Concrete for grouted riprap Type I shall be an approved batch per MAG Standard Specifications and shall develop a minimum 2,500 psi compressive strength within 28 days. Add 1.5 pounds per cubic yard FIBERMESH, or approved equal, fibrous reinforcing.
Wash the stone free of fines or soil which would affect the grout bond. The concrete grout shall be placed by injection methods by pumping under low pressure, positive displacement methods, through a 2-inch maximum diameter hose to ensure complete penetration of the grout into the stone layer. The voids at the surface, as detailed on the drawings, will not be grouted unless designated. Grout thickness shall be as follows:
Type Grout Thickness Max. Stone Projection
I 9 inches 4"
II 18 inches 6"
The maximum stone projection is the projection of the maximum size stone above the finished grout surface and is used to verify adequate grout thickness.
The operator shall be able to stop the flow and will place grout in the voids and not on the surface of the rock. Clean and wash any spillage before the grout sets. A "pencil" vibrator will be used to make sure all voids are filled between and under rock. The intent is to fill all voids from the subgrade level through the rock layer. In all cases, grout must penetrate to subgrade. The pencil vibrator may be used to smooth the appearance of the surface. The grout mix shall be stiffened and other measures taken to retain the grout in steep locations.
