A large number of clinkers with wider varying composition in two systems, i. e. “A” SiO
2-Al
2O
3-Fe
2O
3-CaO, and “B” SiO
2-Al
2O
3-Fe
2O
3-CaO-MgO was prepared synthetically from pure chemicals in an electric furnace under different heating temperature and duration, and the production was carefully investigated by microscopical methods, a result of which is summarised as below:
(I) The formation of Alit in the clinkers in system “A” is very poor compared with those in system “B”, the both systems having been prepared under identical conditions. In the latter case a very small amount, for example, 0.56% MgO has a great influence on the structure and gives a wonderful effect on the crystallization of the above-mentioned clinker mineral. This fact was ascertained on the clinkers prepared in the same manner from pure chemicals except CaCO
3, instead of which natural limestone containing a small amount of MgO was used.
(II) The color of the clinkers thus prepared in both systems was examined in powdered form with Ostwald's Universal Photometer. All clinkers in system “A” have the value of v/w=1.2-1.4, Color No. =15th-16th, and yellow or yellowish brown color, while the clinkers in system “B” containing 0.5-6.5% MgO shows v/w=0.2-0.5, Color No. =12th-14th, and greyish green or dark green color. Many samples containing 0-0.5% MgO and also three samples in which MgO was replaced by 0.1-0.4% MnO
2 gave v/w=0.6-0.9, Color No. =13th-14th and greyish brown color.
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