| Ferronickel slag is by-product produced in the process of smelting ferronichel alloy,the amount of ferronickel emitted takes about 80%?90%of the raw material,and China's annual emissions over 30 tons,which has become the fourth smelting industrial waste residue just behind the slag,steel slag,red mud.Ferronickel slag adopt water quenching treatment,the mineral structure of it mainly as glassy,which possess components and activity of using as auxiliary cementitious materials,and has volcano activity.Ferronickel slag used as admixture is not only an effective way of ferronickel slag dispose,but also beneficial to energy saving and emission reduction for the cement industry.Ferronickel smelting technology is mainly divided into electric furnace and blast furnace smelting,the two kinds of smelting technology have great differences in raw materials and smelting process,resulting in chemical composition and basic properties of slag also have great differences,so the ferronickel slag can be divided into electric furnace ferronickel slag and blast furnace ferronickel slag.This paper mainly take blast furnace ferronickel slag powder(BFFN)as the research object,study the hydration characteristics on cement concrete and the influence on the performance of composite cementitious material hydration hardening paste,the main research contents and conclusions are as follows:(1)BFFN good grindability,in terms of chemical composition of blast furnace ferronickel slag powder,the content of MgO and SiO2 is high,but CaO is low,in terms of the mineral composition,the powder mainly contain spinel crystal,and XRD diffraction peak was significantly wider,which indicating that content of vitreous substance is high.(2)The early flexural and compressive strength cement-BFFN composite cementitious materiale is lower than that of cement,but the strength increased significantly with the increase of age.Low specific surface area of composite cement early strength is low,but the growth of late strength is significant.Improving the specific surface area of BFFN is beneficial to improve the early strength,but not conducive to the growth of late strength.(3)Compared with cement,the mix of BFFN leads to the decrease of exothermic rate and delay the occurrence point-in-time of hydration exothermic peak.In cement-BFFN complex binder,the reaction degree of BFFN and the content of chemical bonding water decrease with the increase of the increase of the ratio of BFFN.The mole ratio of Ca to Si of formed silicate calcium hydrate in cement-BFFN complex binder lower than cenment,and the Ca/Si decrease with the increase of hydration time.In the hydration process,the A1 contained in BFFN will form calcium silicoaluminate hydrate(C-A-S-H)gel by replacing Si of silicate calcium hydrate(C-S-H)gel.(4)The BFFN and superplasticizer has good adaptability,which used as mineral admixture will not produce negative affect on the working performance of concrete;when the content is 30%,the BFFN concrete has excellent mechanical properties.The chloride migration coefficient and electric flux of BFFN concrete decreased with the growth of the hydrate age and the increased of BFFN dosage.(5)In the large BFFN dosage composite cementitious system,which stimulated by cement-activator,the anhydrite play better stimulation effect,and the excitation effect increased with rhe increasing of anhydrite dosage,but the 90d compressive strength has a slight retraction phenomenon.The chemical bonding water content of composite cementitious material hydration hardened paste was significantly lower than that of cement,and in large age,the chemical combined water content will decrease. |
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