Carbonation

Question 1

Three processes in carbonation

Answer 1

Ingress of CO2 - diffusion/conc difference
Reduction of CO2 with alkali in pore fluids = carbonic acid
Formation of carbonates and neutralisation = bi carbonates , passivation of oxide layer

Question 2

Factors for carbonation

Answer 2

Humidity
Temp
CO2
Concrete properties

Question 3

What happens if humidity is too high/low

Answer 3

Low - lack of electrolyte. Electrons struggle to move through cover
High - too wet

Question 4

As CO2 increases, carbonation…..

Answer 4

Increases

Question 5

Three concrete properties that affect carbonation

Answer 5

Physical - W/C ratio decreases of cement increases causes a decrease in porosity and increase in tortuosity
Chemical: GGBS & fly ash increase ability for CO2 to move into pore fluids
Increase OH- (alkali)

Question 6

Ways to resist carbonation

Answer 6

Reduce pore size/distribution
Chemical - high alkaline
PC good
PFA, GGBS - low alkalinity - bad