Estimation of Depth of Concrete Carbonation


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Title: Estimation of Depth of Concrete Carbonation

Author(s): R. H. Zhang, T. Nakazawa and F. lmai

Publication: Special Publication

Volume: 170


Appears on pages(s): 633-648

Keywords: Carbonation; concretes; diffusion; humidity; size distribution.

Date: 7/1/1997

An analytical expression for estimation of the depth of concrete carbonation is derived by considering that carbonation is controlled by dif-fusion of CO2 in concrete. The depth of concrete carbonation with time is given simply iii terms of the diffusion coefficient of CO2 iii concrete: con-centrat ion of ambient CO2, a n d concent rat ion of carbonat able CaO in the hydration products of cement iii concrete. The diffusion coefficient of CO2 in concrete, which is a function of the volume of empty pores iii concrete, is described and suitably modified. The given expression provides a good explanation for the relationship be-tween the depth of carbonation and the internal microstructure of concrete. The estimated results are compared with some available experimental data and the results of carbonation of a 39-year-old concrete bridge. The expression shows good reliability.