1. 1. REFRACTORIES Refractory Any material that resists heat is called Refractory. Refractory Concrete can withstand temperature from 300 o C to 1300 o C. 1. Refractories 1

2. Refractory Linings Bricks and rocks that are hard to melt and therefore used for lining furnaces are called refractory linings. Service temperature limits are controlled more often by the aggregate than by the cement. High Alumina Cement (HAC) can withstand 1200 o C (but concrete made from it with silica gravel and sand should not be used at temperatures above 300 o C), limestone can withstand temperature of 500 o C, blast-furnace slag (dense or foamed) brick or calcined diatomite (B), can stand a temperture of 800 o C; 1. Refractories 2

3. Some igneous rocks, including basalt, dolomite and pumice, as well as expanded clay aggregate, will resist at least 1000 o C, dead-burned magnesite can resist temperture of 1400 o C; bauxite can resist a temperture of 1500 o C, chromite can resist a temperature of 1600 o C. A Refractory lining material low in silica content, used for metallurgical furnace linings. It contains metal oxides like lime (CaO), magnesia (MgO), or calcined dolomite, a mixture of two. 1. Refractories 3

4. Bauxite Is the most important ore of Aluminium, Al 2 O 3.2H 2 O, named after Les Baux in Provence. It does not fuse below 1600 o C. It is used as a refractory, and as the raw material for bridge decks after 1945. Calcium Aluminate The refractory part of H.A.C. consists of various calcium aluminates, some of them being even more refractory than monocalcium aluminate, which is white and melts at 1608 o C. 1. Refractories 4

5. Carborundum A trade name for silicon carbide, a refractory and abrasive which is harder than quartz. It can be used at temperatures up to 2500 o C. Silica Bricks Refractory brick which contains over 90% silica, and being bonded with lime will stand temperatures from 1650 to 1750 o C before it softens. Zirconia (ZiO 2 ) Zirconium oxide, a refractory which can be used at very high temperatures. 1. Refractories 5

6. refractories 1. Refractories 6