In June of 2016, the South Carolina Department of Transportation (SCDOT) was in the midst of building a new interchange at the intersection of I-85/I-385 in Greenville, S.C. During construction, severe localized spalling was found on the cover concrete of one column of a two-column pier supporting the I-385 northbound ramp. Upon discovery, SCDOT and their consultant closed the ramp to all traffic until a detailed inspection could be made.
After inspecting the affected column, it was determined that immediate repairs were required before allowing truck traffic on the ramp. SCDOT and their consultants designed a traditional concrete jacketing repair where the 30-in. diameter column was enlarged to a square footprint. The emergency repairs were designed, approved and constructed in less than two weeks.
Post-repair inspection of all the columns and pier caps of the old interchange revealed various degrees of corrosion on the reinforcing steel, with the most severe occurring at construction joints. Cracks and small, localized delamination of sections of cover concrete were observed on many of the columns throughout the old interchange, including the column adjacent to the jacket-repaired column.
While these deficiencies were not severe enough to warrant extensive strengthening of the columns, they were treated as potential hazards to both the traveling public and the construction teams working around the structures. SCDOT and joint-venture design-build contractor Flatiron-Zachry sought an economical, high-strength alternative solution to confine the damaged sections of the columns until they were demolished during the eventual reconstruction of the interchange.
Milliken Infrastructure approached SCDOT and Flatiron-Zachry to learn more about the problem and to determine if their RenewWrap FiberReinforced Polymer (FRP) strengthening system could provide a quick repair for the deficient columns.
The RenewWrap system consists of high-strength carbon fiber fabrics that are coated in the field with epoxy resins and bonded to or, in the case of the column repairs, wrapped around the structure to strengthen the member being repaired. The thousands of carbon fiber filaments in the FRP fabric perform the same function as reinforcing steel bars, but with the added advantage of being non-corrosive, which allows for placement directly on the surface of the columns.
