Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Materials > Concrete > Flashcards

Concrete Flashcards

1
Q

What are the Properties in the Strength Development of Concrete ( CAWCCTT)

A

Cement Type
Admixtures
w/c ratio
Compaction
Curing
Temperature
Age

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the Poissons ratio for concrete

A

0.15-0.20

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 4 factors that cause creep in hardened concrete ( think soil creep )

A

Humidity
W/c ratio
Cement content
Stress

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why does drying shrinkage occur

A

Due to loss of moisture through evaporation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How can drying shrinkage be controlled

A

Reducing movement
Adding cement
Reinforced details
Movement joints

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does shrinkage drying cause to hardened concrete

A

Excessive cracking

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

List what is drying shrinkage dependent on ?

A

Humidity
Tempeture of surrounding air
Ratio of surface area to volume of concrete
Rate of air flow
Water and cement content
Curing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is thermal movement and why does it occur ?

A

The expansion and contraction of concrete due to the temperature change of heating and cooling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does cooling cause in thermal movement in concrete and why

A

Cooling can cause cracking if restrained due to daily/seasonal temperature change and heat of hydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What can heating cause in thermal movement

A

Can cause the steel within concrete to start buckling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the equation for expansion of material due to heating

A

LΔ = LxaxΔT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the difference between diffusion and permeability in the durability of concrete

A

Diffusion involves the change in concentration of a liquid/gas, while permeability involves the flow of a liquid/gas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Evaporation/absorption is dependent on what in hardened concrete

A

RH
Ambient Temperature
Wind
Surface characteristics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What types of deterioration ( loss of function over time ) is there for each material

A

Timber : wet/dry loss of strength
Concrete: sulphate or acid attack
Steel: formation of rust in the presence of oxygen and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is concrete carbonisation and how fast is it

A

Carbon dioxide neutralises with calcium hydroxide, if reaction reaches reinforcement in concrete corrosion will occur.
Very slow, depending on diffusion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What type of process is Chloride attack on reinforcements steel

A

A slow process depending on the surface absorption and diffusion within the concrete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What causes a chloride attack on reinforcemed concrete

A

Seawater and de-icing salts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How do you reduce the chance of a chloride attack on reinforced steel occurring

A

Keep surface absorption as low as possible through compaction process and curing
Keep diffusion low using a low w/c ratio with alternative cement materials ( admixtures )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How does fire affect the durability of materials such as timber, steel, plastics and concrete

A

Timer: highly flammable and toxic ( char outside of thick members )
Steel: loss of strength rapidly at high tempeture
Plastics : highly flammable and toxic
Concrete: non flammable but can spall at high temp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the basic materials that make up concrete ( CAWAV )

A

Cement
Aggregates
Water
Admixtures
Voids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the different types of Portland cement

A

OPC - Ordinary
RHPC - Rapid Hardening
SR - Sulphate resistant
WPC - White

22
Q

What is the process of creating cement

A

1 Rock materials of limestone, silica, shale, iron oxide are quarried
2 Rocks are then crushed into smaller rocks
3 Rock material is then mixed and run through a “ Rotary Kiln”
4 Rotary Kiln mixes Rock material and calines limestone - gets rid of CO2 - forming a clicker
5 clicker ground to a fine power and mixed with gypsum

23
Q

What are the alternatives to Portland Cement

A

GGBS ( Ground Gradulated Blast furnace Slag )
PFA ( Pulverised Fuel Ash )
Metakalin
Rice ash
Silica fume

24
Q

What is GGBS

A

By product of iron smelting
Carbon footprint of 35kg per tonne of CO2
Generally is blended up to 70% in OPC
Reduced early strength and early heat of hydration
Much lower carbon footprint

25
Q

What makes up cement hydration

A

W/c ratio is important for workability , strength and durability of concrete
Setting and hardening is a chemical reaction
This reaction is exothermic leading to “Heat of hydration”

26
Q

Explain the heat of hydration graph and Draw

A

Strength gain is initially rapid but slows down over time
Strength gain will occur indefinitely while moisture is present within concrete ( this is curing )

27
Q

What materials make up aggregates (3 materials)

A

Gravel, sand, crushed rocks

28
Q

What types of aggregated are there and what separates them

A

Coarse aggregate: cannot pass through a 5mm sieve
Fine aggregate : passes through a 5mm sieve

29
Q

How much do aggregate generally make up in a concrete mix

A

50-80%

30
Q

What are aggregates used for

A

Packing efficiently
Reduce spacing
Costs
Improving properties such as strength and drying shrinkage

31
Q

What are the requirement for aggregate?

A

Hard
Durable
Strength
Cleanliness ( no dust , chemical impurities and organic matter )

32
Q

What are the differences of densities in aggregates and what are they used for

A

Normal : gravel and crushed rocks
Lightweight : weak porous solid, thermal properties
High: radioactive screening

33
Q

What water is used in concrete and what is not allowed in it

A

Water must be free from impurities and potable
Must be free from (sugar sulphate chlorides)

34
Q

Name the types of admixtures there are

A

Water reducing
Air entraining
Superplasticisers
Self-compaction
Foamed

35
Q

What does the reducing water admixture do and how

A

Reduces the amount of water needed using plasticisers

36
Q

What does the air entraining admixture do

A

Evenly distributed air around concrete
Improves durability to marine and frost environments

37
Q

What does superplasticisers do ?

A

Allows for water removal , creating a higher strength

38
Q

What does self compacting admixtures do

A

Concrete doesn’t require compaction

39
Q

What does the foam admixture do

A

High flowing concrete with bubbles without any stones

40
Q

What factors affect the workability of fresh concrete

A

Water content
Fineness of cement
Aggregates
Grading
Admixtures
Time
Temperature

41
Q

What causes segregation in fresh concrete

A

Overhandling or vibration of concrete , or poor grading

42
Q

What is laitance

A

When coarse aggregate separates and sink to the bottom leaving cement paste on the top forming a scum on the surface of the concrete

43
Q

How do you reduce segregation

A

Increase air content
Increase rate of hydration
Reduce w/c ratio

44
Q

What is bleeding and what occurs

A

Bleeding is when water from the concrete comes to the surface of fresh concrete
Occurs when water is lighter than concrete, leaves pockets of low density in the concrete

45
Q

What are the 3 causes of bleeding

A

To much water
Poor grading of aggregates
Overworking concrete

46
Q

What is shrinkage

A

Shrinkage is when moisture moves from a high to low concentration in diffusion or air flow

47
Q

What is the cause of shrinkage and what happens

A

Moisture loss from the surface
Cracks form when the concrete is still young
Cracks form parallel to each other

48
Q

What increases evaporation which leads to shrinkage

A

Low RH
High surface temp
High wind speed

49
Q

How to minimize evaporation

A

Moist aggregates
Concrete cover
Plastic fibres

50
Q

How does honeycombing occur

A

Honeycombing occurs when void are left in concrete due to poor compaction not filling the spaces between the aggregates

51
Q

What is the definition of curing

A

Curing is the maintenance of satisfactory moisture content and temperature in concrete for a period of time

Materials (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions