Basic refractories direct bonded

The resistance against thermal spalling of fireclay and high alumina brick is indicated in Table 5. No standard test has been adopted for basic brick. Refractories composed of 100% magnesia exhibit poor thermal shock resistance, which is improved by addition of chrome ore. So-called direct bonded basic brick, composed of magnesia and chrome additions, exhibits good thermal shock resistance. 

Phosphate Bond. Cold-setting bonds for refractories can be formed by reactions between oxides and phosphoric acid, phosphate-phosphoric acid reactions or the direct use of liquid phosphate bonds. The bond is due to the formation of an acid phosphate, with weakly basic or amphoteric oxides. 

---