September 30, 2011

NUNA INNOVATIONS

Concrete Canvas is a waterproof PVC membrane fused to a 3-D fibre mesh cloth impregnated with cement.

FEATURE | Concrete/Masonry

Concrete Canvas offers flexible construction options

PETER KENTER

correspondent

A new construction product offers users the ability to apply sheets of concrete-impregnated material anywhere from pipe exteriors to landscapes, creating a permanent concrete structure with a design life of 25 years.

Dubbed Concrete Canvas in Canada, the product was initially developed in Great Britain to help military operations erect rapidly deployable concrete structures. The material is distributed in Canada, Washington, Oregon and Alaska by Nuna Innovations, with headquarters in Squamish, British Columbia.

The product is a waterproof PVC membrane fused to a 3-D fibre mesh cloth impregnated with cement.

“On top of that is a woven geo-textile material that allows for hydration,” says Dan O’Kane, sales representative for the product. “Hydration is the scientific term for what you actually do with it — simply hose it down.”

The product is delivered in large rolls 5 mm to 13 mm thick, then cut to shape and size. Once wetted, the product begins to cure in about two hours, gradually hardening over a 24-hour period to permanently take on the shape specified by the user.

The most common construction uses for the product include pipe wrapping, ditch lining and erosion control.

NUNA INNOVATIONS

Concrete canvas was created in Great Britain and it has been tested for various Canadian climates.

“For a pipe application, you simply cut the canvas to size and wrap the pipe with an overlap, then wet it,” says O’Kane. “We’ve had great success using plastic cable ties to hold the canvas in place while curing.”

The advantages of wrapping a pipe with the product include the provision of extra weight to help the pipe bed itself more effectively, particularly in wet soils where pipes tend to float. Other benefits include secondary containment, pipe joint protection, abrasion and sag resistance, and chemical and corrosion protection. Because the product can be hydrated with salt water, the material can also be used in marine applications.

To build a concrete-lined ditch, sheets of the product are staked to the ground and shingled in the direction of water flow.

“For a larger ditch, you may want the sheets to fuse to each other across the ditch,” says O’Kane. “To achieve a concrete joint, you strip away some of the PVC to create concrete-to-concrete contact. You then screw the sheets to each other to set them in place.”

In erosion control applications, the product is used similarly, but needs to be anchored firmly to the top of the slope.

“We’ve found that the best way to anchor it is to wrap the canvas around a pressure-treated six-by-six, which is trenched and buried at the top of the incline,” says O’Kane.

Although used extensively in Europe since 2007, the product needs to be approved for various applications in Canadian jurisdictions. It is currently approved as a ditch liner and erosion-control product in British Columbia and approved as an underground mining product in Ontario, where it’s used to seal off unused mine passages to improve air flow.

“We’re currently applying to have the product approved for a number of applications, including temporary coverage of mine tailing ponds to prevent precipitation from adding to the volume of the tailings,” says O’Kane.

The company has also tested the product across a range of Canadian climates to advise users on how best to apply the material.

“For example, during a very hot and dry Canadian summer, we’ve found that it’s best to keep hydrating the product for a few hours to compensate for evaporation,” he says. “Once curing begins you can’t over-hydrate it.”

The product continues to be manufactured in Wales but O’Kane says that the company is working closely with a manufacturer to see the product produced in North America as well.

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