The ornamental design for concrete block insulation, as shown and described.
FIG. 1 is a front perspective view of concrete block insulation of my new design in a flat, unfolded configuration.
FIG. 2 is a rear perspective view of FIG. 1;
FIG. 3 is a top plan view of FIG. 1;
FIG. 4 is a bottom plan view of FIG. 1;
FIG. 5 is a right-side view of FIG. 1.
FIG. 6 is a rear view of FIG. 1.
FIG. 7 is a left-side view of FIG. 1.
FIG. 8 is a front view of FIG. 1; and,
FIG. 9 is a perspective of the concrete block insulation of FIG. 1 in an erected, folded configuration for installation into a concrete block.
The broken lines depict portions of the concrete block insulation that form no part of the claimed design. The broken lines in FIG. 9 depicting a concrete block represents environmental subject matter that forms no part of the claimed design.