The ornamental design for a constructionblock, as shown and described.
FIG. 1 is a top elevational view of a construction block showing our new design;
FIG. 2 is a bottom elevational view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a front view thereof; and,
FIG. 8 is a rear view thereof.
The broken lines showing diamond shaped openings on the top (FIGS. 1 and 3) and circular shaped openings on the bottom (FIGS. 2 and 4) of the construction block illustrates environment only that form no part of the claim.