Evolution of phase assemblage of blended magnesium potassium phosphate cement binders at 200° and 1000°C

The fire performance of magnesium potassium phosphate cement (MKPC) binders blended with fly ash (FA) and ground granulated blast furnace slag (GBFS) was investigated up to 1000 degrees C using X-ray diffraction, thermogravimetric analysis and SEM techniques. The FA/MKPC and GBFS/MKPC binders dehydrate above 200 degrees C to form amorphous KMgPO4, concurrent with volumetric and mass changes. Above 1000 degrees C, additional crystalline phases were formed and microstructural changes occurred, although no cracking or spalling of the samples was observed. These results indicate that FA/MKPC and GBFS/MKPC binders are expected to have satisfactory fire performance under the fire scenario conditions relevant to the operation of a UK or other geological disposal facility.