SGH determined that the cast stone damage was due to freeze/thaw deterioration exacerbated by a previous repair campaign that covered the cast stone, including mortar joints, with a coating which has a low permeability and thereby trapped water. We also conducted material testing and determined that cast stone in areas not subject to heavy water infiltration was generally in adequate condition, the concrete was good quality with a depth of carbonation consistent for the material’s age, and the embedded reinforcement did not show signs of extensive corrosion.
During the initial survey, SGH identified hazardous conditions, including spalled and loose materials. We worked with Black River Design and a contractor to remove falling hazards and to provide temporary weather protection.
SGH then assisted Black River Design in developing repair details and specifications for the replacement of severely-damaged cast stone materials and repair of other cast stone pieces. During the development of the repair design, SGH conducted in-house laboratory experiments to evaluate the effectiveness of mechanical and chemical methods to remove the repair coating. We also consulted on alternate coating materials and evaluated their effectiveness in replicating the coated cast stone appearance if the existing coating were retained.