Often the concrete element will exceed the typical 8-10 inch thickness. During deep concrete removal via hydrodemolition up to 16 inch can be removed in a single pass. After removing reinforcing or embedded objects (Fig. 1), we can repeat the process until the full thickness of the reinforced concrete section has been removed. To date, our record is 72 inches.
Deep concrete removal is required during total depth repairs. This can occur on beams or columns were all the concrete must be removed in order to make the repair and to reestablish the load caring capacity of the beam, column, or concrete element. Rampart has also prepared openings or penetrations in structural concrete in dams, locks, and nuclear containment buildings.
Hydrodemolition can be used to cut drainage slots in concrete barriers (Fig. 2) without significantly reducing the impact strength of the barrier. New drainage slots were required when the road surface elevation was increased.
Deep removal can also be used on mass concrete structures such as dam spillways where the slab thickness can exceed 24 inches. These slabs and surfaces are reinforced and often the coarse aggregate can exceed 5 inches. If the rebar is 3 inches below the surface and the specified minimum clearance under the rebar is 2 inches, an average of 8 inches of concrete would have to be removed.
Structures with large aggregate provide a unique challenge to hydrodemolition. If a 5 inch piece of aggregate is 1 inch below the surface, and the specification requires a minimum of 2 inch removal, the hydrodemolition would have to remove 6 inches of concrete to dislodge the aggregate to provide the 2 inch minimum removal. If only 3 inch average is removed, the 5 inch piece of aggregate would protrude into the minimum 2 inch removal plan. Understanding the size of the coarse aggregate in mass concrete structures in critically important when planning or specifying concrete removal.