Development of a High-Density Cementitious Rock-Matching Grout using Nano-Particles


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Title: Development of a High-Density Cementitious Rock-Matching Grout using Nano-Particles

Author(s): B.H. Green

Publication: Special Publication

Volume: 254


Appears on pages(s): 121-132

Keywords: colloidal silica; hematite; high density; high strength; rock-matching grout; silica fume; ultrasonic pulse velocity; viscosity modifying admixture

Date: 10/1/2008

This paper describes the development of a high-strength, high-density cementitious rock-matching grout mixture for use in a field project. This portland cement-based grout incorporated silica nanoparticles in the form of an ultra-fine amorphous colloidal silica (UFACS) along with hematite fine aggregate, silica fine aggregate, silica fume, water, and other chemical admixtures to match as closely as possible the given in-situ high-strength rock properties at a given field site. The new admixture, UFACS, was used as a viscosity-modifying agent to prevent aggregate segregation and was used to replace sodium bentonite clay, which frequently leads to a decrease in unconfined compressive strength. The resultant rock-matching grout (RMG) mixture was then placed in the field with over 65 individual batches to fill the annular space surrounding instrumentation packages previously placed in drilled boreholes. The resultant mechanical properties of this field-placed RMG included unconfined compressive strengths of 91.2 MPa (13,230 psi), hardened densities of 2680 kg/m3 (4,520 lb/yd3), and ultrasonic pulse velocities of 4.40 km/s (14,500 ft/s).