Preparation And Hydration Characteristics Of Steel Slag And Blast Furnace Slag-based Foam Concrete

Based on resource utilization of industrial waste,such as steel slag,mineral slag and de-sulfuration gypsum,and the low-cost preparation of noise reduction materials,this thesis focuses on the foamed steel slag concrete prepared on the basis of steel slag,mineral slag and de-sulfuration gypsum.The mainly issues include the optimization of grinding process,basic performance and sound absorption property,thermal conductivity and hydration mechanisms.Magnetic de-ironing and grinding processing not only can increase the grind-ability and grinding efficiency,but also can reduce the energy consumption.And it possible to achieve large-scale industrial production of super-fine steel slag powder.Research results of the optimization of the basic performance suggest that the optimal ratio of contents in foamed steel slag concrete are as follows:steel slag is 28 wt.%,mineral slag is 60 wt.%,de-sulfuration gypsum is 12 wt.%,water-binder ratio is 0.45,water reducing agent is 3 ‰(in all cementitious materials)and fiber is 3 wt.%(in all cementitious materials).The density of the sample is 671kg/m3,while the compressive strength can reach 6.29 MPa after 28 days maintenance at the condition of 70℃,which satisfy the strength requirements of the JG/T266-2011 standard for foam concrete A07 foam concrete.The results on the optimization of sound absorption property indicate that foamed steel slag concrete can get good sound absorption property at middle-low frequency when aluminum powder content is added by 2 ‰.In the pilot project,the noise reduction capability of the foamed steel slag concrete could be comparable with widely-used fiber micro-perforated plate,but the cost is only 1/4 of the fiber micro-perforated plate.In this regarde,it can accomplish the aim of low-cost noise reduction in substation project.Thermal conductivity study of foamed steel slag concrete show that energy propagation mainly occur in the foamed concrete matrix.The increasing number of stomata extends the energy propagation path,whilst reduces solid thermal conductivitywhich plays a thermal insulation effect.Thermal conductivity simulation results suggest that CT scanning stomatal reconstruction model is much better in reflecting the authenticity of foamed steel slag concrete when compared to stomatal stochastic distribution model.Based on the investigation of hydration process of cementitious materials with steel-slag,mineral slag and de-sulfuration gypsum system by XRD,SEM,XPS and NMR methods,the mineral slag hydration is dominant in the early stage,which result in the formation of ettringite and C-S-H gel promote the strength increasing in the early stage.In the middle-late stage,divalent alkali metal ion is formed by steel slag hydration which further promote rapid and continuous formation of ettringite and C-S-H gel.Sheet C-S-H gels in the early stage also turned into more dense spherical C-S-H gels in the late stage.Interspersed structure of ettringite and C-S-H gel density can improve the strength of foamed steel slag concrete more effectively in the middle-late stage.