Carbon nanotubes reinforced lightweight cement testing under tri-axial loading conditions

The low density enables lightweight cement to be an ideal candidate for petroleum drilling in depleted formations. Lightweight cement is able to tolerate more deformation due to its high strain capacity. The major challenge, however, is its relatively low strength properties. Carbon nanotubes (CNTs) have been used in multiple industries to improve the strength, strain capacity, and durability of materials. In this study, the effect of CNTs on the mechanical properties of lightweight cement under triaxial loading conditions was analyzed. Two different lightweight cement systems, foam and microsphere cements, mixed with multi-walled carbon nanotubes at the concentration of 0.5%wt. were investigated and compared to conventional cement. Young's modulus, compressive strength, brittleness and strain capacity were measured under elevated confining pressures. Permeability and splitting tensile strength were calculated based on test data. Results suggest that the addition of CNTs to the lightweight cements enhances the compressive and splitting tensile strength, Young's modulus, strain capacity and ductility, while it decreases the permeability. Moreover, Scanning Electron Microscopy (SEM) was employed to analyze the dispersion of foam, microspheres and CNTs in cement composites.