Particle Distribution Design in a Self-Flow Alumina Refractory Castable without Cement

Abstract:

A self-flow refractory castable (SFRC) without cement requires a matrix of fine particles and a broad size distribution of coarse particles (aggregate). The matrix ensures the rheological behaviour and performs the binding role of the absent refractory cement. The presence of the aggregate coarse particles hinders the flowability index (FI), but improves the castable mechanical strength and reduces firing shrinkage. A new methodology of SFRC particle distribution design was developed, using response surface statistical modelling and commercial alumina powders (reactive and tabular). First, the composition of the fine matrix was optimised, seeking minimum water content and maximum IF. To this matrix, various aggregate distributions, combining six tabular alumina size fractions and with different Andreasen distribution modulus, q, between 0.18 to 0.28, were added, to identify the composition with maximum FI. The results obtained show that a minimum specific surface area (SSA) of 2.22m2/g is necessary to reach the self-flow turning point, after which the largest FI requires the maximisation of the aggregate maximum paste thickness (MPT), corresponding to a distribution with q=0.22. The optimised castable composition presents high mechanical strength (>60MPa) and low shrinkage.

• Periodical: Advances in Science and Technology (Volume 45)
• Pages: 2260-2265
• DOI: https://doi.org/10.4028/www.scientific.net/AST.45.2260
• Online since: October 2006
• Authors: Abílio P. Silva, Ana M. Segadães, Tessaleno C. Devezas
• Keywords: Aggregate Optimisation, Particle Size Distribution (PSD), Self-Flow Refractories

References

[1] I.R. Oliveira, A.R. Studart, R.G. Pileggi and V.C. Pandolfelli: Dispersão e Empacotamento de Partículas (Faz. Arte Edit., S. Paulo 2000) (Particle dispersion and packing, in Portuguese).

[2] A.R. Studart, W. Zhong and V.C. Pandolfelli, Am. Ceram. Soc. Bul. Vol. 78 (1999), p.65.

[3] A.P. Silva, A.M. Segadães and T.C. Devezas, Mater. Sci. Forum Vol. 514-516 (2006), p.604.

[4] S. L Correia, D. Hotza and A.M. Segadães, Ceram. Forum Int. Vol 82 (2005), p. E39.

[5] S. L Correia, D. Hotza and A.M. Segadães, J. Eur. Ceram. Soc. Vol 24 (2004), p.2813.

[6] A.P. Silva, A.M. Segadães and T.C. Devezas, Cerâmica Vol 50 (2004), p.345 (in Portuguese).

[7] R. Myers and D. Montgomery: Response Surface Methodology (J Wiley & Sons, NY 2002).

[8] J. Cornell: Experiments with Mixtures (J Wiley & Sons, NY 2002).

[9] A.P. Silva, A.M. Segadães and T.C. Devezas, Optimação da Distribuição Granulométrica da composição do Agregado Para um Betão Auto-Escoante Sem Cimento, Procedings of Engenharia'2005 (Covilhã, Portugal 2005), CD-Rom session 25-06, (Optimization of the aggregate particle size distribution for a no cement self-flow castable, in Portuguese).

[10] S.C. Carniglia and G.L. Barna: Handbook of Industrial Refractories Tecnhology (Noyes Pub., NY 1992).

[11] A.P. Silva, A.M. Segadães and T.C. Devezas, Relações entre Distribuição Granulométrica, Morfologia e Empacotamento de Partículas num Sistema Real: Alta-Alumina, Proceedings of 47 CBC (João Pessoa, Brazil 2003), p.150.