CO₂ Mineralization Of Fly Ash-based Filling Materials And Water Chemistry Environmental Impact Assessment

With the status of long-term high solid waste and CO₂ emissions,as well as the continuous expansion and deepening of research on physicochemical properties and derived applications of various solid waste based filling materials,how to realize solid waste utilization and CO₂ storage on the premise of not damaging the ecological environment has become a top priority.The organic combination of the two has multiple meanings of economy,energy saving and environmental protection,and promotes the development of environment-friendly materials that reduce pollution and carbon.In this thesis,laboratory test,theoretical analysis,site investigation and other methods are adopted,and materials such as Fly Ash,FA,Slag,S,cement,coal gangue and alkali activator are utilized.The mineral composition,compressive strength and microstructure of two kinds of Fly Ash base filling materials were analyzed by means of X-ray diffractometer（XRD）,press,scanning electron microscope and energy dispersive spectroscopy（SEM-EDS）.The fly ash-based Geopolymer was found by comparison.The mechanical properties of FAG are better than those of Fly Ash-based Binder Materials（FABM）.By studying the evolution of physical and chemical properties before and AFter mineralization with CO₂ in a closed environment,the mineralization mechanism was further analyzed,and the two groups of specimens with the best mechanical properties were selected for comparative calculation of mineralization amount and mineralization efficiency.Combined with the basic information of the mining area and on the basis of mastering the current water quality data,the leaching test was carried out on the above two groups of specimens,and the water chemical environmental impact assessment was carried out on their application.The research results are as follows:（1）Through macro and micro tests,it is found that FAG has better mechanical properties by comparing the physical and chemical properties of two kinds of fly ash based filling materials;The evolution of physical and chemical properties of FAG before and AFter CO₂ mineralization was studied,and the optimal ratio of mechanical properties was selected,with the highest compressive strength of 24.23MPa.（2）Master the whole reaction process,which mainly involves the hydration of the initial cement and FA,during which hydration products such as Calcium Hydroxide（CH）and Ettringite（AFt）are consumed to form calcite（Ca CO₃）;Then,the geological polymerization of"dissolvation-reconfiguration and polycondensation"was performed to produce calcium silicate aluminate hydrate（C-A-S-H gel）and sodium silicate aluminate hydrate（N-A-S-H gel）.Finally,with CO₂ entering the reaction system,Ca CO₃is generated by mineralization reaction.The mineralization amount of group 28d-10-64and group 28d-15-64 was 0.422 and 0.438 mg/g FAG,respectively,and the mineralization efficiency was 2.42%and 2.61%,respectively,by TG-DTG.（3）Taking a mining area in Jiangsu Province as the engineering application background,the water environment status evaluation was carried out;The above two groups of specimens were used for leaching test,and the analysis found that the other evaluation indexes were all within the standard range,and the overall water quality was good,except for the phenomenon of Fe ion exceeding the standard.