Bonding of cement clinker onto doloma-based refractories

Adherence ability of cement clinker on doloma refractories was investigated using a specially designed sandwich test conducted at 1550 degrees C for 30 min, under a load of 5.3 kPa. Fractional factorial experiments determined that silica ratio, particle size, and alumina ratio of raw meal had significant effects on the reactions between the clinker and the refractory. Silica ratio was found to be the most prominent factor influencing the adherence strength of the clinker on the surface of doloma bricks. Doloma refractory, having an excess of free lime, reacts with clinker to form additional C3S at the interface, which is greatly beneficial to adherence strength. The interface of doloma/clinker with low silica ratio is covered with a continuous MgO-enriched layer, which is formed from the CaO reacting with the raw meal in presence of a large amount of liquid phase generated in the clinker. This layer reduced the adherence strength of clinker on doloma. With high silica-ratio raw meal, clinker and doloma form a C3S-rich layer at the interface, improving strongly the adherence strength of clinker on the brick.