Carbonation of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes has been investigated after one year of exposure to 0.038 % (v/v) CO2 at 20°C, 55% RH. In particular, the aim was to study the gel deterioration in the samples and changes of the compositions and proportions of the individual chemical domains after carbonation. For that purpose, a new method called PhAse Recognition and Characterization (PARC) [1] based on SEM-EDS elemental mapping was used. The paste bulk chemical composition was evaluated with PARC and XRF. The crystalline products of carbonation were determined and quantified with X-ray diffraction (XRD). Local microanalysis shows that carbonation of the pastes was occurring predominantly around GBFS particles (carbonation of Ca-(Na-)Al-Si-H+Mg gel) and throughout the gel (carbonation of Ca-(Na-)Al-Si-H and Ca-(Na-)Si-H). @en

In this paper, PARC software was used to determine the spatial distribution of the dominant reaction products, their chemical composition and area/volume percentage in alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes. The pastes reacted at different rates and dominant compositional domains were Mg rich gel around GBFS particles, i.e. Ca-(Na-)Al-Si+Mg, while the domains further form the GBFS and FA particles consisted mainly of Ca-(Na-)Al-Si. The reaction degree of GBFS and FA was calculated. Alkali-activated GBFS reacted faster in the studied alkaline conditions, reaching 66 % reaction at 28 days as GBFS contains 99 vol.-% of highly-reactive calcium and magnesium-rich aluminosilicates. The reaction degree in alkali-activated FA and GBFS paste was lower, as FA contains 31 vol.-% of nonreactive phases (quartz, mullite, hematite). The results obtained from PARC were compared with independent bulk analytical techniques X-ray fluorescence (XRF) and X-ray diffraction (XRD).@en