In continuing the previous studies (Reports 1-6), in the present paper were reported the results of fundmental studies on the factors relating to the important physical properties of the special alumina cements obtained from high aluminous residue of potassium sulphate extraction of alunite ores.
Various compounds, which can be surmised to be produced and contained in the clinker of the present special alumina cements from alunite, of calcium aluminates (mCaO⋅nAl
2O
3), calcium silicates (mCaO⋅nSiO
2), calcium alumino-silicates (1CaO⋅mAl
2O
3⋅nSiO
2), calcium ferrites (mCaO⋅nFe
2O
3), calcium alumino-ferrites (1CaO⋅mAl
2O
3⋅nFe
2O
3), ferrous silicates (mFeO⋅nSiO
2), ferrous aluminates (mFeO⋅nSiO
2), calcium magnesio-silicates (1CaO⋅mMgO⋅nSiO
2), etc., were fully discussed and compared with those from other samples of common alumina cements, by various studying methods of microscope, X-ray analysis, separation of fine crystal powder by heavy liquide, etc.
Among these results, the large amount contamination of 2CaO⋅Fe
2O
3 in the heavy specific gravity part (above 3.33) has the most inferior effect on the hardened strength, and the exsistences of 3CaO⋅Al
2O
3 and various alumino-silicates mAl
2O
3⋅nSiO
2 (sillimanite Al
2O
3⋅SiO
2, mullite 3Al
2O
3⋅2SiO
2, etc.) are of most ambiguous points, which must be studied in the future studying.
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