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Engineering the Microstructural Parameters of Erosion Resistant High Alumina Castables

In this sense, this work investigated the performance of high-alumina castable compositions containing: (i) different amounts of calcium aluminate cement (CAC) as binder, (ii) white or brown-fused alumina as coarse grains, (iii) distinct maximum particle size and distribution modulus of the formulations, and (iv) sodium borosilicate (0–5 mass-%) as a sintering additive, during erosion measurements. Besides the determination of the eroded volume of samples fired at distinct temperatures (600–1200 °C), apparent porosity
and hot modulus of rupture of the designed formulations were also analysed. The obtained results indicated that the most promising evaluated composition comprised 10 mass-% of CAC as, specimens with lower cement amounts resulted in high eroded volume or even full erosion. No significant changes in the measured eroded volume could be detected for the refractory formulations containing white or brown-fused alumina aggregates and coarse grains with different particle size, as the matrix fraction (fine
components) is the main area of the castables to be worn due to the SiC particles’ impact. The addition of sodium borosilicate to the castables helped to improve their erosion resistance (due to the generation of a boron-rich liquid phase and its further interaction with the other available oxides), when pre-firing the samples at intermediate temperatures (800 °C, 1000 °C or 1200 °C for 5 h).


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