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[PE1-067] Investigation of the basic oxygen furnace slag as fine aggregate in concrete materials
Keywords:basic oxygen furnace slag, coal ash, concrete materials
The Basic Oxygen Furnace (BOF) slag is the by-product of steelmaking. There are low abrasion, low sodium sulfate bonds, and high hardness in BOFs graded aggregates. Their bearing capacity is better than that of natural graded materials. But it has now encountered great difficulties in reuse and utilization. The reasons are mainly the existence of f-CaO/MgO in BOF slag. Due to the existence of f-CaO in slag, the volume of slag expands during hydration, limiting the uses of BOF slag. To prevent BOF slag from expansion is the key for slag utilization.
This paper discussed the feasibility of BOF slag used as fine aggregate in concrete materials. Try to solve the expansion problem of BOF slag, we add coal ash as an additive material to explore the optimize ratio of the BOF slag and coal ash. The fine aggregates was replaced on the basis of weight proportion, with substituted amounts of 0%, 30%, 50% and 70%, respectively. The optimize proportions is coal ash (20%) and BOF (80%), i.e. BOF-to-coal ash ratio=4:1. For normal weight concrete, the designed strength were 210 kgf/cm2 (W/C=0.6), 280 kgf/cm2 (W/C=0.5) and 350 kgf/cm2 (W/C=0.4) respectively. For mechanical properties, with the same age (28 days) and the replacement of BOF mixture (0%), the compressive strength is 349.6 kgf/cm2 (W/C=0.4); 295.9 kgf/cm2 for W/C=0.5; 216.63 kgf/cm2 for W/C= 0.6. For the replacement of BOF mixture (70%), the compressive strength is 483.58 kgf/cm2 (W/C=0.4); 484.1 kgf/cm2 for W/C=0.5; 417.7 kgf/cm2 for W/C= 0.6. For alkali reactivity of aggregates (ASTM C1260), the measurement was ended on day 28 and the shrinkage is -0.050 % ~ 0.177 % in various proportions. With the increase of the ratio of BOF mixture in place of fine aggregates as well as the increase of the maintenance temperature, the abundant alkali made its concentration within the concrete rise and accelerated preliminary reaction, resulting in larger expansion. The results show that the coal ash can effectively inhibit the expansion of BOF slag.
This paper discussed the feasibility of BOF slag used as fine aggregate in concrete materials. Try to solve the expansion problem of BOF slag, we add coal ash as an additive material to explore the optimize ratio of the BOF slag and coal ash. The fine aggregates was replaced on the basis of weight proportion, with substituted amounts of 0%, 30%, 50% and 70%, respectively. The optimize proportions is coal ash (20%) and BOF (80%), i.e. BOF-to-coal ash ratio=4:1. For normal weight concrete, the designed strength were 210 kgf/cm2 (W/C=0.6), 280 kgf/cm2 (W/C=0.5) and 350 kgf/cm2 (W/C=0.4) respectively. For mechanical properties, with the same age (28 days) and the replacement of BOF mixture (0%), the compressive strength is 349.6 kgf/cm2 (W/C=0.4); 295.9 kgf/cm2 for W/C=0.5; 216.63 kgf/cm2 for W/C= 0.6. For the replacement of BOF mixture (70%), the compressive strength is 483.58 kgf/cm2 (W/C=0.4); 484.1 kgf/cm2 for W/C=0.5; 417.7 kgf/cm2 for W/C= 0.6. For alkali reactivity of aggregates (ASTM C1260), the measurement was ended on day 28 and the shrinkage is -0.050 % ~ 0.177 % in various proportions. With the increase of the ratio of BOF mixture in place of fine aggregates as well as the increase of the maintenance temperature, the abundant alkali made its concentration within the concrete rise and accelerated preliminary reaction, resulting in larger expansion. The results show that the coal ash can effectively inhibit the expansion of BOF slag.
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