Effect of Composition and Temperature on Structure and Early Hydration Activity of Modified Steel Slag
The process that steel slag from electric arc furnace(EAFSS) and fly ash(FA) were incorporated into ordenary oxygen furnace steel slag(BOFSS) to reheat and modify its mineralogical composition and structure at high temperature was simulated in laboratory. The effect of composition and structure of modified BOFSS on its hydration activity was investigated. The mineralogical composition, microstructure and hydration activity of both BOFSS and modified steel slag(MSS) were investigated with X-ray diffraction (XRD), optical microscopy, determination of compressive strength and isothermal calorimeter. The results show that after modification, the amount of silicate minerals in MSS is decreased with increasing use level of FA, whereas the amount of silicate minerals is increased with increasing use level of EAFSS. As a result, the crystal size of alite in MSS becomes bigger with low alkalinity, however, amount of alite in MSS with high alkalinity is increased, and morphology of alite in MSS is regular with much less free CaO. The cumulative hydration heat for sample GB40-1350 is greater than that for BOFSS by 1. 9 times at 3 days, and the compressive strength of cement paste incorporating 30%(by mass) of ground sample GB40-1350 to replace cement reaches 99. 9% of that for pure cement pastes at 28 days.
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