Quantification of the CO2 binding capacity of reinforced concrete is of high importance for predicting the carbonation potential and service life of these structures. Such information is still not available for alkali activated materials that have received extensive attention as a sustainable substitute for ordinary Portland cement (OPC)-based concrete. To address this gap, this paper evaluates the CO2 binding capacity of ground powders of alkali activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes under accelerated carbonation conditions (1 % v/v CO2, 60% RH, 20°C) for up to 180 days. The CO2 binding capacity, the gel phase changes, and the carbonate phases are investigated with complementary TG-DTG-MS, FT-IR and QXRD techniques.Five mixtures with different FA/GBFS ratio are considered. CEM I and CEM III/B pastes are also studied to provide a baseline for comparisons. The results showed that the alkaliactivated pastes have a lower CO2 binding capacity in comparison to cement-based pastes. Furthermore, alkali-activated pastes have similar CO2 binding capacity regardless of the FA/GBFS ratio. It was observed that the silicate functional groups corresponding to the reaction products in the pastes were progressively changing during the first 7 days, after which only carbonate groups changed. It was also found that the CO2 bound in the alkali-activated pastes occurs to a substantial extent in amorphous form.
Mesozoic melilite-bearing ultrama®c lamprophyres are developed as sill, dyke and plug-like intrusive bodies in the East Antarctic Beaver Lake area. They consist of varying amounts of olivine, melilite, phlogopite, nepheline, titanomagnetite and perovskite as major phases, accompanied by minor amounts of apatite, carbonate, spinel, glass and, rarely, monticellite. The rocks are mineralogically and geochemically broadly similar to olivine melilitites, differing in higher CO 2 and modal phlogopite and carbonate contents. The ultrama®c lamprophyres are MgO-rich (13.4±20.5 wt%) and SiO 2 -poor (32.8±37.2 wt%), indicative of a near-primary nature. Major and trace element features are consistent with minor fractionation of olivine and Cr-spinel from melts originating at depths of 130±140 km.Primary melts originated by melting of upper mantle peridotite which had been veined by phlogopite carbonate clinopyroxene-bearing assemblages less than 200 Ma before eruption. The presence of the veins and their time of formation is required to explain high incompatible trace element contents and growth of 87 Sr= 86 Sr, leaving 143 Nd= 144 Nd unaffected. The major element, compatible trace element, and most radiogenic isotope characteristics are derived from melting of the wall-rock peridotite. The depth of about 130 km is indicated by the presence of phlogopite rather than amphibole in the veins, by control of the REE pattern by residual garnet, by the high MgO content of the rocks, and by the expected intersection of the rift-¯ank geotherm with the solidus at this depth. The higher CO 2 contents than are characteristic for olivine melilitites favoured the crystallization of melilite at crustal pressures, and suppressed the crystallization of clinopyroxene. The Beaver Lake ultrama®c lamprophyres are a distal effect of the breakup of Gondwanaland, too distal to show a geochemical signature of the Kerguelen plume. Upward and outward movement of the asthenosphere-lithosphere boundary beneath the Lambert-Amery rift led ®rst to the production of phlogopite-and carbonaterich veins, and later to the generation of the ultrama®c lamprophyres themselves.
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