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(Construction Materials 101) > Lesson 5 - Concrete > Flashcards

Lesson 5 - Concrete Flashcards

1
Q

The strength of concrete is affected by the degree of its compaction. It is vital, therefore, that the consistency (ability to flow) of the mix be such that, the concrete can be transported, placed, and finished sufficiently, easily and without segregation

A

Fresh Concrete

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2
Q

Used to describe the ease with which concrete
mixes can be compacted (completely compacted using the lowest possible w/c)

A

WORKABILITY

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3
Q

Factors of Workability

A
  1. Water Content
  2. Maximum size of aggregate
  3. Grading of aggregates
  4. Shape and Texture of aggregates
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4
Q

Water Content

A

adding water
↑ workability,
↓ STRENGTH

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5
Q

Maximum size of aggregate

A

↓ surface area to be wetted, ↑ water in medium

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6
Q

Grading of aggregates

A

poor grading reduces consistency

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7
Q

Shape and Texture of aggregates

A

smooth Surface gives better workability

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8
Q

Measurements of Workability (Indirect)

A
  1. Slump Test
  2. Compacting Factor Test
  3. Flow Table Test
  4. VeBe Test
  5. Kelly Ball Test
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9
Q

Used in detecting variations in the uniformity of a mix of given nominal proportions

A

SLUMP TEST

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10
Q

SLUMP TEST - Stiff Mix

A

zero slump

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11
Q

SLUMP TEST - Rich Mix

A

slump varies but is satisfactory

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12
Q

SLUMP TEST - Lean Mix

A

shear or collapse slump

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13
Q

Measurement of the density ratio
(actual recorded density compared to the density of the same concrete that is fully compacted)

A

Compacting Factor Test

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14
Q

Measures the diameter of the spread after
vibration (Self Consolidation Concrete/Self
Compacting Concrete)

A

Flow Table Test

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15
Q

Measures the depth of penetration

A

Kelly Ball Test

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16
Q

Separation of the constituents of a heterogeneous mixture so that the distribution is no longer uniform.

A

Segregation

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17
Q

TWO FORMS OF CONCRETE SEGREGATION

A
  1. Coarse particles tend to separate out since they settle more than the fine particles
  2. Segregation on wet mixes (separation of water + cement) from the mix
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18
Q

Water from the mix tends to rise to the surface of freshly placed concrete. It can be expressed as the total settlement per unit height of concrete.

A

Bleeding (Water Gain)

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19
Q

a weak, friable layer on the surface of concrete
and sand cement screeds which appears after
curing.

A

Laitance

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20
Q

Consists essentially of the elimination of
entrapped air in concrete (ramming/vibration)

A

Compaction of Concrete

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21
Q

Types of Vibration

A
  1. Internal Vibration
  2. External Vibration
  3. Vibrating Tables
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22
Q

The creation of an environment for a period of
time (suitable temperature, prevention of loss of
moisture or providing moisture)

A

Curing of Concrete (Sample and Onsite)

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23
Q

Suitability of water for mixing and curing
processes should be considered, the quality of water is covered by saying water must be fit for drinking.

A

Quality of Mixing Water

24
Q

A type of concrete which is designed to be pump able with a relatively high slump (6-8”)

A

Pumped Concrete

25
Q

A special technique used to make concreting in
water (Tremie Method)

A

Underwater Concreting

26
Q

A product of the binding and hardening of the concrete mixture, which contains ingredients quantified in the appropriate proportions.

A

HARDENED CONCRETE

27
Q

ingredients quantified in the appropriate proportions for hardened concretes

A

binder (cement)
coarse aggregate (gravel)
fine aggregate (sand, fraction <2mm)
water and optional additives (> 5% by weight of binder)
admixtures (<5% by weight of the binder).

28
Q

a measure of the concrete’s ability to resist loads that tend to compress it. It is measured by crushing cylindrical concrete specimens in compression

A

Compressive Strength

29
Q

measure of the tensile strength of concrete. It is a measure of the ability of an unreinforced concrete beam or slab to resist failure in bending

A

Flexural Strength

30
Q

There is no field test for direct determination of
tension under axial loading. An indirect method
called the splitting tensile test, in which a standard test cylinder is loaded with compression on its side.

