CIVL3360 CT

what is concrete

cement (9 -15%), water/air (15-16%), fine aggregate, coarse aggregate

paste

cement and water

mortar

paste and fine aggregate

concrete

mortar and coarse aggregate

cement manufacture

1.      Quarrying raw materials

2.      Crushing

3.      Prehomogenization and raw meal grinding

4.      Preheating

5.      Precalcining

6.      Clinker production in rotary kiln

7.      Cooling and storing

8.      Blending

9.      Cement grinding

10.  Storing in cement silo

portland cement

4 key componenets of cement

alite C3S, belite C2S, aluminate C3A, ferrite C4AF

C3S

hardens quickly with evolution of heat (high early strength),

constitutes 50-70% of portland cement clinker,

responsible for intial set

500 HoH

C2S

hardens slowly (later age strength after 7 days),

constitutes 15-30% clinker

250 HoH

C3A

reacts quickly with water(flash setting),

responsible for early setting and strength gain

aids in lowering clinker temp (combination of lime and silica) 850 HoH

C4AF

reacts quickly, minimal contribution to strength, presents in small amounts is the reason grey colour in concrete, acts as flux agent to reduce clinkering temp (iron)

why is gypsum important

to control the flash setting of C3A, improve shrinkage and strength development properties, 4-6% added

cement types

normal, high early strength, low heat, sulphate resisting

high early strength concrete

increase the amount of C3S (high early strength), reduce amount of C2S also grind it finer

low heat

reduce components with high HoH - C3A and C2S, blend with SCMs

sulphate resisting

reduce C3A as it is prone to sulphate attacks

C-S-H

calcium silicate hydrate, also known as gel, product of C3S and C2S reaction with water

fly ash

silica fume

ground granulated blast furnace slag