| Nickel slag is a kind of granulated blast furnace slag during nickel metal smelting.The molten state nickel slag is cooled by wind naturally or water quickly.In terms of element composition,its SiO2(?50%)and MgO(?30%)content is very high,therefore,it is also called high silicon-magnesium nickel slag(called ?nickel slag? briefly).If nickel slag is used as cement admixture,metallurgical slag can be utilized largely.Currently,basic physical and chemical properties of nickel slag is researched plainly,besides,existing form of nickel slag in hydrated cement and effect of nickel slag on cement long-term hydration characteristic are focused barely.In this paper,the feasibility of nickel slag using as cement admixture is researched,including basic physical and chemical properties,long-term consistency with hardened cement paste and activation methods which are suitable for cement admixture based on nickel slag.In this paper,the grindability and fragility of NS-W and NS-A were researched firstly and were compared with steel slag and Portland clinker.The results show that four materials fragility order is that NS-A<steel slag<Portland clinker<NS-W and grindability order is that steel slag<NS-A<Portland clinker<NS-W.NS-A bond work index(28.5 kW.h/t)is 1.2 times larger than NS-W(23.3 kW.h/t).From microanalysis,NS-W structure is loose and forsterite fringes of the crystalline network is vague.Besides,NS-W chemical composition distribution is symmetrical.NS-A structure is compact and enstatite fringes of the crystalline network is visible.Metal ions such as Fe and Cr,aggregate partially in NS-A.The crystal structure and element distribution difference result in grindability difference.The effect of nickel slag content and fineness on Portland cement hydration characteristic was also researched.The results show that the particle density of solid powder raw materials increases with nickel slag fineness,but decreases as nickel slag content increases.An increase of nickel slag replacement causes a decrease of hydration heat,but an increase of nickel slag fineness can improve hydration heat.The compressive strength and flexural strength of the hardened cement mortars decreases as nickel slag content increases.The volume stability of hardened cement paste is qualified.The volume expansions of sample incorporating nickel slag of different fineness focus on 10 days.The volume expansions of sample incorporating >0.300 mm particle size nickel slag in the series of NS-A and <0.075 mm particle size nickel slag in the series of NS-W is obvious.When the samples are cured in 20? water and standard curing,the volume expansions of sample focus on 10 days.Meanwhile,volume expansion trend of sample incorporating less content nickel slag is similar to plain sample.With room temperature and constant humidity curing,drying shrinkage value of plain sample is obviously large than samples which incorporate 30% NS-A and 30% NS-W.The effect of nickel slag and silica fume on Portland cement hydration characteristic was also researched.The results show that the best proportion of raw materials is clinker: nickel slag: silica fume: gypsum=85%:5%:5%:5%.Its 28 d compressive strength is 67.1 MPa and 7 MPa larger than blank sample compressive strength.When it carries on hydration reaction,the peak of induction period hydration heat is 0.19379 J/g and the acceleration period is 0.25262 J/g.When curing at 28 days,hardened cement paste's 2-50 nm micropore proportion is 51%.Meanwhile,C-S-H gel is filled in hardened cement paste and AFt develops needlelike structure which compacts pores and improve strength.Last but not least,the matching of nickel slag with fly ash and mineral powder was also researched.The results show that best matching fineness of nickel slag-fly ash is 15.26 ?m-15.01 ?m and best matching fineness of nickel slag-mineral powder is 15.26 ?m-15.61 ?m.In terms of compressive strength and flexural strength,the best matching fineness of nickel slag-fly ash-mineral powder is 27.15 ?m-15.01 ?m-12.45 ?m and 17.81 ?m-11.86 ?m-12.04 ?m. |
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