Influence of classified steel slag with particle sizes smaller than 20 μm on the properties of cement and concrete

• Fine steel slag (FSS) with particle sizes smaller than 20 μm was prepared.
• FSS shows good cementitious properties.
• The activity of FSS is a little lower than that of cement.
• The 20% FSS replacement has little negative effect on the properties of concrete.

In this study, steel slag was classified into two fractions by an air classifier: fine steel slag (FSS) with particle sizes smaller than 20 μm and coarse steel slag (CSS) with particle sizes larger than 20 μm. The hydration properties of FSS and its effect on the properties of cement and concrete were investigated. The results show that FSS possesses relatively good cementitious properties. Its activity is a little lower than that of Portland cement. Additionally, its hydration degree is slightly lower and its hydration products are relatively fewer compared with cement. FSS has nearly no influence on the porosity of paste and the strength of mortar when its replacement ratio is not more than 20%. The effect of FSS on the strength and drying shrinkage of normal concrete is negligible when its replacement ratio is not more than 20%. FSS affects the chloride permeability of normal concrete very little when its replacement ratio is not more than 30%. Adding FSS in high-strength concrete can decrease its autogenous shrinkage.

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