Germanium(Ge),a waste residue leaching from zinc(Zn)smelting process,has potential cementitious properties and could be recycled as a cement supplement activated by chemical reagents.In this work,a test was conducted ...Germanium(Ge),a waste residue leaching from zinc(Zn)smelting process,has potential cementitious properties and could be recycled as a cement supplement activated by chemical reagents.In this work,a test was conducted to determine the hydration properties of Ge slag-cement-based composites with Ge slag(GS)/ordinary Portland cement(PC)contents of 0wt%,5wt%,10wt%,15wt%,20wt%,and 25wt% and water-to-binder ratio(w/b)of 0.4.The activators Ca(OH)2,AlCl3,NaAlO2,and Na2CO3 were mixed under 1wt%,2wt%,3wt%,and 4wt% dosages of GS weight.The composition and microstructure of the hydration products were investigated by the combined approaches of X-ray diffraction(XRD),thermogravimetry-differential scanning calorimetry(TG-DSC),scanning electron microscopy(SEM),and energy-dispersive X-ray spectroscopy(EDS).First,the GS cementitious property is attributed to the high content of CaSO4·2H2O.Second,the activators affected the acceleration performance in the following order:NaAlO2,Na2CO3,AlCl3,and Ca(OH)2.More importantly,the 28-day unconfined compressive strength(UCS)is 45.34 MPa at the optimum formula of 0.6wt% NaAlO2,15wt% GS,and 85wt% PC,which is 9.16% higher than the control.Thus,NaAlO2 is beneficial for the ettringite(AFt)generation,resulting in the C-S-H structure compaction.However,the Zn^2+ residue inhibited the AFt formation,representing an important challenge to the strength growth with curing age.Consequently,the GS could be recycled as a supplement to the cement under the activator NaAlO2.展开更多
This paper considers a cold standby repairable system consisting of twosupplemental equipments and a single repoirman. In the system, the failure distribu-tions and repair distributions of the two-supplemental equipme...This paper considers a cold standby repairable system consisting of twosupplemental equipments and a single repoirman. In the system, the failure distribu-tions and repair distributions of the two-supplemental equipments are assumed to beexponential distributions, but one supplemental equipment after repair will be “asgood as new” and the other one not. Under these assumptions, seme reliability in-dices are derived by using the geometric process and the method of supplementaryvariable.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51701094, 51834001, and 51574013)the key projects for the prevention and control of major accidents in safety production, China (No. Henan-0005-2016AQ)the Plan for Scientific Innovation Talent of Henan Province (No. 194200510010)
文摘Germanium(Ge),a waste residue leaching from zinc(Zn)smelting process,has potential cementitious properties and could be recycled as a cement supplement activated by chemical reagents.In this work,a test was conducted to determine the hydration properties of Ge slag-cement-based composites with Ge slag(GS)/ordinary Portland cement(PC)contents of 0wt%,5wt%,10wt%,15wt%,20wt%,and 25wt% and water-to-binder ratio(w/b)of 0.4.The activators Ca(OH)2,AlCl3,NaAlO2,and Na2CO3 were mixed under 1wt%,2wt%,3wt%,and 4wt% dosages of GS weight.The composition and microstructure of the hydration products were investigated by the combined approaches of X-ray diffraction(XRD),thermogravimetry-differential scanning calorimetry(TG-DSC),scanning electron microscopy(SEM),and energy-dispersive X-ray spectroscopy(EDS).First,the GS cementitious property is attributed to the high content of CaSO4·2H2O.Second,the activators affected the acceleration performance in the following order:NaAlO2,Na2CO3,AlCl3,and Ca(OH)2.More importantly,the 28-day unconfined compressive strength(UCS)is 45.34 MPa at the optimum formula of 0.6wt% NaAlO2,15wt% GS,and 85wt% PC,which is 9.16% higher than the control.Thus,NaAlO2 is beneficial for the ettringite(AFt)generation,resulting in the C-S-H structure compaction.However,the Zn^2+ residue inhibited the AFt formation,representing an important challenge to the strength growth with curing age.Consequently,the GS could be recycled as a supplement to the cement under the activator NaAlO2.
文摘This paper considers a cold standby repairable system consisting of twosupplemental equipments and a single repoirman. In the system, the failure distribu-tions and repair distributions of the two-supplemental equipments are assumed to beexponential distributions, but one supplemental equipment after repair will be “asgood as new” and the other one not. Under these assumptions, seme reliability in-dices are derived by using the geometric process and the method of supplementaryvariable.
