Effect of alternative silicon sources on alkali-activated carbon steel slag binder and silicon sources substitution mechanism

The high cost and carbon footprint of conventional alkali activator (sodium silicate) limit the wide-scale adaptation of alkali-activated materials. During the production of sodium silicate(SS), carbonate and silicate need to be calcined at 1400 °C, which is not environmentally friendly. In order to improve the sustainability of the activator, 10% SS was reduced in this paper. The effect alternative silicon sources (ASS) on the mechanical properties of alkali-activated carbon steel slag (CSS) prepared at room temperature were studied when the modulus is 0.5 and 1.0, and the mechanism of silicon source substitution was discussed by means of microscopic characterization. The substitution amount of ASS was 10% of the total CSS amount. ASS included waste glass powder (WGP), rice husk ash (RHA), diatomaceous earth (DE), diatomaceous earth analytical reagent (DEAR), and silica fume (SF). Microscopic characterization methods included X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry and differential thermogravimetry (TG-DTG), and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). The results show that the effect of ASS depended on the structure of SiQ n, and is affected by the initial modulus of the activator. The compressive strengths of the low modulus samples are lower than that of the high modulus samples, while the effect of silicon source substitution is the opposite. However, the effect of SF is less affected by the initial modulus, and the 90d compressive strength of low modulus and high modulus differed by only 8%. 10% SF substitution can save at least 48.28% of industrial SS. SF is an economic and effective ASS, which can provide a better ecological choice for the production of alkali-activated CSS cementitious materials.