Mechanical properties of hybrid short fibers reinforced oil well cement by polyester fiber and calcium carbonate whisker

In the present work, a novel fiber hybridization containing PET fiber and CaCO3 whisker is developed to improve the multiscale cracking resistance, as well as to boost the toughness and mechanical performance of cement pastes. The mechanical properties, microstructure, the uniaxial and triaxial compression of hybrid fiber reinforced oil well cement pastes are investigated. The results indicate that after the introduction of mono PET fiber, the flexible strength and tensile strength were increased by 19.4% and 40.1%, but the compressive strength was decreased by 11.5%. Therefore, the CaCO3 whisker combined with the PET fiber is used to enhance the compressive strength of the cement matrix. Because PET fibers and CaCO3 whiskers are different in size, elasticity modulus and length-diameter ratio, the hybrid fiber can effectively interact with micro to macro cracks at multiple load stages. Hence, the hybridization contributes to enhancing multiscale cracking resistance from the microscale to the macroscale level, and the capability coefficients index of the cementious material are improved by 450.7% and 284.5% compared with those of control samples, respectively, under confining pressure. Moreover, the strategy enables to reduce the production cost of the cementing sheath of oil and gas well, and other large-scale construction project applications.