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Concrete > Quiz 1 > Flashcards

Quiz 1 Flashcards

(54 cards)

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1
Q

Concrete ingredients

A

Cement, Aggregates, Water, Additives and addmixtures, cement paste.

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2
Q

4 types of rocks for Aggregates

A

Igneous, Sedimentary, metamorphic rocks, mineral constituents

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3
Q

3 Classification of Aggregates source

A

Smooth Uniform, Smooth Well-Graded, Rough Well-Graded

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4
Q

Rough Well-Graded achieve desired concrete qualities

A

Uniformity of Concrete Mixture, Durability of Concrete, Economic design

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5
Q

Coarse Aggregates sieves

A

1-#4

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6
Q

Fine Aggregates sieves

A

10-#100+Pan

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7
Q

CSA 5 types of Cement

A

10 (Normal Portland),
20 (Moderate Portland),
30 (High Early Strength Portland),
40 (Low Heat of Hydration Portland),
50 (Sulphate Resistance Portland)

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8
Q

Raw Mat. In Cement

A

Lime, Iron, Silica, Sulphate, Alumina

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9
Q

Additives and Addmixtures

A

Accelerators><Retarders,
Air Entraining Agents,
Superplasticizers,
Hardeners,
Water reducing admixtures,
Bonding Agents,
Coloring Agents,
Non-skid surface,
Surface sealing Agents

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10
Q

Mix Concrete Steps

A

1) Half of water+Coarse+Air Entraining Agents+Fine+Cement
2)Mix 30s
3) Add Half of water
4) Mix 3.5 mins
5)stop for 3 mins
6) Mix 1 mins

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11
Q

Mixing efficiency is reduced if

A

Blades are work out or coated with hardened concrete

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12
Q

Time between batching and complete discharge

A

2 hours

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13
Q

Mixing at high speed for long time can result in

A

Loss of strength, rises in temp., loss of entrained air, slump loss

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14
Q

Desirable properties of hardened concrete

A

Strength, Durability and good Appearance

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15
Q

Concrete should not be deposited in large piles and moved too long distance

A

To prevent segregation.

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16
Q

Concrete normally slump

A

3”-5”

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17
Q

Cold joints

A

A line or narrow band of Concrete of different colors

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18
Q

Compaction (Consolidation)

A

Process of vibrating freshly mixed concrete to reduce entrapped air

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19
Q

Compaction directly improves

A

Durability

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20
Q

Compaction achieve through

A

Rodding or vibrating

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21
Q

Vibrators for consolidation

A

Increase durability, density, homogeneity, strength, bond between structure joints and steel reinforcement.
Decrease permeability, entrapped air.
Eliminate voids, honeycomb, bug holes in concrete surface

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22
Q

Curing

Study These Flashcards
A

Applying moisture to surface of set/hardened concrete.

23
Q

Purpose of curing

Study These Flashcards
A

Maintain adequate moisture content in concrete for Hydration process to proceed unimpeded,
Control temp.

24
Q

Rate of Hydration depends on

25
Crazing
Uncured structural elements develop patterns of fine cracks. Cause low strength and little resistance to abrasion.
26
3 Curing methods
1) apply moisture to the surface -> replace evaporation 2) seal concrete -> prevent evaporation 3) both 1 and 2
27
Fogging
Apply a fine fog spray of water. Must be adjusted to prevent ponding of surface. Immediately after, followed by 7 days wet curing
28
Water spray
Only if concrete surface can be kept continuously damp. Otherwise cracking of surface.
29
Wet burlap
On concrete that has set. Presoaked by immersed in water 24 hrs before placing.
30
Strip of burlap
Overlap 150 mm and taped or weighted down around perimeter
31
Membrane curing
After burlap 7 days. Second application in 1-2 hrs after 1st.
32
Thermal curing
If temp. diff. between center of structure and outside is excessive -> insulated using blankets.
33
Finishing
Surface treatment of fresh or hardened concrete, slag or fly ashes
34
Lime
Limestone, shale, sandstone, clay, chalk, calcite
35
Iron
Iron ore, pyrite, shale
36
Silica
Sand, limestone, shale, sandstone, clay, quartz
37
Sulphate
Gypsum, calcium, sulphate
38
Alumina
Bauxite, clay, limestone, shale
39
Silica fume
Silicone, early strength, Enables early stripping of forms. 7-10% of cementitous mat. Improve cohesion, Prevent segregation
40
Voids
Major source of degredation
41
Water/Cement 0.3
7 days: 21 28 days: 42
42
Water/Cement 0.5
7d: 19, 28d: 34
43
W/C 0.7
7d: 15, 28d: 25
44
Retarders
Delay setting, Hot weather or long haul distance, may impede early strength development
45
Air Entraining Agents
Trapped controlled amount of air into the concrete, Improve workability, Resistance to frost action. Reduce water bleeding
46
Superplasticizers
Coat the cement particles Cause particles to repel each other, Allow concrete to flow easier-improve workability, Reduce water needed to make concrete workable, Add in the field (during mixing) before any slump loss can occur.
47
Hardeners
Increase Impact resistance and abrasion resistance, 2 forms: chemical additives, metallic aggregates
48
Bonding Agents
Enhance bonding New and old surfaces, Place metallic Aggregates agents on cleaned old surface before placing new concrete, Latex emulsions are also used-bonding new and old surfaces.
49
Accelerators
Speed up the initial setting of Concrete, Enhances early removal of formwork, Reduce the setting and curing period, Most common CaCl2 (deterioration of steel rebar)
50
Water Reducing Admixtures
Increase slump for a given water content, Retard setting time, Introduce entrained air, Increase drying and shrinkage, Testing should be done before use
51
Non skid surface
Surface Trowelled by a wood or cork float to provide rough surface, Use abrasive Aggregates as topping
52
Surface Sealing Agents
Decrease water loss during curing, Prevent passages of oil, grease and paint
53
Slag
Iron production
54
Fly Ash
Coal production, lower Hydration Temps, delay early strength development, Reduce risk of cracking, Improve long term properties, Improve ease of finishing

Concrete (1 decks)

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