STRUCTURALLY FAILED CHIMNEY REINFORCED WITH ENGINEERED CARBON FIBER WRAPPING SYSTEM

A concrete chimney in a sugar refinery plant was at high risk of collapse, so Industrial Access carried out repairs designed to rehabilitate the structure to stable condition. Cracks and holes in the concrete exterior were filled, old platforms were replaced, and a carbon fiber system was installed to reinforce the concrete exterior. Strategic repair solutions restored this failing chimney to its operational efficiency and ensured its safety and reliability.

Industrial Access (IA) was first retained to perform a Class II condition assessment for a 250’ concrete recovery boiler chimney at a sugar refinery plant, all in accordance with ASCE Chimney and Stack Standard Guidelines. The visual exterior inspection revealed severe concrete spalling, heavy efflorescence buildup, corrosion, and wear around tension bands. The team discovered a number of safety hazards, such as missing bolts, air vents, failing mortar joints between bricks, and oxidized, disconnected platforms and ladders. The chimney was experiencing exterior delamination, cracking, and spalling from years of use, environment, and acidic flue gas transmission. The structure was determined to be in a very poor condition, putting it at risk of falling, and IA’s primary recommendation was to demolish the structure.

However, the facility had very specific needs, limitations, and a short outage window, prompting IA to carry out emergency measures first in order to minimize falling object hazards and slow down the rate of deterioration. IA’s expert team of engineers determined that the most effective solution would be installing a carbon fiber reinforcement system on the exterior of the structure. IA was set to perform all external repairs while the chimney remained in operation.

In order to perform exterior repairs, IA assembled the frame of the moving scaffold, utilized a crane to erect the scaffold against the chimney, and anchored it to the chimney shell. Then, an external hoist, a mast climber, was built and installed around the structure, enabling a 360-degree access to stack exterior.

First, the cracks in the exterior shell of the chimney had to be repaired. IA crew used 5000 psi hydro blasting to remove softened and loose concrete. Once the unsound concrete particles were cleared, IA moved on to repairing the empty cracks. Every void in the windscreen was filled with repair mortar. Quikrete Shotcrete was used for larger cracks, and smaller voids and rough surfaces were smoothed over with a Quikrete stucco base coat. This treatment was designed to restore structural integrity and ensure a smooth surface of the chimney.

Once the shell surface was cleaned of dust and bond inhibitors, IA prepped the chimney for a carbon composite system by applying special primer and polymer. Then, CarbonSeal concrete carbon fiber reinforcement was wrapped around the chimney exterior. CarbonSeal urethane topcoat was applied over the wrap to protect it from exposure to ultraviolet radiation and chemicals. This carbon fiber repair system is a single-layer, lightweight, flexible, corrosion resistant reinforcement solution with low thermal expansion, appropriate for smokestacks, silos, and tanks in any industry. CarbonSeal serves to strengthen structure integrity and provide elastic stiffness necessary to keep a stack in an operating condition.

Once the concrete shell was repaired, IA removed the old platforms and replaced them with newly-fabricated ones, coated in A36 steel. The crew installed railing at the chimney top, new ladder, safety gate, and a climb fall restraint system. A flash coat of gunite was applied throughout the interior of the chimney. This coating will protect the structure from high temperatures and corrosive flue gas effects.

This repair enabled the facility to carry on with production as scheduled. After the work was completed, IA offered the client additional recommendations for further repairs that would protect the chimney from damage and improve its condition and efficiency. This carbon wrapping solution was initially intended to be a temporary repair; however, five years after, the chimney remains in good operating condition, delaying the urgency to demolish the chimney and allowing the plant more flexibility to plan ahead.