| High titanium slag(TS)is a kind of solid waste discharged from pig iron smelting usingvanadium titanium magnetite.With the development of steel industry,the discharge and storage content of TS has become increasingly serious which causes damage to the ecological envioronment.TS can be a high-quality alternative aggregate for its properties of stable,wear-resistant,high strength and has micro-volcanic activity.So far,however,TS is rarely used as the aggregate of high-strength and high-performance concrete.The microstructure and properties of the high performance concrete containing TS were lack of systemic research.And the interaction mechanism between TS and cement paste was still unclear.Therefore,in this research,TS was used as aggregate in high performance concrete aggregate to instead of natural aggregate.The properties,microstructure and the paste-aggregate interfacial interaction mechanism of the high performance concrete were studied,which was expected to improve the comprehensive utilization rate of high-titanium slag and provide a theoretical basis for the application of TS in high performance concrete.The proportion design method that suitable for the high performance concrete with porous aggregate was established according to the porous characteristics of TS particle.Two types of high performance concrete including high titanium slag reactive powder concrete(TSRPC)and high titanium slag high-strength and high-performance concrete(TSHPC)were prepared by using this method.The mechanical properties,hydration characteristics,autogenous shrinkage and durability of TSRPC and TSHPC were systemic researched.The focus was on exploring the microstructure of paste-aggregate interface of the high performance,revealing the mechanism of interaction between TS and cement paste.Finally,the environmental,economic and social benefit of TSRPC and TSHPC were comprehensively evaluated.It was found that while controlling the cement content less than 500 kg/m~3,the C120 to C180grades TSRPC and C80 grade TSHPC were prepared with more than 70%of solid waste utilization rate,which effectively improved the comprehensive ulitization rate of TS.The mechanical properties and durability of TSRPC and TSHPC were better than those of QSRPC and QSHPC.When reaching the same strength grade,TSRPC needed less content of steel fiber and low curing temperature than QSRPC,which is closely related to the particle structure,chemical composition of TS and the interaction mechanism of TS and cement paste.The internal curing effect of TS could effectively reduce the autogenous shrinkage of TSRPC after curing for 28 d,and the reduction rate was up to 6.47%.However,due to the low water absorption and insufficient water release of TS,the moisture of cement paste was hard to be maintained at later stage.The proper content of retarder could form a synergistic effect with TS to keep the internal humidity of TSRPC above 90%after hydration for 10 d.There were physical and chemical interactions between TS and cement paste.On the one hand,TS was rough and porous.At the early age,cement paste entered into the pore of TS particle and adhered onto the pore wall improving the bonding force of paste-aggregate interface by mechanically interlocking and increasing the contact area.At the same time,the dynamic balance of moisture between TS aggregate and cement paste was achieved through“water exchange”in concrete,thus avoided the directional growth of large-size portlandite crystals in ITZ(the interfacial transition region).On the other hand,the amorphous phase on the surface of TS reacted with cement paste forming C-S-H and its derivatives to fill into the interface gap,so as to improve the interface compactness and further enhanced the mechanical properties and durability of TSRPC and TSHPC.Compared with QSRPC and QSHPC,TSRPC and TSHPC had better comprehensive benefit.The production of 1 m~3TSRPC and 1 m~3 TSHPC reduced the environmental cost by 78.68 yuan and 22.49 yuan than QSRPC and QSHPC,respectively. |
PDF Full Text Request