Loading...
2 results
Search Results
Now showing 1 - 2 of 2
- Effect of particle size distribution and calcium aluminate cement on the rheological behaviour of all-alumina refractory castablesPublication . Silva, Abílio P.; Segadães, A M; Pinto, Deesy G.; Oliveira, Luiz A.; Devezas, TessalenoPrevious works based on statistical design of experiments (DoE) defined a model all-alumina self-flow refractory castable (SFRC) with optimized particle size distribution for simultaneous high flowability index (FI) and superior post-sintering performance. This work compares the SFRC rheological behaviour and setting time with those of alternative all-alumina castables with different Andreasen aggregate particle size distribution modulus, and of the equivalent castables containing calcium aluminate cement. The model castable showed Bingham behaviour with low yield stress, viscosity and thixotropy, guaranteeing easier casting and less wear in the casting and/or projection equipment. However, as the coarse particle fraction increases, the castable flow tends to be non-linear and changes from Bingham to Herschel–Bulkley. The cement containing castables quickly loose flowability despite the applied shear. This work confirmed previous conclusions based on FI measurements and demonstrates the adequacy of the use of FI values in the calculation of FI response surface by DoE.
- Castable systems designed with powders reclaimed from dismantled steel induction furnace refractory liningsPublication . Silva, Abílio P.; Segadães, A M; Lopes, Rogério A.Despite environmental pressures and intrinsic recycling potential, spent refractories waste is generally considered an economically unattractive waste stream. This work proposes an upgraded view of the debris recovered from dismantled spinel-bonded high-alumina linings of steel induction furnaces, demonstrating that it can be reused in the form of vibratable and self-flowing castable systems. The recovered material retains the microstructural distribution of in situ spinel formation without the corresponding disruptive expansion, mirroring the use of pre-formed spinel without the onus of a pre-firing. The mechanical performance after firing was found to be always best for the self-flowing system, which is also less affected by changes in added-water content. There is potential for large usages of cleaned waste (50–60 wt%), which helps reducing the supply risk for major refractory primary raw materials as well as landfilling costs.