Evolution of pH Value of the Pore Solution after Realkalisation of Carbonated Concrete
A.Gerdes
F.H.Wittmann
Abstract：Method for realkalisation of carbonated concrete is based on the electrochemicalprocesses. In order to increase the pH value of pore solution the concrete is impregnated withalkali carbonates solutions. These buffer solutions should stabilize the pH value of pore solu-tion at a level higher than 10. However, analyses of impregnated concrete in practice showthat the pH value drops to values below 10 although sufficient alkali (Na+ , K+ , Li+ ) con-centration was available in pore solution. Experiments were carried out to confirm a hypothe-sis to explain the time-dependent decrease of the pH value. It is concluded that in the pres-ence of dissolved sulfates even a comparatively high content of alkali carbonates is not suffi-cient to maintain pH value higher than 10. The chemical mechanisms suggested in this paperare used to explain observations of practical applications. The complex interactions of dis-solved ions in pore solution have hardly been taken into consideration of the development ofnew technologies for realkalisation up to now. For this reason, the methods for realkalisationof carbonated concrete as discussed in this paper cannot be recommended.
Keywords：concretecarbonateelectrochemical realkalisationpore solutionpH value
Publication Date：2003-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：7( 111-117 )