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Journal of the European Ceramic Society, Volume 34, Issue 5, May 2014, Pages 1365-1373.
Cem Gogtas, Hugo F. Lopez, Konstantin Sobolev.
Department of Materials Science and Engineering, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, WI 53211, United States and
Department of Civil Engineering and Mechanics, University of Wisconsin-Milwaukee, 3200 North Cramer Street, Milwaukee, WI 53211, United States.
Abstract
In this work, Al2O3 self-flowing castables (SFCs) were produced based on various cement contents. The SFCs were sintered at 1273 K, 1573 K and 1773 K and the exhibited properties were experimentally determined. Among the properties determined in this work are bulk density (BD), apparent porosity (AP), water absorption (WA), cold crushing strength (CCS), modulus of rupture (MOR) and fracture toughness (KIC). It is found that additions of 5% cement lead to SFCs with maximum MOR and KIC values after firing at 1773 K. Firing at 1573 K leads to a reduction in both, MOR and KIC. In SFC containing 3% cement, maximumKIC values of 3.53 MPa m1/2 were achieved after firing at 1573 K. In the low cement SFCs (1 wt%) after firing at 1773 K the exhibited KIC values were below those obtained in either the SFC-3 or SFC-5, but they were significantly high (3.43 MPa m1/2).
Additional Information.
In this work, low cement self flowing castables (SFCs) were processed. A water addition of 5.5 % was found to be enough to achieve full self flow properties. It was found that the self flow values decreased as the volume fraction of hydratable alumina was increased. Drying at 383 K, produced a fully corundum matrix structure in all the SFCs. The formation of anorthite was observed in SFC-5 (5% cement) and SFC-3 (3% cement) at 1273 K and 1573 K, respectively. In contrast, cristobalite was found to be present in SFC-1 (1% cement) at 1573 K. At 1773 K, SFCs having 1 and 3 % cement content developed relatively large amounts of mullite as evidenced by X-ray diffraction.
The cold crushing strength values were found to reach a maximum at 1573 K in the SFC-3 and SFC-1 castables and at 1273 K for the SFC-5 ones. In addition, in the SFC-3 and SFC-1 castables, KIC (fracture toughness) and MOR (modulus of rupture) values were found to consistently increase with the firing temperatures as a result of the development of ceramic bonding. In contrast, a slight drop in KIC and MOR values was observed in the SFC-5 at 1573 K, probably due to the formation of anorthite. Yet, the exhibited KIC in the SFC-5greatlyimproved after firing at 1773 K. The highest values of BD corresponded to the lowest values of AP and they were attained after firing at 1773 K in all of the castables.
