Preparation of alkali-activated slag based foam concrete and feasibility study on CO₂ sequestration

With the continuous advancement of industrialization process, the scale of industrial solid waste is also expanding. Foam concrete has great development potential in CO₂ sequestration. Therefore, it is of great significance for industrial solid waste for resource utilization and the economic and efficient storage of CO₂. In this paper, high-porosity foamed concrete is prepared using blast furnace slag as the raw material, NaOH as the alkali activator, sodium stearate as a foam stabilizer, and sodium dodecyl sulfate （C₁₂H₂₅NAO₄S, SDS） as the foaming agent. The influence of different NaOH content on the comprehensive performance of slag based foam concrete and CO₂ sequestration performance is investigated. The experimental results show that the dry density of foam concrete increases gradually with the increase of NaOH content. When the amount of NaOH is 12%, the compressive strength starts to decrease. The internal pore distribution of foam concrete is uneven, and the porosity is large. SEM results show that when the amount of NaOH is too high, the foam will break and connect, which will increase the proportion of macropores. XRD results show that the hydration products of slag based foam concrete are mainly C—S—H gel and Ht phase. The layered structure of Ht phase makes the pore wall of the material not dense enough, thus affecting the mechanical properties of the material. TGA results show that the hydrated products can effectively absorb CO₂ and transform it into carbonate dominated by CaCO₃. When the amount of NaOH is 12%, the maximum sequestration capacity of CO₂ is 89.74 kg/m³.