Micro-damage external expansion bonding type building anchor bolt

The invention discloses a micro-damage external expansion bonding type building anchor bolt, and belongs to the technical field of building anchor bolts. A damage expansion body is arranged in the bolt, a plurality of damage expansion cavities are formed in the bottom end wall of the bolt, after a glue injection pipe drives damage expansion pieces to move downwards, the damage expansion pieces move to the damage expansion cavities, and due to the outward high-elasticity effect of the damage expansion pieces, the multiple damage expansion pieces are arranged on the portion, outside the damage expansion cavity, of the concrete hole wall in a buckled mode, in the extrusion friction process, acid damage liquid in the damage expansion pieces overflows, a certain acid damage effect on the concrete hole wall is easily achieved, and the friction shearing degree between the damage expansion pieces and the concrete hole wall can be improved.In addition, anchoring glue is injected into an overflow ball by theglue inject