Hydration heat evolution and kinetics of blended cement containing steel slag at different temperatures

• Hydration process of steel slag was similar to cement, but its activity was very low.
• Small amount of steel slag affected little the hydration process of cement.
• Elevated temperature obviously promoted the hydration of blended cement.
• Hydration kinetics varied with different steel slag content and in different stages.
• Apparent activation energy increased with an increase in steel slag content.

Hydration heat characteristics of blended cement containing up to 50% steel slag were studied at 25 °C, 45 °C and 60 °C by isothermal calorimeter. Kinetics equations were used to explore kinetics of blended cement. Kinetics parameters, n, K, and Ea, were calculated and analyzed. Results indicated that the activity of steel slag was very low. Steel slag accelerated the hydration of aluminates but decelerated the hydration of silicates in cement clinker. Small amount of steel slag affected little the hydration process of cement. Elevated temperature obviously promoted the hydration of blended cement. The hydration of blended cement containing no more than 35% steel slag was controlled by nucleation of hydrates in acceleration period and by diffusion of ions in decay period. The hydration of blended cement containing 50% steel slag was mostly dominated by phase boundary reaction, then directly by diffusion. Ea increased with increasing steel slag content.