Study On Preparation And Foaming Modification Of Medium-high Activity Reconstructed Steel Slag Powder

Steel slag is the by-product discharged from the iron and steel smelting process.Its main mineral phase composition is C₃S,C₂S,etc.,which are similar to Portland cement clinker components and can be used to replace part of the cement clinker for concrete preparing.However,it has plenty of low-hydration-activity mineral phases,as well as the high content of the hard and difficult-to-grind iron and RO phase,and the excessive f-Ca O and f-Mg O which may caused the problem of volume expansion and cracking in the cement concrete products made from it.These factors limit the large-scale utilization of steel slag in the field of building materials.Therefore,steel slag is modified in this article,the composition design and preparation technology of medium and high activity reconstructed steel slag powder are mainly studied,the influence laws of the composition and sintering process on the properties and microstructure of the reconstructed steel slag are proved,and the mechanism of the hydration activity of the reconstructed steel slag modified by the foaming agent is revealed.The main work and results are as follows:The high-temperature phase reconstruction of steel slag was carried out with lime and bauxite as tempering components,and the effect laws of quenching and tempering components and sintering temperature on the cementitious mineral phase and hydration activity of the reconstructed steel slag were investigated.Among them,he formation of mineral phases such as C₂S and C₄AF is the highest,the grain development is relatively perfect,its hydration activity can be increased to 90.4%,and the 28d compressive strength of composite mortar prepared by replacing 30 wt%P·O42.5 cement is 41.2 MPa,when the designed mix ratio of the reconstructed steel slag is 75%converter steel slag,21%lime and 4%bauxite,obtained by sintering at a high temperature of 1290°C for 90 min,and by prepared air-cooling and quenching.At the same time,the content of f-Ca O in the reconstructed steel slag is reduced2.03%,and the stability is qualified.The RO phase in the reconstructed steel slag is digested and the grindability is improved.The specific surface area after grinding is increased by 17.0%compared with the original steel slag,and the average particle size is reduced by 11.79μm.The influence law of high temperature foaming agent-SiC on the grindability of the reconstructed steel slag is proved.SiC undergoes oxidation-reduction reactions above 1000°C and releases CO₂,during the high-temperature reconstruction of converter steel slag,resulting in the presence of more pores in the reconstructed steel slag,thereby forming porous reconstructed steel slag with high porosity.The specific surface area and hydration activity of the porous reconstituted steel slag increase,as the content of SiC increases and is less than 1.6 wt%.But the pore structure of the porous reconstituted steel slag is destroyed,and the calcium to silicon ratio is significantly reduced,and the content of gelling minerals is reduced,when the content of SiC is higher than 1.6 wt%.Among them,the performance of porous reconstructed steel slag is the best,when the content of SiC is 1.6 wt%.Its porosity,specific surface area and activity index can reach 31.79%,424.4 m²/kg,and 91.3%and increased by10.31%,19.72%and 0.9%,compared with the reconstructed steel slag of undoped high temperature foaming agent SiC,respectivelyThe effect laws of composite foaming agent on the grindability of reconstructed steel slag are revealed.The grindability of porous reconstituted steel slag first increased and then decreased with the increase of the content of SiC-CaCO₃composite foaming agent.Among them,the porous reconstituted steel slag has the best grindability when the composite foaming agent content is 0.8 wt%.,its porosity and specific surface area are increased by 8.48%and 34.86%,and the average particle size decreased by 33.21%,respectively,compared with the reconstituted steel slag with the same grinding time.At the same time,the activity index of porous reconstituted steel slag modified with composite foaming agent can be increased to98.2%,and the compressive strength of composite cement mortar prepared by replacing 30 wt%P·O42.5 can reach 44.8 MPa.