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| We investigate the fast-reaction asymptotics for a reaction-diffusion (RD) system describing the penetration of the carbonation reaction in concrete. The technique of matched-asymptotics is used to show that the RD system leads to two distinct classes of sharp-interface models, that correspond to different scalings in a small parameter $\epsilon$ representing the fast-reaction. We explore three conceptually different scaling regimes (in terms of the small parameter $\epsilon$) of the effective diffusivities of the driving chemical species. The limiting models include one-phase and two-phase generalised Stefan moving-boundary problems as well as a nonstandard two-scale (micro-macro) moving-boundary problem -- the main result. |
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