UBC Reports | Vol. 47 | No. 16 | October 18, 2001

Spray strengthens structures

Application prevents corrosion and contamination

A UBC civil engineering professor is testing a revolutionary polymer spray that is expected to double the strength of aging bridges at half the cost of traditional repair techniques.

Prof. Nemkumar Banthia developed the high performance fibre reinforced polymer (FRP) spray being used on Safe Bridge near Duncan.

He and a team of UBC students and researchers, with engineers from the B.C. transportation ministry, applied the spray to the 46-year-old bridge over a period of five days. The ministry committed $60,000 to test the new technology on the six-metre bridge with a view to using it for future infrastructure repairs.

The spray coating, composed of separate components of fibre and polymer applied at high-speed, is a novel structural rehabilitation technique designed to protect the bridge's concrete girders from corrosion, increase the structure's longevity and protect it against seismic damage.

"The spray application was very successful," says Banthia. "After the facelift, the bridge should be twice as strong and be able to absorb three times as much energy during an earthquake."

With its new FRP coating, Safe Bridge is now a "smart" bridge. Both the structure itself and the polymer coating carry fibre-optic sensors that transmit data by the Internet. These signals will help Banthia and his team to monitor the coat's effectiveness from campus.

The data will also allow engineers to study the bridge's performance in an earthquake and, afterwards, use the sensors to assess any damage to the bridge.

In lab tests against existing repair techniques, the FRP spray coating proved to be the strongest method of bridge deck repair.

The technique is estimated to cost half the amount of traditional steel jacketing and a third less than fibre-reinforced polymer jacketing.

Unlike steel jacketing, which corrodes over time, FRP spray will not corrode, adding to long-term cost savings, but Banthia explains that the real savings will be in the minimized repair times and traffic disruptions.

The versatile repair technique lets the user control the fibre content making it ideal for refitting other construction surfaces such as steel and timber, and customizing the repairs on any structure.

Besides strengthening, FRP spray can be used to prevent corrosion in high chloride environments such as the Hibernia oil drilling platform.

It can also be used to protect water supplies from contamination by creating an impermeable lining for containers like hog waste manure tanks.

The FRP spray and application technique was developed in conjunction with Intelligent Sensing for Innovative Structures (ISIS) Canada, a Network of Centres of Excellence program headquartered at the University of Manitoba.