Improved bonding properties of rectorite clay slurry after wet/dry grinding

Abstract Rectorite/kaolin clay slurry was used as a binder for unfired high alumina bricks, and the effects of dry/wet grinding on bonding performance of rectorite/kaolin clay slurry binders were considered. The clay slurries were characterized by particle size distribution, viscosity, electrophoretic mobility, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) before and after dry/wet grinding. It indicated that the rectorite clay slurry possesses a large particle size, high viscosity and good stability. After wet grinding, the viscosity and electrophoretic mobility of retorite clay slurry are further improved, and the rectorite particles exfoliate, splitting into rectorite microsheets with a large surface area. The rectorite microsheets with an irregular fold morphology form a mechanical locking structure, and bauxite clinkers are wrapped in a rectorite microsheet network construction, helping resist external forces. The cold crushing strength (CCS) of the brick combined with rectorite clay is higher than in kaolin clay after heat treatment at 110 °C or 750 °C. And the CCS (110 °C drying) is further improved after dry/wet grinding of rectorite clay slurry, reaching 31.1 and 35.0 MPa, respectively. The refractoriness under load test showed that rectorite clay bonded bricks performed low strength at temperature above 1200 °C because of high K2O and Na2O impurities in rectorite clay raw material. So the wet ground rectorite clay slurry bonded high alumina bricks have a broad application prospect at temperature below 1200 °C.