Abstract
Four extremely intimate mixtures were prepared of c. p. calcium carbonate, and silica. and magnesiumhydroxide. They were composed of 100 parts of 3CaO+SiO2 and 0, 2, 4, and 6 parts of MgO when ignited thoroughly. 1/3 mol of SiO2 was added to each mol of MgO in order to leave a part of the latter in free state, if any chemical reaction occur between the two oxides. The mixtureswere heated at 1500°C for 90 minutes once, twice, thrice, and four times, the heated products having been pulverized very fine each time.
Sixteen samples thus prepared were examined for the chemical composition, microstructure, and X-ray diffraction to find the influence of magnesia upon the formation of tricalcium silicate. Meanwhile, an investigation was carried out for the determination of free magnesia in the samples.
The results of the chemical analyses indicate that the formation of tricalcium silicate is accelerated by the presence of magnesia, that the effect of magnesia increases as its amount increases, and also that the repitition of the heating and pulverization favors the formation of the silicate. The results were verified by microscopic examinations and X-ray analyses.
Exactly speaking, the attempt of determining free magnesia by the combination of the Rathke's method of determining free lime and the method of N. A. Tananaeff and L. M. Kuehlberg for the determination of free lime and magnesia was not very successful. However the combined method seems to be promising.
