| The coarse steel slag and cement raw materials were mixed to calcine in this study, which focus on mineral category and morphology of steel slag and interactions between coarse steel slag and cement raw materials after calcined in different temperature by using of XRD, SEM, heat of hydration analysis and so on. The result showed that the replacement of cement raw materials by coarse steel slag decreased the emission of CO2, the decomposition temperature of Ca CO3 also declined, which reduced the energy consumption and emissions in the process of calcination. As the addition of steel slag, the clinker calcining eutectic temperature droped, which is conducive to the absorption of free calcium oxide in mineral, its content also decreased significantly, also the burnability of clinker improved. After calcination, the type and amount of mineral in steel slag changed, the amount of free oxide decreased,the content of mineral with iron and aluminum phase increased. The XRD pattern shows that the position of characteristic peak of RO phase changed after calcined at high temperature, which indicated that the majority of chemical composition of RO phase transformed from Fe O to Mg O, The higher the temperature, the deeper the transformation. According to the EMS morphology analysis of the interface between large sized slag particle and raw material and XRD analysis, reactions can be inferred in the transitional region between various sized slag and raw materials particles under different temperatures. Flakes and fluffy particles with Fe, Al and Ca as its primary elements appeared. Along with the XRE analysis, it can be concluded that the mineralogical phases in the transition regions could be one or more of C2 AF, and C2 F or CA,The chemical reactions in transition area were based on the Ca from raw material particles and Fe, Al from slag particles. As the temperature went up, the contents of Fe and Al phases in this region increased significantly. which implied more slag involved in reactions.With the addition of five to fifteen percent of coarse steel slag, the grindability of clinker pefermace well, the grindability dcreased largely, while the addition of steel slag exceeded fifteen percent. compared with reference sample, the heat flow and heat of clinker with steel slag decreased, the early strength declined to a certain degree,the late strength increased apparently, after calcined at 1450℃, compared with reference sample the 28 d compressive strength of clinker with addition of 15% steel slag only lose 1.22 MPa. The decline of early strength is mainly due to the increase of iron phase which brought by steel slag, led to the growth of C4 AF content and declineof C3 A content. after the early hydration, pore number of cement paste increased, with the prolongation of ages, harmful pores were filled, this also be one of important factors that the late strength with steel slag growed rapidly.The conclusion mentioned above is applied to the 2500t/d new dry-process kiln of Southern Cement Company Limited in Shaofeng, Hunan Province. The experiment results showed that the mixing of large sized slag with raw materials lowered the C3 S and C3 A contents, but increased the contents of C2 S and C4 AF in cement clinker.Therefore, the heat release rate and released heat of hydration of cement are both decreased, which showed great advantages in the production of low-heat cement and road cement. Meanwhile the increase of C3 S and C3 A enhanced the sulfate corrosion resistance property of cement. Ten percent of replacement rate of raw materials with large grained slag over was used to produce high quality clinker which has less free lime, compact structure, and distributed evenly. |
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