Type high alumina Items B1 B2 B3 B4 B5 B6 B7 physical properties Permanent linear change d 900 1000 1100 1200 1300 1400  1500 Bulk density 0.7 0.7 0.75 0.8 0.8 0.9 1 Cold crushing strength  e 2.4 2.4 2.4 2.4 2.4 3 3 Thermal conductivity   d 0.2 0.21 0.23 0.26 0.27 0.31 0.36