Experimental study on CO2 sequestration performance of alkali activated fly ash and ground granulated blast furnace slag based foam concrete

In an effort to reduce the emission level of carbon dioxide (CO2) from metallurgical, thermal, cement burning and other enterprises, an innovative solution is proposed in this study, which aims to sequester CO2 with alkali activated fly ash (FA) and ground granulated blast furnace slag (GGBFS) based foam concrete. The fluidity of alkali activated foam concrete (AAFC) fresh paste, dry density and compressive strength after hardening, micro-pore structure, carbonation products and CO2 sequestration capacity were comprehensively explored. The experimental findings indicated that the fluidity of AAFC slurry was almost unaffected by the content of foaming agent hydrogen peroxide (H2O2). When the H2O2 content ranges between 1 % and 3 %, the dry density of uncarbonated AAFC ranges approximately 752.3-365.2 kg/m(3), and the compressive strength of carbonated AAFC ranges about 1.01-0.21 MPa. Accelerated carbonation increased the dry density of uncarbonated AAFC samples. The porous structure of AAFC facilitated CO2 gas penetration into the matrix, leading to rapid carbonation. When the H2O2 content was 1 %, the compressive strength of fully carbonated AAFC was lower than that of non-carbonated AAFC; however, when the H2O2 content exceeded 1.5 %, the trend in compressive strength reversed. The carbonation kinetics of AAFC demonstrated a linear relationship with the square root of carbonation time, and the carbonation coefficient increases proportionally with H2O2 content. The porosity of AAFC increased from 61.05 % to 71.51 % as the H2O2 content increased from 1 % to 2.5 %. The main pore size distribution range of AAFC was 30-400 mu m and 5-50 nm. Accelerated carbonation minimally impacted the total porosity of AAFC but transformed certain large pores into capillary pores. Accelerated carbonation would generate calcite, aragonite, vaterite and additional amorphous phases. The maximum carbon sequestration capacity of AAFC, as determined in this study, reached 26.41 kg/m(3), indicating significant potential for CO2 sequestration.