Oxjt nhom:chjem 4-7% tp clk xm.
-khj nug luyen clkxm al2o3 t/d cao voj oxjt sat 3 tao ra cac khoag celit :celit1 (c3a) ,celit2 (c4AF).
-Al2o3 tag thj chu yeu C3A tag.
 +xm chua nhju khoag c3a dog ket nhanh toa nhju nhjt khj dog ran kem ben trog m/truog nc va mtruong xam thuc ,xm co cuog do thap.
 +mat khac do c3a dog vaj tro chat log khj nug luyen clkxm neu ham luog c3a lon thj do nhot of pa log cao,kho tao khoag c3s ,va can tro hoat dog of lo nug ,do do tao ra cac lop co la wa day va cac vong ano o jon nug(vug nug).
-Al2O3 jam THJ NGUOC LAJ NHA.