Mechanism of Carbonation of Mortars and the Dependence of Carbonation on Pore Structure

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Title: Mechanism of Carbonation of Mortars and the Dependence of Carbonation on Pore Structure

Author(s): Li Ying-Up and Wu Qiu-Dong

Publication: Special Publication

Volume: 100

Issue:

Appears on pages(s): 1915-1944

Keywords: blended cements; calcium carbonates; carbonation; concretes; diffusion; fly ash; kinetics; mortars (material); porosity; portland cements; portland pozzolan cements; General

Date: 4/1/1987

Abstract:
Discusses natural and artificial carbonation of mortar and concrete. The theoretical analyses and experimental results show that in both cases the mechanism of carbonation of mortar or concrete is the same. They are comparable when CO2 diffuses in the gas phase, the carbonation coefficient equation is Q = a1(2C1 / KP)«. The experimental results also indicate that the pores with radii over 320 A have a great effect on the diffusion coefficient, and the following relation holds: ln a1 = 105.66Ec - 0.877 where Ec is the volume of these pores divided by the total volume of the system. The results point out that there are some active sites on pore walls where CaCO3 first nucleates and the Ca++ near the pore moves toward these sites as the CaCO3 crystals grow.