Problem
A 18-inch (45.7cm) square concrete column supporting a critical pipe rack located in a refinery was deteriorating causing the concrete to spall, exposing the structural rebar to the elements. If left untreated the column would be in jeopardy of failure, causing an unplanned shutdown and extensive repair costs. The logistics and timing to replace the column would require months to complete and would significantly disrupt operations of the refinery.
Conditions
The assessment of the column within the refinery identified that the column had lost an estimate of 30% of it’s original load capacity, requiring immediate action to be taken to prevent the collapse of the overhead pipe rack which would cause a major disruption in operations.
Solution
The design solution was based on ACI 440.2R requirements for confinement strengthening of an exterior column according to requirements in the ACI standard. The damaged area was scored and grinded to remove the spalled concrete, rust and foreign matter. The exposed rebar was coated with a rust converter and epoxy sealant to protect, and effectively halt future corrosion of the rebar. The spalled areas were resurfaced to match the original column geometry using an epoxy based grout. Saturant epoxy was applied to completely encapsulate all four sides of the column over the 70? (1.8m) high repair zone. Engineered Uni-directional carbon fiber was then impregnated with the saturant epoxy system and applied with the fibers aligned in a vertical direction for flexural strengthening. The bi-axial carbon fiber was then wrapped in a circumferential manner to achieve full confinement for compressive strength. Within a matter of two hours the column was fully repaired and reinforced to provide adequate flexural and compression resistance.
Result
The defective area was reinforced, fully restoring the structural integrity of the column to it’s original design specifications. The Engineered structural composite repair system was completed without the need to shut down, thus saving the refinery significant costs that would have been incurred if the plant had been shutdown.
