Feasibility of alkali-activated materials as a binder for refractory castables

Abstract

This study aims to investigate the feasibility of alkaliactivated slag as a sole binder for refractory castables. The prepared castable samples were subjected to different firing temperatures at 850,1100 and 1300 °C. The mineralogical compositions of the fired castables were investigated using X -ray diffraction (XRD). The microstructure was examined using scanning electron microscope (SEM). Also, sintering parameters, mechanical properties as well as refractory properties in terms of permanent linear change (PLC), refractoriness under load (RUL) and thermal shock resistance (TSR) were tested. A variation in sintering parameters and mechanical properties is observed by changing firing temperatures. The geopolymer-based castables show a significant PLC only at 1300 °C, maximum expansion of 0,56 % under load and raising temperature and finally a good TSR up to 15 cycles. Phase analysis of fired castables confirmed, besides the main phases in aggregates, the formation of low melting phases at 850 and 1100 °C. Hibonite and anorthite were obviously observed with increasing the firing temperature. A needle-shaped structure is noticed embedded in glassy matrix at 110 °C, but plat-like structure of hibonite is observed at higher temperature. Overall, the results revealed that alkaliactivated slag cement is a promising binder for refractory castables at high temperature.