Abstract
This study aims to investigate the feasibility of alkali activated slag as a sole binder for refractory concretes. The concrete samples prepared are subjected to different firing temperatures at 850, 1100 and 1300 degrees C. The mineralogical compositions of the fired concretes are investigated using x-ray diffraction (XRD), and the microstructure is 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) are tested. Variation in sintering parameters and mechanical properties is observed by changing firing temperatures. Refractory concretes based on geopolymers exhibit significant PLC only at 1300 degrees C, the maximum PLC index (0.56%) is observed under load and with an increase in temperature. In addition refractory concretes have a good TSR index (up to 15 cycles). According to XPAanalysis data within fired concretes apart from the main phases within aggregates, there are readily melting phases formed at 850 and 1100 degrees C. Apparently with an increase in temperature there is formation of hibonite and anorthite. A needle-shaped structure is noticed embedded in glassy matrix at 110 degrees C, but the plate-like structure of hibonite is observed at higher temperature. On the whole XPA results reveal that alkali activated slag cement is a promising binder for refractory concretes at high temperature.