Mechanical properties and hydration mechanism of Jinchuan nickel slag filling cementitious material

In Jinchuan Mine, nickel slag was used to develop a new cementing material instead of cement to reduce the filling cost. In order to make nickel slag cementitious material better used in mine filling, it is necessary to study its mechanical properties and hydration mechanism. Firstly, the physicochemical analysis of the test material was carried out, and then the strength test was carried out on the basis of the analysis, the ratio of activator, specific surface area of the material and slurry mass fraction were determined. Finally, the hydration products and hydration mechanism of nickel slag cementitious materials were explored by XRD analysis, infrared spectroscopy analysis, differential thermal analysis, energy spectrum analysis and SEM micro-structure analysis, which provides a theoretical basis for its application in mines. The results show that the proportion of nickel slag cementitious material is m(nickel slag):m(desulfurization gypsum):m(carbide slag):m(sodium sulfate):m(clinker)=85:5:5:3:2; the optimum specific surface areas of nickel slag, desulfurized gypsum, carbide slag and clinker are 620, 320, 320 and 300 m2/kg, respectively; When the slurry mass fraction is 81%, it not only satisfies self-conveying, but also can prepare filling body according to 1:4 cement-sand ratio. The static compressive strengths are 3.46 MPa and 5.76 MPa for 7 d and 28 d, respectively, and the dynamic compressive strengths are 5.3 MPa and 12.5 MPa, tensile strengths are 1.53 MPa and 1.79 MPa, shear strengths are 1.19 MPa and 4.04 MPa, which all meet the requirements of the mine. Under the combined activation of alkali and sulphate, the crystalline material and amorphous of nickel slag are continuously depolymerization and dissolved, and hydration reaction takes place. A large number of ettringite and ettringite phases are formed, while irregular floc gel fills the gap. With the increase of curing age, the structure becomes denser and the strength increases. © 2021, Science Press. All right reserved.