulling (tensile force).

A

Tensile Strength

75
Q

the stress a material can withstand without permanent deformation

A

Yield strength

76
Q

– the maximum stress a material can withstand

A

Ultimate strength

77
Q

the stress coordinate on the stress-strain curve at the point of rupture

A

Breaking strength

78
Q

yield as the first stage of failure, some hardening in the second stage, and
breakage after a possible “neck” formation

A

Ductile failure

79
Q

sudden breaking in two or more pieces at a low stress state

A

Brittle failure

80
Q

is the point on a stress-strain curve that indicates the limit of elastic behavior and the
beginning plastic behavior.

A

yield point

81
Q

________ at fracture is conventionally expressed as a percentage of the original gauge length
of a standard test piece.

A

elongation

cons mat unit 6 (1 decks)

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