Chemistry Of Cement

Question 1

Cement manufacturing process

Answer 1

1) excavation and crushing: limestone and clay are excavated from mines and crushed into small pieces
2) Blending and grinding: the crushed materials of a ground into fine powder and mixed together
3) Burning of the raw material: the mixture is preheated and then heated in a rotary King at 1,4 00 to 1,500° c to form clinkers
4) Cooling and grinding:The clinker is cooled down , mixed with gypsum and grounded into fine powder in a rotating drum with steel balls
5) Storage and Packaging: the cement is stored in a silo and then packages in bags(50kg) or supplied in box bulk

Question 2

what are the form major reaction components in cement

Answer 2

dicalcium silicate (C²S)
tricalcium silicate (C³S)
tricalcium aluminate(C³A)
tetracalcium aluminate(C⁴AF)

Question 3

Stages of hydration reaction

Answer 3

Stage 1: Fibers start forming (0 to 45min).The mixture is still easily workable for shaping and pouring

Stage 2: Fibers continue to grow and start to interlock(45 min to 2hrs)The , mixture becames less workable

Stage 3: Fibers interlock,the mixture has set(2 to 4 hrs).The mixture is non-workable

Question 4

gypsum

Answer 4

it is added to prevent the cement from rapid settling how it works is that when water is added did Gibson react with try calcium aluminate to form ettringite

Question 5

types of extenders

Answer 5

Ground Granulated Blast Furnace Slag (GGBS)
Fly-ash (FA)
Condensed Silica Fume

Question 6

Explain Ground Granulated Blast furnace

Answer 6

One by-product of iron extracted from iron ore, it will become hot slag that that will be left behind and would rapidly quickly cool down and ground into fine powder
Hydrates to forming cemental compounds when mixed with water and active by high pH from Portland cement

Question 7

Explain fly Ash

Answer 7

By-product of coal in fumes
Reacts with calcium hydroxide in water to form cementing components known as pozzolan

Question 8

Explain l condensed silica fume

Answer 8

By-product of silicon and ferosilicon alloys
made from a reaction between quartz and coal in electrical arc furance
Reacts with calcium hydroxide in cement to form cementio components

Question 9

dicalcium silicate (C²S) Properties and roles

Answer 9

Slow strength gain
Responsible for long-term strength

Question 10

tricalcium silicate (C³S) Properties and roles

Answer 10

Rapid strength gain
Responsible for early strength (7 day)

Question 11

tricalcium aluminate(C³A) Properties and roles

Answer 11

Quick setting (controlled by gypsum)
susceptible by Sulphate attack

Question 12

tetracalcium aluminate(C⁴AF)Properties and roles

Answer 12

Little contribution to strength or setting
Responsible for grey colour of OPC

Question 13

tetracalcium aluminate(C⁴AF)Properties and roles

Answer 13

Little contribution to strength or setting
Responsible for grey colour of OPC