Modification of multi-source industrial solid waste with porous materials to produce highly polymerizeosilica gel: Microstructure optimization and CO2 mineralization enhancement mechanism

Abstract

The combination of solid waste into lightweight aggregates is a promising strategy for solid waste resource utilization and an effective method for carbon reduction. Herein, the lightweight aggregate with high CO2 adsorption and mineralization performance was prepared by multi-source solid waste combined with porous structural material. Based on the basic property parameters (density, water absorption and porosity) of lightweight aggregates, the effectiveness of multi-source solid waste (fly ash (FA), desulfurization gypsum (DG), coal gangue (CG), blast furnace slag (BFS) and steel slag (SS)) to improve the aggregate performance was determined. The water absorption rate reduced by 20 % and the mechanical strength increased by 49.1 % with the addition of five multi-source solid waste. Moreover, the amount of CO2 absorption could be steadily maintained above 20 % throughout the carbonization curing at room temperature. The decrease in bulk density and water absorption, as well as the increase in skeleton density and mechanical strength of aggregates, were the results of the synergistic effect of multi-source solid waste. This could be attributed to the correlation between the physical properties of the aggregate. The pathway of increasing carbon absorption was proposed based on product analysis and pore characterization. The inability of CO2 to diffuse into aggregate was referred to the accumulation of carbonate on the aggregate surface, resulting in a low carbon absorption rate. The porosity of aggregates was increased and the carbon absorption rate was improved by adding porous materials (diatomite and zeolite). The CO2 absorption of multi-source solid waste coupled with porous materials was increased to 26.3 % under 20 % CO2 (v/v) in nitrogen. Additionally, the synergistic effects of solid waste inhibited the content of heavy metals, and porous materials showed notable inhibiting effect on 8 heavy metals. Zn decreased by 28.7 % due to the addition of DE, and ZE had a better reduction effect by 42.9 %. This study provides a significant understanding of the porous materials modified cold-bonded aggregates by the utilization of multi-source industrial solid waste coupled with CO2 for building materials in engineering applications.