Carbon fiber used to restore historic structure

Carbon fiber used to restore historic structure
Posted on 12/28/2020
Carbon fiber material to help rehabilitate the historic Sunset Heights Reservoir.

The Sunset Heights Pump Station and Reservoir is made up of two tanks with the capability of holding up to eight million gallons of water. It is one of the city’s oldest structures, and it plays an important role in how El Paso Water distributes water to different areas of the city.

In March, the tremors of a 5.0 magnitude earthquake in Mentone, Texas damaged the decades-old structure, causing it to leak. Now, EPWater is using a relatively new technique to the water sector to rehabilitate large facilities with reinforced carbon fiber.

Initial plans approved by the Public Service Board to make upgrades to the reservoir were expedited shortly after EPWater was able to identify the extent of the damage, some of which occurred prior to the earthquake, while the tremor caused further structural damage.

“There were cracks large enough to see roots making their way into the tank itself,” said Gilbert Trejo, EPWater Chief Technical Officer.

Repairing the damage

 To remedy the damage, Consor Engineers is using carbon fiber to reinforce the inside of the reservoir and its beams. Trejo said it is a method commonly used in the oil refining industry to rehabilitate tanks. It is an innovative approach to reinforce steel that is often corroded and weakened by corrosive environments.

“This is the largest application of carbon fiber we’ve ever used,” Trejo said.

First, the cracks are sealed with cement grout, concrete, or a high-strength mortar coating, then the carbon fiber is cut into large strips and applied to the floor, walls, and beams. Contractors pour a thick, clear resin over the material and spread it evenly with a roller brush.

“The best way to think of it is like when athletes wrap their ankles with tape to give additional support and hold the ankle in place,” Trejo said.

Once the resin is applied, it seeps through the carbon fiber wrap and hardens, creating a high-strength bond between the carbon fiber and the concrete.

Testing the strength

Unlike regular concrete testing, where a cylinder is extracted from the new concrete and crushed to test its compressive strength, contractors perform a ‘pull-out test’ to gauge the carbon fiber’s bond to the existing concrete. Small cylinders are bonded into the fiber material with resin during installation.  After curing for several days, a machine is used to pull the small cylinder out of the fiber wrap.  The force required to pull out the cylinder corresponds to the strength of the bond.

What was once a structure with visible wear-and-tear will soon be able to continue functioning as designed for decades to come.

“Because the tanks were in need of dire repairs, this was the best technology to use,” Trejo said.

Moving forward, EPWater will consider the carbon fiber technique with other projects and will modify design standards to include a level of earthquake protection. Tearing down the pump station and reservoir was not an option for the utility because of its location and the impact it would have on the operation of the water distribution system. This rehabilitation project allows EPWater to maintain service to the area while preserving the historical significance of the site.

The Sunset Heights Reservoir is expected to be in full use by the summer of 2021.

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