The use of heavy oil with much sulphur for burnning portland cement clinker is less expensive. SO
2 and SO
3 in the exaust gas is afraid to bring about the air pollution, however, these compounds will completely be caught by raw material of portland cement in suspension preheater which has recently been developed. Portland cement with much sulphur is interested in the character as expansive material.
In present paper, the authors prepared portland cement clinker fit for the two advantageous attempts and studied the properties. Initially, various amounts of gypsum, such as 2, 5, 10, 20, and 30%, are added to powdered commercial portland cement clinker as base material. The pelletized mixtures are burned at 1450°C, for 30 minutes in electric resistance furnace. Since a part of SO
3 leaves the clinker during the burnning, the SO
3 content in burned clinker is usually less than that given before the burnning. The fusion temperature of clinker go down with increasing the content of SO
3.
The polished section of over-burned clinker with much sulphur shows the formation of large-grown crystal of alite. The bending and compressive strength of mortar made from these powdered clinkers shows maximum values in the range of 3% to 6% of the content of SO
3. The values are larger than that of a commercial portland cement used for comparing with the present clinkers with SO
3. Only the clinkers with SO
3 content over 6% have expansive effect in the length change in water and in air with R. H. 53%.
Of clinkers made by burnning without fusion, the bending and compressive strength of clinkers with SO
3 content in the range of 3% to 6% is similar to that of clinkers burned at 1450°C. But, the clinkers with the SO
3 content over 6% burned under 1300°C, which have ill-grown alite crystal on account of incomplete burnning, are lacking in the development of strength.
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