October 13, 2008

Sustainable Building Practices

Concrete soil solidification and stabilization technology helps reclaim industrial sites

Brian Martin

correspondent

Who says the sins of the father are not visited on the son? Certainly not the construction and development industries.

Particularly in urban areas such as Metro Vancouver, Grandpa’s old habits are coming back to haunt builders.

They discover this when they go to redevelop a brownfield location.

That is an area that has been built upon by a previous generation.

The redevelopment of the former industrial properties around Coal Harbour or False Creek in Vancouver are perfect examples.

Those lands were used for decades by sawmills, foundries, shipping companies, railways and you-name-it.

The ground under those properties is often soaked with dangerous contaminants and nothing new can be built on those sites until the contamination problem is solved.

That can be extremely expensive.

Traditionally, it has involved removing the contaminated soil and trucking it off to a distant site to be cleaned at considerable cost.

Now the cement industry has a system that can help solve the problem.

At the same time, it is more environmentally sensitive than trucking contaminated soil around the city.

It is called soil solidification and stabilization.

Andrew Vizer, director of engineering for the Western Region of the Cement Association of Canada explained the system.

“Basically we mix cement into the soil. Depending on the type of pollution, the site will be stabilized either chemically or physically and become usable,” he said.

“A big advantage is that this is a technology that does not involve removing the contaminated soil to somewhere else for cleaning.”

Depending on the site and the conditions, the contaminated soil is either removed and mixed with cement or the cement is directly mixed in the soil in-situ.

Not hauling the material around and minimizing environmental impact can earn a developer LEED points.

LEED is a North America wide points-based system for judging the environmental sustainability of new construction.

It is something that is being called for on virtually all new government construction, as well as on many private developments.

When it comes to the energy efficiency of actually producing the cement, which is the key ingredient in the manufacture of concrete, the industry has already made huge steps.

It has managed to reduce the CO2 emissions from concrete plants by around 30 per cent since the industry started to improve its production efficiency in the early 1990s.

Another very important area of research and development for the Cement Association has been the actual energy efficiency of concrete buildings.

“Buildings use an horrendous amount of energy – both for heating and for cooling,” said Vizer.

“Our strategy has been to contribute a technique, which has been known in the mechanical world for a long time.”

The system he is talking about involves using the thermal mass of a concrete building to assist in heating and cooling.

It is something, he said, that has been around for a long time, but there have been a lot of skeptics.

Vizer explained that it involves an active mechanical system working with the thermal mass to decrease the amount of heating and cooling involved.

For example, in the case of a concrete building facing south, heat will be captured during the day as the concrete heats.

It will then be stored and let out as needed.

This involves pumping either hot or cold water through pipes imbedded in the concrete slabs.

Such a system is being used in the massive Olympic Athletes’ Village currently under construction in Southeast False Creek.

The association has carried out simulated studies based on five Canadian cities – Vancouver, Regina, Toronto, Montreal and Halifax.

The association used commercially available software and the study assumed a four-storey rectangular building of 41,979 square feet.

The simulated tests show that 90 per cent of the cases show a cut in heating requirements.

Sixty per cent showed reduced heating requirements and more than 90 per cent of all simulated cases experienced reduced peak heating and cooling demand.

Closer to home, the cement association has recently completed a three-year study at the University of B.C.

The study was done in conjunction with the university’s sustainability office and Stantec Engineering.

It compared an existing older building at the university with traditional mechanical systems to a new building using a radiant system, imbedded in its thermal mass.

“The result was a 50 to 60 per cent energy savings,” said Vizer.

“Obviously this holds tremendous potential.”

One challenge, he said, is the amount of education still required by the design community.

“There are only a handful of mechanical engineers who understand how to design with this,” Vizer explained. “Luckily we have some very good ones in Vancouver.”

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