In what is being described as a milestone for highway construction in Ontario, the 417 contract was awarded not only on the initial construction costs, but also on the long-term cost of maintaining the roadway. The bidding process for 417 differed from conventional jobs in that contractors had the option of submitting bids in either concrete or asphalt pavement, in accordance with the stipulated pavement designs for each material.  The Life Cycle Costing (LCC) model is based on a 50-year life cycle of the pavement and takes into account all the rehabilitation and repair costs associated with the pavement over that time. Future repair and rehabilitation costs during its life span are all expressed in present day dollars to allow direct comparison between concrete and asphalt construction. Under the LCC model, bids are adjusted by a concrete or asphalt adjustment factor, as appropriate, which is added to the total tender to arrive at a total adjusted tender price. In the case of the 417  contract, the concrete adjustment factor was $433,321 less than the asphalt adjustment factor, reflecting the lower present day value of its future costs compared to the asphalt equivalent. The discount rate of 7 per cent used by the MTO for the 417 contract was provided by the Ontario Ministry of Finance and will vary according to economic conditions.

The LCC model used for 417 does not mean that all the province’s future pavements will be constructed in concrete, as there is a minimum practical thickness at which concrete can be laid, and in low and medium volume applications concrete may not be competitive with asphalt pavement designs.

For advocates of concrete road construction such as Dufferin Construction’s parent company St. Lawrence Cement, this successful bid on 417 is the culmination of six years of work by the company, the Cement Association of Canada and the Ready Mixed Concrete Association of Canada. Lloyd Ferguson, general manager of Dufferin Construction, recognizes the importance of this pilot LCC project, "We are employing both our best people and machinery on the job.  District manager Michel Rodrigue and project superintendent Cory Greer of our Ottawa office are leading the team which is utilising state-of-the-art equipment such as our Guntert & Zimmerman S1500 slipform concrete paver. This machine is capable of paving two lanes and the shoulder in one  pass and also incorporates a dowel bar inserter." The S1500 was relocated from Toronto where it was working on the expansion of Pearson International Airport. Based on the success of their S1500, Dufferin purchased a new S850 mid-size slipform paver with a dowel bar inserter for use at the airport project.

According to Ferguson, the 417 contract is an effective demonstration of the use of concrete in road construction. "Any roadbuilding job has three key elements – thickness, strength and ride quality, and we know we can deliver on all three." On the ride quality aspect of the 417 job, he notes that Dufferin’s paving crew is producing a pavement with smoothness readings of 90 mm or less per kilometre, well below the MTO requirements of 240 mm/km.

Spearheaded by the company’s new computer-controlled concrete paver, slipforming operations are progressing at the rate of 800 m of roadway a day. Dufferin’s MTO Contract 00-0025 includes full pavement reconstruction of a 36.6 km stretch of the east-bound lanes of Highway 417, including grading, drainage, granular base, concrete pavement, structural and electrical work.  The job has been further divided into three smaller sections – the western and eastern sections, totalling some 25 km in length, will be completed this year, while the remaining 11.6 km central section will be completed next summer. This sectional phasing is designed to reduce traffic congestion by giving vehicles the opportunity to disperse and overtake slow moving vehicles in the central section. The western section extends 14.6 km from Dunvegan Road (6.8 km east of interchange #51) to Highway 34 and the 10.4 km eastern section runs between Barb Road and Highway 17. On both sections, eastbound traffic has been diverted to the westbound side, reducing traffic flow from four lanes to two.

In cross section, the new pavement consists of a 150 mm bed of granular B base material followed by 150 mm of granular O and the 200 mm thick exposed concrete slab.  The granular B incorporates recycled road base that has been crushed on site to specification, while the open graded granular O provides effective drainage, in conjunction with some 54 km of 102 mm diameter perforated pipe laid on each side of the concrete pavement.

Project superintendent Cory Greer explains that a CMI TR-450B trimmer leads off the roadway rebuilding process by trimming and levelling the base material to correct line and level. The TR-450B is followed by Dufferin’s Guntert & Zimmerman S1500 slipform paver, a multi-function unit that screeds, forms and consolidates the concrete, inserts the dowel bars in the pavement’s transverse joints and provides initial surface finishing.

The G & Z S1500 lays the 8.0 m wide concrete slab in a single pass at the required 2 per cent slope (cross fall), to form the two 3.75 m lanes of the mainline pavement as   well as a 0.5 m wide concrete strip. This strip provides a high strength edge to the right hand gravel shoulder while the 1.0 m wide left hand shoulder will be surfaced with hot mix asphalt at a later date.

During the paving operation, concrete is dumped in front of the advancing paver by a fleet of open tandem trucks. Here, it is distributed evenly across the base material by the S1500’s frontal spreader and then formed into a continuous slab by its vibrating screed.  In back of the screed, the on-board dowel bar system inserts a set of horizontal dowel bars directly into the surface of the fresh concrete from above, repeating the process every 4.6 metres at each transverse joint. The bars are positioned in a random sequence across the width of the slab according to one of four preset patterns in the unit’s onboard computer.  Each joint contains between 17 and 20 of the 32 mm diameter by 457 mm long bars, set at 300 mm centres.

Following insertion, the position of each joint is marked for relief joint cutting. The surface concrete then receives a multi-stage finishing process that includes both mechanical and hand finishing. Behind the dowel bar inserter, a sheet of wet burlap and the S1500’s rotating bull float provide initial smoothing, followed by Dufferin’s crew who hand finish both the surface and the edges of the slab.

Working behind the slipform paver, a travelling Bidwell workbench straddles the concrete. This machine allows the crew to access the central area of the slab and complete any necessary final finishing. A second sheet of burlap, dragged behind the work-bench, then adds longitudinal texture to the concrete surface.

The last major piece of equipment in the paving train is the dual purpose Guntert & Zimmerman TC 850 texture cure machine.  During its first pass over the concrete, its tines cut fine transverse grooves in the fresh concrete surface in order to provide optimum skid resistance. The TC 850 then seals the surface with a curing compound. On this job, two coats of AHT cure Type II Class B white curing compound were being applied.   Some five to six hours after paving, a relief cut is made at each transverse joint, together with a central longitudinal relief cut. The joint operation is completed following a curing period of 27 days, when each joint is groove cut to 19 mm x 19 mm and filled with Ultraseal # 190 joint compound.

As a precaution, Dufferin is keeping a Gomaco PS 60 concrete placer/spreader on standby in case the stability of the granular becomes a problem in wet weather. In this event, the placer/spreader operates ahead of the G &Z S1500 paver, spreading the concrete in front of the paver and ensuring that it is evenly placed on grade in readiness for the paver.

The same portable ready mix batch plant that supplied the central section of Toronto’s Highway 407 from Oakville to Markham is producing concrete for the 417 job. During Aggregates & Roadbuilding’s visit, the Johnson-Ross Unirover 1048 portable plant was averaging about 1000 m 3 /day production and loading trucks with 6.5 m 3 batches at three minute intervals. The mix is batched to a target slump of 70 mm and its design includes 320 kg/m 3 of Type 10 cement, 4520 kg of sand, 4920 kg of 19 mm coarse aggregate and 3260 kg of 38 mm aggregate, as well as Euclid’s Eucon DX water reducer and Airex L air entraining agent. A fleet of 11 trucks hauled the concrete about 6 km to the paver and Greer reports that these tandem units deliver consistent mix, while providing fast unloading times and relatively low delivery costs.