Source: Associated Press
Publication date: 2009-10-01

Not only did it minimize the environmental impact on an adjacent wetland, what may be the first-ever application of a lightweight cellular concrete product on an Ontario road saved time and money and lessened inconvenience to adjacent residents, say Peel Region officials. Some 950 cubic meters of the lightweight concrete was poured along a 120-metre-long stretch of Dixie Road in Caledon in late August by Calgary-based Cematrix Cellular Concrete Solutions,the proprietary developer.

Rather than pouring concrete from a waiting convoy of ready-mix trucks,the concrete was sprayed into place by assistant project manager Brad Garity operating a large hose attached to a mobile command mixing centre where water, a foaming agent, compressed air, and Portland cement-from an adjacent 30-ton silo - were mixed together. Over a two-day period the lightweight concrete was poured to a depth of 650 millimeters and then topped up with granular material and asphalt. Within about two weeks the road was reopened compared to the several weeks it would have taken with traditional construction, says Barry Mulcahy,a project manager with Peel's transportation division. "We're always looking for innovative solutions," says Mulcahy.

While not considered a hazard to the driving public, the peat moss conditions in the adjoining wetlands have been the source of settling problems for several years, he says.

Traditional construction would have required considerable dewatering, extensive peat removal, the erection of sheet piling and then replacing the peat with granular material, says Bob Bower, vice president of Delcan Corporation Engineers, the consulting engineer: "It (traditional construction) would have been very costly." While basically a test experiment for Peel Region and the first application in Ontario, the concrete has been successfully used in Western Canada.

"We've been at this for 10 years," says Cematrix vice president Steve Bent. The lightweight concrete offers a cost-effective innovative solution to difficult and challenging road reconstruction in areas where there is weak soil, peat moss or where there is highly plastic clay, say Bent. Other applications include lightweight back fill for retaining walls and bridge abutments.

In Alberta where the below ground frost level can range from 10 feet in Calgary to 14 feet in Fort McMurray, it has been used as an insulator for utility lines, says Bent. Installation is rapid, with a capacity of from 20 to 150 cubic meters per hour in all conditions says Bent, noting the pouring hose can be extended a kilometer.