Portland Cement (extra)

Question 1

what are the three main raw materials of PC cement?

Answer 1

• lime CaO
• silica SiO2, alumina Al2O3
• gypsum CaSO4

Question 2

what do the three main raw materials of PC form? what is it called?

Answer 2

clinker

Question 3

what does the C notation mean?

Answer 3

CaO

Question 4

what does the S notation mean?

Answer 4

SiO2

Question 5

what does the A notation mean?

Answer 5

Al2O3

Question 6

what does the F notation mean?

Answer 6

Fe2O3

Question 7

what does the H notation mean?

Answer 7

H2O

Question 8

what does the Š notation mean?

Answer 8

SO3

Question 9

what is the reaction for stage 1 (alite phase)?

Answer 9

2C3S + 6H —> C3S2H3 + 3Ca(OH)2

Question 10

what is the reaction for stage 2 (belite phase)?

Answer 10

2C2S + 4H —> C3S2H3 + Ca(OH)2

Question 11

what is the reaction for stage 3 (tricalcium alumninate phase)?

Answer 11

C3A + 6H —> C3AH6

C3A + 3CŠ.2H + 26H —> C6AŠ3H32 (ettringite)

Question 12

what is the reaction for stage 4 (calcium alumino ferrite phase)?

Answer 12

C4AF + calcium hydroxide + gypsum + water —> solid solution of sulfoaluminate & sulfoferrite

Question 13

which stage is faster, alite or belite?

Answer 13

alite is FAST

belite is SLOW

Question 14

what is the alite phase responsible for?

Answer 14

early, initial strength

Question 15

what is the belite phase responsible for?

Answer 15

long term strength

Question 16

why is gypsum added in stage 3?

Answer 16

added to slow the rate of reaction, stage 3

Question 17

what product of the hydration reactions is the main source of the concrete’s strength?

Answer 17

C-S-H gel

Question 18

where is most of the C-S-H gel formed, in the alite or belite stage?

Answer 18

the alite stage

Question 19

what happens in stage 3 (general)?

Answer 19

• produces rapid setting “flash set”
• high heat of hydration
• ettringite and then monosulfate form
• ettringite = rod like crystals
• monosulfate usually replaces ettringite

Question 20

what stage gives concrete its characteristic grey colour?

Answer 20

stage 4

Question 21

what are the pozzolanic reactions?

Answer 21

S + CH + H —> C-S-H

AxSy + mCH + nH —> C-S-H + C-A-H