September 30, 2011

TAYLOR HAZELL ARCHITECTS LTD.

Lake Erie’s Point Abino Lighthouse, built in 1918, undergoes an extensive restoration, which includes concrete repairs.

FEATURE | Concrete/Masonry

Phoenix Restoration works on Point Abino Lighthouse in Fort Erie, Ontario

DON PROCTER

correspondent

When it comes to testing the mettle of a building material, there’s nothing quite like exposing it to the swells and storms of a large body of water.

Take the near century-old concrete Point Abino Lighthouse built on a rocky shelf below the high water line of Lake Erie as an example. When the lake is at low ebb, a person can walk around the lighthouse off the shores of the Town of Fort Erie. But fierce lake swells can top nine feet, crashing against the sides of the 95-foot tall structure, making access impossible and wreaking havoc on the structure.

An early example of cast-in-place reinforced concrete structure, the lighthouse is undergoing a $1.3 million restoration. Most of the restorative work involves concrete repairs.

“When you think about it, this was quite a bold concept at the time because the lighthouse was first built in wood, then filled with concrete,” says Charles Hazell, project architect, Taylor Hazell Architects. “It was a cutting edge project at the time, which is a reason for its national significance.”

“Back then there were fairly limited measures taken to protect the building from future deterioration,” explains Beau Gaudreau, project engineer, Read Jones Christoffersen, the project’s structural engineer.

Still, the concrete structure has “held up very well,” he says, largely because of the mass of the concrete and the depth of the embedded reinforcing steel.

In many areas the reinforced concrete is 12 inches thick with three to four inches of concrete cover over the reinforcing steel. For that reason, RJC’s repair method focuses on localized repairs of concrete in areas where corrosion of the reinforcing steel has caused concrete delamination.

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The first step has been to remove by hand the existing paint coating on the exterior to get a close inspection of the concrete’s condition. To pinpoint the localized deterioration on the structure, a simple acoustical test is done consisting of sounding the surface using a hammer to locate hollow areas, says Gaudreau.

TAYLOR HAZELL ARCHITECTS LTD.

From left, Jason James, Phoenix Restoration; Beau Gaudreau, Reed Jones Christoffersen; and Charles Hazell, Taylor Hazell Architects, review a designated repair area.

“With experience, it is possible to determine where these hollow-sounding areas correspond to concrete delaminations resulting from rebar corrosion.”

Jackhammers remove most of the concrete beyond the depth of the embedded reinforcing and sandblasting takes off the corrosion on rebar. Once the area is clean, a high-performance self-consolidating concrete patch material is placed with a board form finish to match the original appearance.

Gaudreau says the concrete repair material contains silica fume, a byproduct of producing silicon metal. It increases the density of the material to better protect the embedded reinforcing steel.

Repair methods have improved since the lighthouse last underwent concrete repairs 20 to 30 years ago, says Gaudreau, pointing out that today’s methods will perform well for a long time.

“In general, the previous repairs were shallow-depth repairs, and in many cases they failed,” he says.

Once concrete repairs are completed, an elastomeric protective coating will be applied to the entire structure to ensure porous areas of the original concrete (aggregate used in some areas was as big as a baseball) keep out moisture. “It’s the primary line of defence.”

While concrete repairs represent the lion’s share of the work at the landmark lighthouse, fragments were found of the original steel windows and they are being used to replicate the steel windows. Bronze handrails are being installed, and the lantern is being restored along with the access ports and fog horn. A passive flood control system is being introduced in the basement to manage water entry during high water, says Hazell.

The restoration project, which started in late May, is being done by general contractor Phoenix Restoration Services. Substantial completion is slated for the beginning of October, prior to the storm season.

Built in 1918 in a classical revival style, the lighthouse is a designated National Historic Site. Back then, the beacon helped guide ships around the rocky shoals at the eastern end of Lake Erie. It was decommissioned in 1995.

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