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Media / Application stories / Paving Canadian highways looks promising with Compactasphalt®

Paving Canadian highways looks promising with Compactasphalt®


2013-07-09

In 2012, a new type of high-performance paver, Compactasphalt® from Dynapac, completed the first Canadian trial on Highway 12 near Midland, Ontario using latest dual layer paving technologies.

A relatively new technique, hot on hot paving is applied by a single piece of equipment laying two lifts of asphalt virtually simultaneously.

“Any process that does two things at once is bound to be more efficient”, says Erik Thorsrud, General Manager, Atlas Copco Construction Equipment Canada, “but there is more to compact asphalt paving than that, you also get a stronger more durable road.”

Dual layer paving systems, developed in Europe since the early 1990s, now offer hot on hot paving making this new technology the future of the paving industry.  A single piece of equipment places two lifts of asphalt in one pass; first the binder course followed almost immediately by the wearing course. Currently, only two manufacturers offer hot on hot pavers, Vögele with its InLine Pave® and Dynapac with its Compactasphalt® paver. For the Midland project, the Atlas Copco/Dynapac system was selected. As explained by Bill Wilcox, Business Line Manager- Heavy Equipment at Atlas Copco Construction Equipment Canada, the paving train consists of five pieces of equipment.  At the heart of the process is the Compactasphalt® paver, which is essentially two pavers in one. The bottom paver, which lays the bottom lift, and the module that rides on the bottom paver and applies the top layer of asphalt. (The module can be removed and the paver used for conventional paving as well). A feeder loads the 31-ton hopper on the bottom paver with the binder mix and then shifts position and loads surface mix into the 17-ton hopper on the paver module. The feeder takes just over a second to load a ton of hot mix. The paver places the asphalt with the two hoppers feeding two synchronized screeds. The high compaction screed compacts the binder course, after which the second screed compacts the surface course. A wide low pounds per linear inch static roller compacts the two lifts. After the mixes have been stabilized, standard rollers provide the final compaction. The hot on hot paver is expected to cost about 40 percent more than conventional paving equipment but the combination of increased lifetime and enormous savings on top layer material makes Compactasphalt® a real winner.

Quicker and Better

There are obvious advantages to using a dual paving system, not the least of which is the improvement in construction efficiency. Paving is expected to be about 35 percent faster, Wilcox estimates, and only one paving crew is needed. The dual layer of asphalt retains heat better than conventional paving and as a result contractors can pave at lower ambient temperatures extending the paving season. There is also less traffic disruption since only one lane needs to be closed at a time (a notable benefit for night paving on the 400 series of highways). But it is the need for more durable roads that may prove to be the driving force behind hot on hot paving. The thickness of the wearing course is defined by the size of the aggregate. A surface lift of Superpave 12.5 is typically three times the thickness of the nominal aggregate size, resulting in a lift of 40 millimetres. With conventional paving, the wearing course is laid on a compacted binder course and needs thickness to retain heat for compaction. With hot on hot paving, the binder course is both hotter and softer. “Since the bottom course is softer and more flexible, you are not crushing and driving the stone in the top layer,” notes Thorsrud. “You can use a thinner top lift, which saves material costs, while at the same time getting much better interlocking between the two layers without resorting to a tack coat. This is a better road building method because you get a solid road with a much longer life. Using conventional technology, a properly paved wearing course lasts 10 to 15 years, while the binder course lasts 15 to 25 years. With hot on hot paving, the wearing course will last as long as the binder layer.”

Dynapac introduced its first Compactasphalt® train in 2004 and while this type of paving is only now making its way to North America, it has been used to pave sections of the German autobahn between Bremen and Hamburg, which features some of the highest volumes of heavy truck traffic anywhere in Europe. A dual layer pavement was tested at the National Center for Asphalt Technology test facility in Alabama over a thirty-month period and despite being subjected to 10 million axle loads, the paved surface showed no signs of deformation.

Later in 2012, Atlas Copco along with a leading Ontario contractor used Compactasphalt® to pave the Peace Bridge Toll Area in Fort Erie, Ontario.  The project lasted 14 days and was completed quickly.  This was another unique application for Compactasphalt®.  The system showed its versatility paving “tapered lanes” starting from 8 lanes to 2 lanes in width in both directions. The Atlas Copco/Dynapac system laid approximately 48,000 tons of asphalt, in 2 lifts over the 14 day period. The Ministry of Transportation in Ontario and the contractor were very pleased with the quality of the paving and the performance of the system.

These new technologies will drive Atlas Copco growth in Road Construction into the future.

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Atlas Copco is an industrial group with world-leading positions in compressors, expanders and air treatment systems, construction and mining equipment, power tools and assembly systems. With innovative products and services, Atlas Copco delivers solutions for sustainable productivity. The company was founded in 1873, is based in Stockholm, Sweden, and has a global reach spanning more than 170 countries. In 2012, Atlas Copco had 39 800 employees and revenues of BSEK 90.5 (BEUR 10.5).

Atlas Copco’s Construction Technique business area provides construction and demolition tools, portable compressors, pumps and generators, lighting towers, and compaction and paving equipment. It offers service through a global network. Construction Technique innovates for sustainable productivity in infrastructure, civil works and road construction projects. Principal product development and manufacturing units are located in Belgium, Germany, Sweden, China and Brazil.

Road Construction Equipment is part of the Construction Technique business area. The division is a leader in asphalt, soil and concrete applications, committed to customer performance worldwide. Products and solutions are marketed under the Dynapac and complementary brands. Headquartered in Wardenburg, Germany, the division has production facilities in Europe, USA, South America, and Asia.