A

Tensile Strength

31
Q

____ is a loading in which a part of a member attempts to slide or ___ along another part. ____, which is a twisting, is also complex and difficult to evaluate. When concrete fails, a __________ causes the failure.

A

Shear, Torsion and Combined
Stresses

32
Q

is a loading in which a part of a member attempts to slide or move along another part.

A

Shear

33
Q

which is a twisting, is also complex and difficult to evaluate.

A

Torsion

34
Q

Besides its ability to sustain loads, concrete is also required to be resistant.

A

Durability

35
Q

It can be defined as its resistance to deterioration resulting from external and internal causes.

A

Durability

36
Q

It includes the effects of environmental and service conditions to which concrete is subjected such as weathering, chemical
actions and wear.

A

external causes

37
Q

are the effects of interaction between the constituent material such as alkali-aggregate reaction, volume changes, absorption and
permeability.

A

internal causes

38
Q

External Causes

A
  1. Leaching out of Cement
  2. Actions of sulphates, seawater and natural slightly
    acidic water.
  3. Occurrence of extreme temperatures, abrasion and
    electrostatic action.
39
Q

Internal Causes

A
  1. Alkali-aggregate reactions
  2. Volume change due to difference in thermal
    properties of the aggregate and cement paste.
  3. Permeability of concrete.
40
Q

is caused by the setting of solids and the loss of free water from the plastic concrete, by the chemical combination of cement with water, and by the drying of the concrete.

A

Shrinkage;
- plastic
- autogenous
- drying

41
Q

Types of Concrete Defects

A
  1. CRACKS
  2. CRAZING
  3. BLISTERING
  4. DELAMINATION
  5. DUSTING
  6. CURLING
  7. EFFLORESCENCE
  8. SCALING AND SPALLING
42
Q

formed in concrete due to many reasons, but when these ruptures are very deep, it is unsafe to use that concrete structure.

A

Cracks

43
Q

Various reasons for fissures and improper mix design, insufficient curing. omission of expansion and contraction joints, use of high slump concrete mix, unsuitable sub-grade etc.

A

Cracks

44
Q

also called as pattern cracking or map cracking, is the formation of closely spaced shallow cracks
in an uneven manner.

A

CRAZING

45
Q

occurs due to rapid hardening of the top surface of concrete due to high temperatures if the mix contains excess water content or due to insufficient curing.

A

CRAZING

46
Q

is the formation of hollow bumps of different sizes on the concrete surface due to entrapped air under the finished concrete surface.

A

BLISTERING

47
Q

It may be caused by excessive vibration of the concrete mix, or presence of excess entrapped air in a mix, or improper finishing.

A

BLISTERING

48
Q

is also similar to blistering. In this
case also, the top surface of the concrete gets separated from the underlying concrete.

A

DELAMINATION

49
Q

Hardening the top layer of concrete
before the hardening of the underlying concrete will lead to this defect.

A

DELAMINATION

50
Q

It is because the water and air bleeding
from underlying concrete are struck between these two surfaces, hence space will be formed.

A

DELAMINATION

51
Q

also called as chalking, is the formation of fine and loose powdered concrete on the hardened
concrete by disintegration.

A

DUSTING

52
Q

This happens due to the presence of excess amount of water in concrete.

A

DUSTING

53
Q

It causes the bleeding of water from concrete, with this, fine particles like cement or sand will rise to the top, and consequent wear causes dust at the top surface.

A

DUSTING

54
Q

When a concrete slab is distorted into a curved shape by upward or downward movement of edges or corners,

A

CURLING

55
Q

It occurs mainly due to the differences in
moisture content or temperature between slab surface (top) and slab base (bottom).

A

CURLING

56
Q

is the formation of deposits of salts on
the concrete surface. Formed salts are generally white in color. It is due to the presence of soluble salts in the water which is used in making concrete mix.

A

EFFLORESCENCE

57
Q

in both the cases, concrete surface gets deteriorated and flaking of concrete occurs. The main cause for this type of cases is penetration of water through concrete surface. This makes steel gets corroded and it may
occur.

A

SCALING AND SPALLING

(Construction Materials 101) (12 decks)

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