碱活化粉煤灰制备高强膨胀陶粒及膨胀机理

以粉煤灰为原料,经碱液水热活化、挤压成型、煅烧制备了高强耐磨、吸水率低的膨胀型陶粒.采用SEM和XRD分析了材料的微观形态及晶相结构,考察了所得陶粒的基本性能,探讨了高强膨胀陶粒的制备机理.结果表明,粉煤灰的碱水热活化是高强膨胀陶粒形成的关键,生成的Na2SiO3使粉煤灰黏结成型导致了膨胀陶粒的生成,而且Na+诱导霞石生成,降低了陶粒的膨胀温度.NaOH浓度和焙烧温度越高,越易生成膨胀陶粒.在粉煤灰与NaOH溶液质量比为1∶1、NaOH浓度3mol/L、焙烧温度1000℃的条件下制备的膨胀陶粒性能最好.

Preparation of High-strength Bloating Ceramisite from Fly Ash Using Alkali Activation and Its Expansion Mechanism

Bloating ceramisite with high strength and low water absorption has been successfully prepared from fly ash via hydrothermal activation in alkali solution followed by extrusion moulding and calcination.The morphology and crystal structure of samples were analyzed with SEM and X-ray diffraction instruments.The properties and expansion mechanism of ceramisite were also investigated.The key preparation procedure of bloating ceramisite was the alkali hydrothermal activation of fly ash,resulted in producing Na2SiO3 which play an role of binder in the formation of bloating ceramisite.The bloating temperature of ceramisite was reduced for the formation of nepheline in the presence of Na+.Higher calcination temperature and NaOH concentration were benefited for the preparation of bloating ceramisite.The optimized preparation conditions were liquid / solid(NaOH solution / fly ash mass ratio) 1∶1,NaOH concentration 3 mol/L,and calcination temperature 1000 ℃.