Effect of Magnesia Whisker on Mechanical Property of Set Cement

Study was conducted on the effect of MBW, a magnesia whisker, on the basic performance of cement slurry and the mechanical property of the set cement, with the aid of XRD, MIP and SEM. It was shown that addition of 1%-5% MBW into oil well cement slurry generally had no effect on the density and thickening time of the slurry. The mobility of the slurry, however, was reduced with the addition of MBW, but can be improved by the treatment with USZ, a drag reducer. With the addition of MBW, the compressive strength and flexural strength of the set cement were apparently enhanced. At 80℃, the 1 d, 3 d, 7 d and 28 d compressive strengths of a cement slurry treated with 4% MBW were 8.3%, 15.4%, 21.5% and 18.8% higher than that of the base cement slurry, respectively; the 1 d, 3 d, 7 d and 28 d flexural strength of the cement slurry (containing 4% MBW), on the other hand, were 9.4%, 19.4%, 13.1% and 0.3% higher than that of the base cement slurry. MBW is an inert additive, which fills in the detrimental pores in set cement, hence improving the tightness thereof. As a kind of micro fiber, MBW plays a role in hardening and toughening set cement through bridging, pulling, stripping and breaking.