Dynamic Characteristics and Micro-Structures of Steel Slag Under the Influence of Oxidation Periods and Ph Values

Abstract

In order to improve the utilization rate of waste steel slag, using waste steel slag as geotechnical backfill material is an effective way to recycle steel slag. However, different from traditional soils, oxidation reaction of steel slag will occur under the combined action of humidity and air when waste steel slag is buried shallowly, and the different pH values of the backfill environment in the actual project also has a certain impact on the mechanical characteristics of steel slag. Therefore, two main factors of oxidation period and pH values were considered on the effect of dynamic properties of steel slag. Dynamic shear properties of steel slag were carried out by resonance column tests, as well as micro-properties of steel slag were carried out by scanning electron microscopy, X-ray diffraction, and nitrogen adsorption specific surface area methods. The results showed that with the increase of oxidation period, the maximum dynamic shear moduli of steel slag gradually increases, and the phenomenon of slow growth in the early and late stages and rapid growth in the medium period was shown. Both acidic and alkaline environments can increase the dynamic shear moduli of steel slag. The reason for the enhancement of the dynamic shear moduli of steel slag was that the hydrated calcium silicate gel, calcium hydroxide crystal and calcium alum (AFt) were produced in the oxidation of steel slag with air and water, in which hydrated calcium silicate and needle-like calcium alum were filled in the pores of steel slag particles, and a tight whole was formed under the action of hydrated calcium silicate. Therefore, the dynamic shear moduli of steel slag was improved.

Keywords: Steel slag, Oxidation period, pH values, dynamic shear moduli, damping ratio, Microstruct