January 3, 2012

Hot on hot paving not so hot yet in Ontario but outlook is promising

DAN O’REILLY

correspondent

Hot on hot paving may be on the brink of a major breakthrough in this province judging by the comments from a joint presentation at the recent Ontario Hot Mix Producers Association’s annual conference.

With this relatively new technique, one piece of equipment places two layers of hot mix asphalt in a single process. First the binder course is applied and then the wearing course.

Hot on hot paving had its first commercial application in North America last September near Midland along a 2.7- kilometre stretch of Highway 12 which is comprised of both four- and two-lane portions. The trial section is just one part of an overall 6.7-kilometre reconstruction of the highway from Highway 93 to Talbot Road.

That section was selected by the Ministry of Transportation after its engineers investigated the technology and met with Dynapac, the German manufacturer of one of the two pieces of equipment available for this type of paving.

The findings of the three-week experiment are still being assessed by the Ministry and the general contractor, K. J. Beamish Construction Co. Ltd.

But the lessons learned and the possibilities of accelerating road construction with hot on hot paving looks promising, according to the presenters: Fernando Magisano, vice-president of technical services for Beamish and Chris Raymond, head of the Ministry’s bituminous section.

At the heart of the operation is the Compactasphalt paver which is basically two pavers in one, said Magisano. It consists of a bottom paver which lays the bottom lift and a module that applies the top layer. After a feeder loads the 31-tonne hoper on the bottom layer, it shifts position and loads the surface mix into the 17-tonne hopper on the paver module.

Earlier this year Beamish sent a service technician and its paving foreman to Germany to obtain first hand knowledge. In August a machine was shipped from Canada and Dynapac sent a five-member technical team to assemble the equipment and train the Beamish paving crew.

A very tight schedule did not leave a lot of time for that training. However, as the crew became more comfortable with the machine, “the Dynapac people were doing less and our people were doing more.”

There were more than a few challenges such as a requirement that most of the paving had to be done at night to limit traffic congestion, plus the limitations of the paving equipment on short radius ramps, tapers and intersections, he said.

As well, there were concerns about the capacity of the granular sub-grade to support the weight of the machines and safety concerns about the 140-mm drop at the edge of pavement which prevented the flow of traffic on and off partially paved lanes.

“A lot of things had to be addressed very quickly,” said Magisano, in reference to a number of negotiated changes with the Ministry, such as extending lane restrictions hours to avoid concerns about the 140-mm drop.

Not everything worked perfectly but core samples indicated that good compaction was achieved, he said.

As a result of the experiment, the Ministry believes that hot on hot paving is more suited for greenfield construction, such as the Highway 407 East Extension, said Raymond.

“It may not be ideal for (Highway) 400 series night closures.”

It has also concluded that the technology isn’t practical for intersections, ramps, tapers or short widenings, he added.

The Ministry will continue to evaluate findings from the trial project as it pursues future opportunities with hot on hot technology, said Raymond.

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