Fracturing of Rock with Expansive Cement

by Charles H. Dowding, (Aff.M.ASCE), Assoc. Prof.; Dept. of Civ. Engrg., Northwestern Univ., Evanston, Ill. 60201,
Joseph F. Labuz, (A.M.ASCE), Grad. Student; Dept. of Civ. Engrg., Northwestern Univ., Evanston, Ill. 60201,

Serial Information: Journal of the Geotechnical Engineering Division, 1982, Vol. 108, Issue 10, Pg. 1288-1299

Document Type: Journal Paper


A study was conducted to determine the efficiency of a highly expansive cement (called Bristar) used to fracture rock and concrete. The 48-hour expansive pressure of the cement, calculated to be about 46 MPa (6700 psi), is independent of hole size when tested in steel, thick-walled cylinders. Because the pressure is constant, a scaling relationship of S/d emanates from elastic theory, where S is the spacing between boreholes and d is the borehole diameter. However, the rate of pressure development is a function of cement temperature; consequently thermodynamic considerations may be as important as hole spacing. At the same scaled distances, 38-mm (1.5-in.) boreholes fracture dolomite 24-48 hours sooner than 12.7-mm (0.5-in.) holes. Optimal spacings in dolomite ranged between 8 and 16 borehole diameters.

Subject Headings: Boring | Cement | Spacing | Cracking | Rocks | Steel | Walls | Cylinders

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