environment of concrete. Carbonation starts with the diffusion of
dissolved CO2 molecules in pore water of concrete and then the
formation of calcium carbonate with calcium hydroxide and calcium
silicate hydrates (C–H–S) [7,8]. The diffusion of CO2 in concrete
depends on a number of factors, such as CO2 concentration,
porosity and moisture content of the concrete. The carbonation
process starts at the surface and penetrates slowly to the interior
of the concrete and the depth of carbonation is considered to be
as one of the most important factors in assessing the durability
of concrete structures.