Hydration of Secar 71 aluminous cement in presence of granulated blast furnace slag

The hydration behaviour of a 1:1 mixture (by mass) of ‘Secar 71’ refractory aluminous cement and ground granulated blast furnace slag has been studied over a range of temperature using conduction calorimetry, x-ray diffraction and thermal analysis techniques. The initial hydration of the cement produces CAH 10 or C 2AH 8; at higher temperatures this is followed by limited conversion to C 3AH 6 and reaction with the slag producing gehlenite hydrate. The start strength of the cement plus slag mixture is considerably lower than that of the cement itself of ambient temperatures but when cured under water the strengths of the two materials become comparable after six months. When kept in hot water over a long period of time, the 1:1 cement plus slag mixture has not shown any reduction in strength. A possible explanation for this phenomenon is offered.