Concrete Mix Design for Service Life of RC Structures under Carbonation Using Genetic Algorithm

Table 1

Influencing parameter on carbonation behavior.

Internal parameter; (mixture)	Low w/c and large unit cement amount	(i) Holding pH in alkali through producing large amount of hydration of CSH and Ca(OH)2; (ii) Low CO2 diffusion through dense pore structure
	Aggregate	CO2 intrusion through artificial light weight aggregate
	Mineral admixture; (slag and fly ash)	(i) Small amount of Ca(OH)2 due to pozzolanic reaction and latent hydraulic reaction
		(ii) Low diffusion coefficient of CO2
	Mixed chloride content	Rapid carbonic reaction due to high pH from ion dissociation
	Alkali	(i) Rapid carbonic reaction due to high alkali cement
		(ii) Residual metallic oxide (K2O, Na2O)
External parameter	CO2 concentration	Rapid carbonation through higher concentration of CO2
	Temp.	Increasing activity energy due to high temperature  (Arrhenius law)
	R.H.	(i) Decreasing carbonation in low R.H. due to insufficient H2O
		(ii) Decreasing carbonation in high R.H. due to low CO2 diffusion
	Induced chloride ion	Rapid carbonation due to dissociated chloride ion (cation)