| In recent years,Portland cement is used in the construction industry;but its high energy consumption and heavy pollution are not consistent with the policy of green environmental protection.Compared with Portland cement,alkali-activated cementitious material with high strength,low hydration heat,good fast hardness,good mechanical properties and compact structure becomes a hot research topic in the construction industry in recent years.At present,there are a lot of research on alkali activated slag cement at home and abroad,but there is little research on alkali-activated nickel slag(a kind of industrial slag)cementitious material.Therefore,this paper mainly studies the influence of the kinds of alkali activator(NaOH,NaOH/Na2CO3,water glass)and alkali dosage,fly ash or incineration slag(i.e.,Municipal Solid Waste Incinerator Slag)single or both partially replacing nickel slag on the workable performance and mechanical properties of alkali-activated nickel slag cementitious material(JNC),and get the alkali-activated nickel slag-fly ash-incineration slag cementitious material.And the influence of the kinds of alkali activator and alkali dosage on the workable performance and mechanical properties of JNC-FL were studied.XRD,FSEM-EDS,IR,pore structure and other micro means were used to analyze the composition and microstructure of the hydration products of JNC and JNC-FL.Finally,the environmental cement brick with good volume stability were prepared by JNC-FL and granular incineration slag.Through the research of this paper,the main conclusions.of the study are as follows:1.When the alkali dosage of Na2O is 6%,compared with NaOH and NaOH/Na2CO3,the cement paste of the JNC activated by water glass(M=1.2)is more closely connected to the aggregate,whose average pore diameter and the total pore volume are the smallest,and the harmless pores and less harmful holes are the largest,so its mechanical properties are the best.Compared with NaOH,when using NaOH/Na2CO3 as activator,the hydration degree of nickel slag on the JNC is bigger.there are many types and quantities of hydration products on the JNC,such as calcite,the connection between cement paste and aggregate are denser,the average pore size and total pore volume are smaller,the ratio of harmless holes and less harmful holes are larger,so its mechanical performance is better.2.When fly ash or incineration slag respectively and partially replacing nickel slag,with the content increases from 0%to 40%,due to the activity of fly ash and slag is lower than that of the nickel slag,the setting time of JNC is prolonged,the flexural and compressive strength of JNC are reduced(when the dosage of fly ash or slag is 15%,the mechanical properties of JNC decreased less),but fly ash or slag can improve the bleeding performance of JNC.When 15%fly ash and 15%slag are substituted for nickel slag,its mechanical properties is better than that of 30%fly ash or 30%slag respectively and partially replacing nickel slag.3.In the JNC-FL system,when the dosage of NaOH or water glass(M=1.2)increases in the range from 3%to 8%,the flexural and compressive strength of JNC-FL increase and its setting time is shortened.While the dosage of alkali(namely Na2O)is constant,the flexural and compressive strength of JNC-FL taking water glass as activator is better than that of NaOH as activator.When the module of water glass is 1.2 and the dosage of alkali by Na2O is 8%,the flexural strength and compressive strength of JNC-FL for 28d age can reach 7.34 MPa and 50.31 MPa respectively,which reaches the strength grade of P.O 42.5.4.The metallic aluminium of granular incinerator slag in the alkaline environment can generate hydrogen is the main reason for the early cracking of environmental cement bricks.Alkaline solution pretreatment can be used to remove the metallic aluminum in granular incinerator slag.Pretreated granular incinerator slag and JNC-FL can be used to prepare the environmental cement brick with good volume stability and no heavy metal leaching. |
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