Cement Flashcards

1
Q

How much of the C02 produced in the production of concrete comes from cement?

A

> 60% from modern concrete mixes
~25% comes from clinker substitution
80% for ordinary portland cement concrete

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2
Q

What reaction takes place in the production of early forms of cement?

A

Lime reactions:
Calcinning calcium carbonate at ~700-900 C
(there is more info on slide 10 lecure 6)

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3
Q

What are the 3 main stages of lime reactions

A
  1. Calcium carbonate -> Lime
  2. Quicklime + water –> portlandite
  3. Portlandite hardens with CO2
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4
Q

Name the main types of Hydraulic Inorganic Calcareous cements

A

Portland, Calcium aluminate, Pozzolaic, hydrophobic, Natural, expanding

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5
Q

Name the main types of non-hydraulic inorganic calcareous cements

A

Limes, Gypsum cements and plasters

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6
Q

What is the process for the production of odinary Portaland cement (OPC, ‘CEM 1’)

A
~75% limestone or chalk +
~25% clay or shale
--> Heat to 1450 C
--> Forms clinker 
--> Grind to powder
--> add ~4% gypsum
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7
Q

What are the 3 main types of cement for packaging and transport?

A
  • Ready-mix 47% of the market (6.2Mt)
  • Precast 22% (2.8Mt)
  • Retail 13% (2.4Mt)
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8
Q

How is ready-mix concrete used?

A

Concrete is mixed and poured on site

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9
Q

How is precast concrete used?

A

Product is manufactured off-site and tranported to site

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10
Q

How is retail cement used?

A

must be mixed and poured on site, comes in a dry bag, small scale uses

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11
Q

What is a Supplementary cementitous material (SCM)

A

Any reactive non-clinkered solid material used in cement (not including admixtures with special functions such as gypsum)

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12
Q

What is cement clinker blended with?

A

A source of calcium sulphate (e.g. gypsum) and SCMs

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13
Q

Give a few examples of SCMs

A
  • finely ground limestone
  • coal fly ash
  • granulated blast furnace slag
  • calcined clay
    (pictures on slide 25 lecture 6)
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14
Q

When are SCMs added?

A

Either at the cement plant when limestone is added or at the concrete batching plant, this is dependent on cost

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15
Q

What is capillary porosity?

A
  • The space not filled by hydration pores
  • 0.05 - 10 um in diammeter
  • Influence strength and durability
  • Determine transport properties in cement paste
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16
Q

What pore humidity is needed to ensure hydration

A

> 80%, but it is slow blow 90% relative humidity

17
Q

What ratio of cement to hydration products occurs

A

1 unit of cement goes to 2.2 units of hydration products

18
Q

What does C-S-H stand for

A

Calcium Silicate hydrates

19
Q

What is the water to cement ratio (w/c) for high performance concrete

A

0.3

20
Q

What is the water to cement ratio (w/c) for structural concrete

A

0.45

21
Q

What is the water to cement ratio (w/c) for low performance (e.g. garden path) concrete

A

0.6

22
Q

What are the main phases of portland cement

A

Alite (C3S), Belite (C2S), aluminate (C3A), and ferrite (C4AF)

23
Q

Name some cement binder types

A
  • Portland cement binder (CEM I)
  • Blended (Portland) cement binders (CEM II-V LC^3)
  • Reactive belite Portland cement binder (RBPC)
  • Belite y’elemite - ferrite cement binder
  • Calcium sulfoaluminate cement binder (CSA(B))
  • Supersulfated Cement binder
    (more on slide 52 lecture 6