Particle-size dependent expansion of cement composites incorporating steel slag

This study investigates the expansion behavior of cement composites incorporating a steel slag through experiments and modeling depending on its particle sizes. Microstructural observations were conducted to analyze the expansion mechanisms of the steel slag. Different sizes of slag particles from sieve #4 to #325 were incorporated into cement composites at various contents to examine the expansion behavior. Experimental results showed that the threshold particle sizes for abrupt expansion at 90 °C were 2.36, 1.2, 0.6, and 0.6 mm when the slag contents were 10, 15, 20, and 30%, respectively. A homogenization model considering key parameters, including slag content, particle size, free CaO, and velocity of reaction front, captured the observed size-dependent expansion behavior successfully. The findings suggest that steel slag up to 0.3 mm can be safely used, significantly reducing grinding energy while keeping the stability. The results are limited to expansion behavior observed under the prescribed accelerated curing condition.