Elucidating the mechanical property-enhancement mechanism of ferrite in oil-well cement using spherical ferrite

High-ferrite oil-cement (HFOC) has attracted extensive research interest owing to its excellent mechanical properties and corrosion resistance. However, it is difficult to distinguish ferrite and its hydration products in cement paste. Therefore, establishing the mechanism of improvement of the mechanical properties of Portland cement upon the addition of ferrite is challenging. In this study, spherical ferrite (SF) was prepared via jet granulation to explore the mechanism of hydration and improvement of mechanical properties of oil-well cement pastes upon the addition of ferrites. XRD results showed that the crystal structure of the SF is consistent with that of ferrite. Phase analysis of the hydration products revealed that the hydration products in the AFm phase gradually covered the SF particles entirely during the early hydration reaction and transformed into cubic crystals C ₃(A, F)H ₆ during the subsequent hydration reaction. The assessment of mechanical properties demonstrated that the compressive and tensile strengths of the oil-well cement paste increased by 11.7 % and 17.5 %, respectively, upon the addition of 4 % SF. Moreover, the addition of SF reduced the elastic modulus of the cement paste. The mechanical properties enhancement mechanism of SF in oil well cement involves participating in the hydration process of oil-well cement and consuming fracture energy. This study provides theoretical support for the development mechanism of mechanical properties of oil-well cement.