Magnesia and spinel refractory brick

An improved cement kiln refractory shape for lining cement kilns, said refractory shape comprising sintered magnesium oxide and MgO.Al.sub.2 O.sub.3 spinel, said refractory shape having high resistance to temperature changes and good pressure flexibility;

• said refractory shape consisting essentially of:
• between about 82 to about 90 percent by weight of magnesium oxide;
• between about 10 to about 18 percent by weight Al.sub.2 O.sub.3 ;
• and
• a content of up to about 3 percent by weight impurities;
• said impurities comprising CaO, Fe.sub.2 O.sub.3 and SiO.sub.2 ;
• said refractory shape being fired at a temperature of between about 1450.degree. C. and about 1600.degree. C.;
• said refractory shape when fired having a refractoriness under load of more than 1740.degree. C. and a change of dimension under compression at a load of 0.2 N/mm.sup.2 of about -3 to about -5 percent at 1400.degree. C. after 24 hours;
• said refractory shape being manufactured from the following starting materials:
• a magnesium oxide sinter;
• and
• an MgO.Al.sub.2 O.sub.3 spinel;
• wherein about 35 to about 42 percent by weight of said starting materials is magnesium oxide sinter having a grain size of less than about 0.09 mm;
• said starting magnesium oxide sinter having a CaO content between about 1.5 and about 3.5 percent by weight;
• said starting magnesium oxide sinter having a CaO/SiO.sub.2 ratio by weight of more than about 2.5.