Issue link: http://digital.canadawide.com/i/607779
DECEMBER 2015 | 17 PHOTOGRAPHY COURTESY ARMTEC 100-plus years without repairs if the right materials are used, "but the current approach says let's use coated rebar, and accept we'll have to repair it in about 30 to 35 years," says Richard Huza, director of business development at Salit Steel. Huza adds that this is why many P3 projects stop short at 30 years. Otherwise, he says, there is no reason a P3 should not last 50 or 60 years. Nonetheless, demand for stainless steel rebar has grown "400 to 500 per cent over the last five years," he says. U.S. states, including Texas, Louisiana, New Hampshire and Oregon are requir- ing that bridges in coastal regions use stainless steel. Structures with lots of elec- tronics, like hospitals, are now using stainless steel rebar. "With issues like stray current, it's easier to use stainless than use design to isolate conventional ferrous metal with a special design," Huza says. Stainless steel is also being used for light rail transit infrastructure and bridges in Alberta. Diagnosing the health of a section of reinforced concrete could become a more precise science with the help of an online database and some new software, says Roland Heere, a materials engineer at Metro Testing Laboratories. The company uses radar scanning to identify problems with rebar, however, there is still much to learn; which is where the online database comes in. The issue, he says, is that ground penetrating radar has limitations: you get a better resolution with a high-frequency signal, "but the higher the frequency, the shallower the penetration possible." A software database system on previous radar scans conducted for different rebar types and conditions could provide more accurate interpretation of the data from what is being examined, "despite limited information on the actual case or sample. The computer screen shows us a pattern of different colours and geometric forms that requires experience in order to interpret. An industry effort to augment accurate interpretation of radar signals would be helpful," Heere says. An overall trend of more high-rise construction imposes a rigorous construction schedule on concrete contractors. Floor flatness measurements taken immediately after pouring may change as the floor slab cures, resulting in delays or costly floor preparation before the installation of other flooring products. "Often concrete is not drying fast enough on the floor slab and that slows construction," says Dave Nicholson, international technical manager at Maxxon. Maxxon's solution goes by the acronym SMART, which stands for slab moisture and resurfacing technology. It combines Maxxon MVP, an epoxy-based moisture vapour protection product with Level-Right self-levelling underlayments. To help Concrete + Redstone project: a total precast supported-living building for seniors.