Research On The Mechanism And Properties Of Alkali-activated Nickel Slag

Nickel slag is a kind of industrial waste produced during the production of nickeliron alloy.NaOH with different dosages and water glass with different modulus are used to alkali-activate blast furnace nickel slag and electric arc furnace nickel slag.The aim is to analyze the reaction mechanism and reaction process of alkali-activated nickel slag,and the macroscopic performance of alkali-activate blast furnace nickel slag concrete.Alkali-activated blast furnace slag concrete and plain cement concrete are used for reference.Meanwhile,a preliminary attempt is made to carry out the modification of alkali-activated electric arc furnace nickel slag.The main research contents and conclusions are as follows:(1)Blast furnace nickel slag which is alkali-activated by NaOH and water glass can produce only one kind of crystal product,namely str?tlingite.The addition of NaOH content and the modulus of water glass are beneficial to the formation of gel products.However,the increase of water glass modulus can result in the significant decrease of str?tlingite.(2)The expression of the gel products of alkali-activated blast furnace nickel slag can be written as(N,C)-A(M)-S-H.The Ca/Si of the gel products decreases,and the Al/Si increases with the addition of NaOH content.When water glass is used as the activator,the Ca/Si and Al/Si both decrease with the increase of water glass modulus.(3)High alkalinity can accelerate the initial reaction of blast furnace nickel slag.However,the growth space of the reaction products would be limited at late age when the alkalinity is too high.Silicate can promote late reaction,but the high content of silicate causes the actual alkalinity to decrease,which is not conducive to the reaction,especially the early reaction.(4)The alkalinity is the key factor to determine the mechanical property and antipermeability of the alkali-activated blast furnace nickel slag concrete.What’s more,the high alkalinity is the basis of the promotion effect of silicate on the reaction.However,for the alkali-activated blast furnace slag concrete,a high content of silicate is beneficial to improve the mechanical property and anti-permeability of the concrete,while too high alkalinity may seriously restrict its performance development.(5)The higher the alkalinity,the higher rate of the shrinkage of alkali-activated blast furnace nickel slag concrete at early age.Silicate contributes to the shrinkage of alkaliactivated blast furnace nickel slag concrete at late age.The shrinkage value of alkaliactivated blast furnace nickel slag concrete is obviously less than that of the corresponding alkali-activated blast furnace slag concrete when water glass is used as the activator.(6)Under the condition of the equal compressive strength,the late performances of alkali-activated blast furnace nickel slag concrete are better than those of the plain cement concrete.Furthermore,the late-age performances of alkali-activated blast furnace nickel slag concrete are superior to those of the plain cement concrete when the the activator is water glass.(7)The activity of electric arc furnace nickel slag is very low.The only reaction product is the gel,whose contents of Ca and Al are both very low.The performance of alkali-activated electric arc furnace nickel slag can be improved with the addition of blast furnace slag or steel slag.