Magnesia-ammonium phosphate-bonded cordierite refractory castables: Phase evolution on heating and mechanical properties
A cordierite refractory castable was developed using the MgO-NH{sub 4}H{sub 2}PO{sub 4} reaction. This castable was made with cordierite-mullite aggregates from scrap refractory material and a cement paste based on magnesia, calcined alumina, silica fume, and ammonium dihydrogen phosphate, which forms cordierite (2MgO{center_dot}2Al{sub 2}O{sub 3}{center_dot}5SiO{sub 2}) during heating at high temperature. The mix with water was cast into steel molds; the cold setting occurs within 30 min. The set castables were thermally treated and the evolution of the phases was observed. Struvite (NH{sub 4}{center_dot}MgPO{sub 4}{center_dot}6H{sub 2}O) was identified at room temperature; between 110 and 750 deg. C, the present phosphates were amorphous to X-ray diffraction (XRD). At 1100 deg. C, magnesium orthophosphate (Mg{sub 3}(PO{sub 4}){sub 2}) and aluminum orthophosphate (AlPO{sub 4}) were present. At 1350 deg. C, the main crystalline phases were cordierite and mullite. Cold and hot flexural strength, thermal shock resistance, and physical properties were measured. The properties of magnesia-phosphate-bonded cordierite castables were compared with cordierite material obtained by conventional slip-casting method from aggregates, clay, talc, and calcined alumina.
- OSTI ID:
- 20658333
- Journal Information:
- Cement and Concrete Research, Vol. 34, Issue 1; Other Information: DOI: 10.1016/S0008-8846(03)00256-4; PII: S0008884603002564; Copyright (c) 2003 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM OXIDES
ALUMINIUM PHOSPHATES
AMMONIUM PHOSPHATES
CEMENTS
CERAMICS
CLAYS
FLEXURAL STRENGTH
HEATING
MAGNESIUM OXIDES
MAGNESIUM PHOSPHATES
MULLITE
REFRACTORIES
SCRAP
SILICA
SLIP CASTING
STEELS
TALC
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
X-RAY DIFFRACTION