Type high alumina Items B1 B2 B3 B4 B5 B6 B7 Physical properties Permanent linear change ín 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 & nbsp & nbsp; 2.4 2.4 2.4 2.4 2.4 3 3 Thermal conductivity & nbsp; & nbsp & nbsp; 0.2 0.21 0.23 0.26 0.27 0.31 0.36