A combination expansion shell and resin secured anchor assembly for installation in a mine roof opening including an elongated bolt having rebar attached to the upper end thereof and an expansion shell below the rebar. The assembly is inserted into a mine roof opening in the back end of which is positioned a resin and catalyst cartridge, the cartridge being ruptured by the rebar, allowing the resin and catalyst to gravitate downwardly between the opening wall and rebar, where they are mixed upon rotation of the bolt and rebar. The bolt is rotated a predetermined number of revolutions to obtain optimum mixing of the resin and catalyst, after which continued rotation of the bolt in the same direction causes outward movement of the expansion shell into gripping engagement with the mine roof.