Two kinds of ordinary portland cement clinker, widely different in MgO and SO_3 content, were reheated at 1550 °C for 20hrs. With the clinker rich in MgO and SO_3, alite increased while belite decreased in content after reheating The alite crystals in the initial clinker were overgrown with new precipitates showing definite zonal structures New crystallization centers were occasionally nucleated in the liquid to form thin platy hexagonal crystals. Supercooling formed dendritic belite crystals Reheating decreased the average C/S ratio of the interstitial phase. Those changes occur in conjunction with the process in which the interstitial liquid, variable in basicity in the initial clinker, is transformed to the liquid uniform and most acidic in composition. The process, controlled by the counter-diffusion of CaO and SiO_2 under small concentration gradient. is low in rate In normal clinker processing the clinkering reaction terminates before proceeding to that stage The presence of MgO and SO, in abundance lowers the viscosity of the liquid and accelerates the process. In this respect no appreciable texture change could be recognized for the clinker low in MgO and SO_3. With temperature rise the interstitial liquid increases in content assimilating C_2S and becomes richer in SiO_2. leading to higher solid C_3S/C_2S ratio in resultant clinker.
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