Wet-mix shotcrete is more commonly used for high-production shotcreting applications than for repair jobs. But a Chicago-area contractor has designed and produced a wet method shotcrete machine specifically for repair work. The machine mixing chamber also is a pressure vessel connected to a small (85 cfm) air compressor. Compressed air pushes mortar or pea gravel concrete through a hose and nozzle at a steady rate.


Agitators in the shotcrete mixing/pressure tank conform to the tank shape. Rubber wipers on the blades direct all material to the outlet and wipe the inside of the tank clean. The nozzleman can start or stop shooting by turning a valve on the nozzle. Also on the nozzle are valves for compressed air and adding an accelerator.


The unit has been used for repair of bridges, tunnels, the underside of parking decks, and concrete curbs and gutters. One of the more challenging jobs was repairing huge concrete counterweights for an Illinois Central Gulf railroad bridge over the Chicago River. Freezing and thawing cycles had caused edges of the counterweights to crack and crumble. This affected the delicate balance needed for the bridge to raise and lower smoothly. To correct the problem, a shotcreting crew restored the edges by building up several layers of shotcrete.