| Steel slag was the waste generated in the steelmaking process.The steel slag presented low activity,poor grindability,poor volume stability and other issues,which leading to more difficulty in achieving large-scale utilization.Large amount of steel slag not only occupied large areas of land but also caused damage to the surrounding environment.Concrete filled steel tube was a composite material formed in a pipe filled with concrete,with good performance of high capacity,resistance to deformation.But the void phenomenon caused by the large shrinkage of the core concrete had a bad effect on the bearing capacity of steel concrete.If the use of steel slag as cementitious material and fine aggregate to prepare steel concrete was feasible,the expansion components of steel slag could compensate the shrinkage of concrete.What's more,the advantage of the steel pipe's enclosed absolutely wet environment and its ferrule binding effect could avoid the occurrence of concrete damage from stability issue.Relying on the National Key Basic Research and Development Program?973 Program?"harsh environment long concrete materials and structures lifetime of basic research"first task"long-life micro-concrete structural material is formed under harsh environments and regulation"?2015CB655101?,carried out the research on the utilization of steel slag and granulated blast furnace slag as a cementitious material,steel slag sand as fine aggregate to prepare stimulate self-compacting expansive steel concrete,and achieved the following innovations achievements.Firstly,the 1.18-4.75mm aged for 1 year steel slag's pulverization rate was less than 6%under 205?,2.2MPa steam pressure.Its pulverization rate was less than 1%at 80?steam cured for 7d and the crushing value of the steel slag was less than 20%.It could be used as fine aggregate to prepare steel concrete.Secondly,the alkali-activator and the high-efficiency,plasticity-maintaining viscosity-reducing,low air entrained superplasticizer for the steel tube confined concrete cementitious systems composed by steel slag powder and GBFS?granulated blast-furnace slag?has been developed.The problem that alkali-activated steel slag powder and GBFS concrete with high viscosity,poor liquidity,and low plasticity retention has been effectively solved.The composition of this kind admixture was ultra-dispersed efficient plasticity-maintaining polycarboxylic acid:monopotassium phosphate:sodium gluconate:defoamer=30:1:1:0.018.The hydration and hardening mechanisms of the alkali-activated steel slag and slag powder cementitious paste and the interface between steel slag sand and it have been studied by the test methods such as hydration heat flow,NMR,XRD,SEM-EDS.Thirdly,the design and preparation methods of alkali-activated,self-compacting,expansive concrete composed with the cementitious materials such as steel slag powder and GBFS powder and the aggregate made by steel slag sand have been presented.The concrete,which using steel slag powder and GBFS powder as cementitious materials,steel slag sand as fine aggregate and mixed with the alkali-activator,which has been developed by the author,the superplasticizer and the expansion agent?comprised of CaO,C4A3 S?has been prepared.The workability was admirable?initial slump?250mm,initial slump flow?600mm,T500?15s,2h slump?230mm,2h slump flow?450mm,air content?2%?.The volume of the prepared C30C50 concrete turned basically stable after 28 days and the free swelling ratio reached 30×10-660×10-6.The 28d elastic modulus of self-compacting expansive steel tube confined concrete was 33.2GPa and the 60d creep coefficient?loaded after14d initial curing?was 1.2.The 60d creep coefficient of steel concrete composite structure was 0.7,and the ferrule coefficient was 1.09.The ultimate bearing capacity of short column wass greater than the sum of that of steel tube and concrete,and the ultimate bearing capacity of the strain was between that of steel tube and concrete.The results of this study could provide technical support for large-scale,high value-added use of steel slag and ease the situation of river-sand resource constraint caused by large-scale infrastructure construction.The application prospect of the achievements was broad. |
PDF Full Text Request