Cement Flashcards by Mark Ivanov

What is the difference between hydraulic and non-hydraulic cements?

Hydraulic cemented set when mixed with water

Non-hydraulic cements harden using CO2

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Portland cement is which type of cement?

Hydraulic

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Describe the production of Portland cement

~75% limestone or chalk
+
~25% clay or shale

Heat to ~1450C°

Forms clinker(silicates & aluminates)

Grind to powder

Add ~4% gypsum

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Why is sea water not good for concrete production?

Seawater contains high chloride concentration, which induces steel corrosion

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Lime is produced by heating []
CaCO3 > caO + CO2

Calcium carbonate

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Quicklime is mixed with [] to form []
CaO+H2O > Ca(OH)2

Water to form Portlandite

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Slaked lime harden by reacting with []
Ca(OH)2 + CO2 > CaCO3 + H2O

CO2

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Hydraulic or non-hydraulic?

Portland

Hydraulic

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Hydraulic or non-hydraulic?

Calcium aluminate

Hydraulic

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Hydraulic or non-hydraulic?

Pozzolanic

Hydraulic

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Hydraulic or non-hydraulic?

Hydrophobic

Hydraulic

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Hydraulic or non-hydraulic?

Natural

Hydraulic

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Hydraulic or non-hydraulic?

Expanding

Hydraulic

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Hydraulic or non-hydraulic?

Lime cements

Non-hydraulic

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Hydraulic or non-hydraulic?

Gypsum

Non-hydraulic

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Hydraulic or non-hydraulic?

Cements and plasters

Non-hydraulic

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5600BC

Yugoslavian huts made of lime (caO)

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Yugoslavian huts made of caO/lime

5600BC

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2500BC

Great pyramids of Giza limestone CaCO3

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Great pyramids of Giza limestone CaCO3

2500BC

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500BC

Lime and sand used for weak mortars in Greece

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Lime and sand used for weak mortars in Greece

500BC

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300BC-500AD

Romans mistook pozollan for sand, made better concretes with lime and ash

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Romans mistook pozollan for sand, made better concretes with lime and ash

300BC-500AD

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500-1756

Weak, slow setting cements used

500-1756

1759

Eddystone lighthouse is built using hydraulic lime

1759

1824

“Portland cement” made from limestone + fine clay heated to 1200°C

1824

Present day

Improved formation of calcium silicates, mainly belite (C2S) and also alite (C3S) Increased formation of alite as standard in PC clinker

Present day

What are the main calcium silicates and calcium aluminates found in cement clinker?

Alite C3S brown (ass-lite, brown shit) Belite C2S (beta-two) blue Aluminate C3A grey Ferrite C4AF white

What does SCM stand for?

Supplementary cementitious material

What are SCMs?

Anything that is added to cement that is non-clinkered (at the end of production)

Name some SCMs

Gypsum (main one) Coal fly ash Granulated blast furnace slag Gypsies throwing coal at slags

In the rotary kiln, what is the dominant phase in the beginning?

Limestone

In the rotary kiln, what is the dominant phase in the middle?

Lime and belite

In the rotary kiln, what is the dominant phase in the end?

Alite

Concrete and belite continue to [] up to [] after hardening is done

React up to 180 days

Hydration products are [] than clinker

Less dense

What does production of hydration products do to cement?

Cause volume changes, as they are less dense

1 unit vol Clinker = what unit vol of HP? HP = hydration products

2-4

PC + water gives us a

Plastic, workable paste before the initial set

After the initial set we get a

Stiff,workable paste

After the final set we have a

Rigid solid, strengthens over time

What happens in day one of setting

Massive loss of fluidity, delayed increase of hydration product making and strength

What is the purpose of gypsum?

Added to PC to delay initial loss of fluidity

What happens after day 1 through to 1 year of setting?

Hydration product numbers increase slowly along with strength

Cement is available in:

Ready mix- poured on site Precast (OSM) Retail - bagged for various uses

What is a capillary pore?

Space not filled by hydration products

What is the diameter of a typical capillary pore?

0.5-10 micrometers

What is special about capillary pores?

They directly influence strength and durability of the concrete They determine transport properties in paste

Clay is in [], when it gets [] it expands

Clay is in layers When it gets wet it expands

C-S-H is the same as clay with how it can []

Expand

C-S-H sheets have

High porosity Large surface area

SCMs are [] reactive than [] with water

Less reactive than clinker

How can SCM reactivity be increased?

By making a more alkaline cement solution in what is called alkali activation

What are the pros of alkali-activated materials?

Faster setting and strength development Heat resistant Better thermal expansions

What are the cons of alkali-activated materials?

Prone to shrinking + cracking Activator expensive + environ impacts Steel corrosion chemistry differs High pH solutions are a safety concern

Cement Flashcards

(60 cards)