Mechanical properties and mechanism of wollastonite fibers reinforced oil well cement

Abstract

Wollastonite fibers (WFs) were used to reinforce the oil well cement (OWC). The compressive strength, flexural strength, tensile strength and stress–strain curves of WFs reinforced oil well cement pastes (OWCPs) were studied. The strengthening mechanism was studied by analyzing WF-reinforced OWCPs with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), nitrogen adsorption method (BJH), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results show that compared with those for pure OWCP, the compressive strength, flexural strength and tensile strength of the OWCP with a WF content of 15% cured at 90 °C for 7 days increased by 34.64%, 98.79% and 46.46% respectively. In addition, the toughness of the OWCP with a WF content of 15% improved. The microstructure analysis showed that a good interface adhesion appeared between the WFs and OWCP due to the presence of chemical bonds. The addition of WFs reduced the content of cement hydration products, namely lamellar CH, by reacting with CH to form hydrated calcium silicate (C-S-H), which improved the mechanical properties of the OWCPs. Adding WFs improved the pore structure distribution of the OWCPs. The improvement in the toughness of the OWCP with a WF content of 15% was attributed to the “crack bridging” and “fiber pull- out” toughening mechanisms.