Luukkonen Tero, Yu Yangmei, Adhikary Suman Kumar, Kauppinen Sami, Finnilä Mikko, Perumal Priyadharshini
Fibre and Particle Engineering Research Unit, University of Oulu, Oulu, Finland.
Research Unit of Health Sciences and Technology, University of Oulu, Oulu, Finland.
R Soc Open Sci. 2024 Aug 21;11(8):240598. doi: 10.1098/rsos.240598. eCollection 2024 Aug.
Porous alkali-activated materials are synthetic aluminosilicates that should be often produced as granules for practical applications. In the present study, municipal solid waste incineration fly ash with ~1.2 wt% of metallic aluminium was used as a novel blowing agent for metakaolin (their ratio ranged from 0% to 100%) with an aqueous sodium silicate solution as the alkali-activator and granulation fluid in high-shear granulation. The compressive strength of all granules was sufficient (≥2 MPa). Water absorption indicated an increase in porosity as the fly ash content increased. However, X-ray microtomography imaging showed no clear correlation between the fly ash content and porosity. The granules exceeded the leaching limits for earth construction materials for antimony, vanadium, chloride and sulphate. Of those, antimony, chloride and sulphate could be controlled by decreasing the ash content, but the source of vanadium was identified as metakaolin. The increase in the fly ash content decreased the cation exchange capacity of the granules. In conclusion, the recommended fly ash content is equivalent to 0.3 wt% of Al and the developed granules could be best suited as light-weight artificial aggregates in concrete where the additional binder would provide stabilization to decrease the leaching.
多孔碱激活材料是合成铝硅酸盐，在实际应用中通常制成颗粒状。在本研究中，以含有约1.2 wt%金属铝的城市固体废弃物焚烧飞灰作为偏高岭土的新型发泡剂（其比例范围为0%至100%），以硅酸钠水溶液作为碱激活剂和高剪切造粒中的制粒流体。所有颗粒的抗压强度都足够（≥2 MPa）。吸水率表明随着飞灰含量的增加孔隙率增大。然而，X射线显微断层成像显示飞灰含量与孔隙率之间没有明显的相关性。这些颗粒中锑、钒、氯和硫酸盐的浸出量超过了土建材料的浸出限值。其中，锑、氯和硫酸盐可以通过降低飞灰含量来控制，但钒的来源被确定为偏高岭土。飞灰含量的增加降低了颗粒的阳离子交换容量。总之，推荐的飞灰含量相当于0.3 wt%的铝，所研制的颗粒最适合作为混凝土中的轻质人工骨料，其中额外的粘结剂将提供稳定性以减少浸出。
