Governing role of particle size in expansion of cement composites incorporating basic oxygen furnace slag

This is the authors' abstract. We don't add key points for this paper.

This study investigates the particle-size effect of basic oxygen furnace (BOF) slag on the expansion behavior of cement composites experimentally. The objective is to identify a practical particle-size range that ensures expansion stability while avoiding excessive grinding. BOF slag was classified into nine particle-size groups (45–4, 750 μ m ) and tested at incorporation ratios of 10% and 20%. The expansion behavior does not vary linearly with particle size. Coarse particles induce localized expansion and stress concentration, leading to cracking and fracture, whereas finer particles promote more uniform hydration and distributed expansive stresses. All fractions of 600 μ m and above fractured, and the 600 μ m fraction exhibited the most severe damage with a large expansion and the shortest time to fracture, indicating a critical particle size for expansion-induced deterioration. Controlling BOF slag particle size below 300 μ m effectively mitigated expansion-induced cracking while improving mechanical performance. These findings demonstrate that particle-size control provides a practical and energy-efficient approach to stable use of BOF slag in construction materials.