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The major objective of primary cementing is to provide zonal isolation in oil, gas, and water wells, i.e., to exclude fluids from one zone to another in the well.The high temperature and pressure in oil wells require a particularly resilient cement system.Recently, several research groups in oil and gas industry have begun to study the application of nanomaterials to mitigate problems in oil well cementing.Addition of nanoscale particles to cement paste can improve the functionality of the cement system providing a range of property improvements.The Youngs modulus of cement sheaths in oil wells should be as low as possible, while the tensile strength should be as high as possible to maintain the desired mechanical properties for cement sheath in oil wells.In this study, the Youngs modulus, E, tensile strength, σt and fracture toughness, KIC of neat Class G oil well cement paste with and without 0.2% (BWOC) nanopalygorskite were determined by use of the flattened Brazilian disk specimen.2ct=30 was selected for the loading angle corresponding to the flat end width.E was determined from the slope of the section before the maximum load, σt from the maximum load, and K1c from the local minimum load observed subsequent to the maximum load.Incorporation of nanopalygorskite enhanced the σt/E ratio and the fracture toughness leading to improved tensile properties, which seems to reveal more efficient performance of cement sheaths in oil wells.