Alteration mechanisms of carbonated steel slag product under hydrochloric acid attack

The performances of carbonated steel slag products in hydrochloric acid (HCl) solutions with pH = 1-5 for 56 days were studied and compared to conventionally cured ordinary Portland cement (OPC) specimens. The compressive strength of specimens and pH of solutions were monitored at different ages. The final microstructural modifications at pH = 1 were characterized by micro tests including X-ray diffraction (XRD), the Rietveld method (QXRD), fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The ease of minerals to react with HCl was analyzed by thermodynamics. The micro test results revealed that carbonated steel slag products suffered more serious degradation than OPC. The alteration mechanisms of both included almost complete decalcification, dissolution of some crystallized or amorphous phases and the formation of silica gel. The thermodynamic analysis showed that ettringite had the highest potential to react with HCl while the CaCO(3)had the lowest ability among the mineral phases studied.