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Canada's “Rock to Road”
Magazine
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Trans-Canada Highway upgrade targets water removal Valued at nearly $24 million, Ontario Ministry of Transportation (MTO) contract 2000-0218 is a road rehabilitation contract on the Trans-Canada Highway (Highway 17) between Sturgeon Falls and North Bay. The job was awarded to the Northern Ontario Division of Lafarge Construction Material’s Eastern Region last fall and includes asphalt milling, grading, drainage, granular base and hot mix paving on a 15.3 km section from 3 km east of Coursol Road to 100 m west of Laronde Creek. The highway is being upgraded at the same time by the relocation of a main side road intersection, the addition of three passing lanes, culvert replacement and new illumination. Jeff Hueston, Area Construction Engineer in the MTO’s North Bay office, reports that the main objective of the work is to provide lateral drainage for the road’s granular base layers and in particular its subbase layer. The original two-lane pavement was constructed in concrete with standard 3.65 m lane widths, on a granular subbase and with granular shoulders. Later, the road was rehabilitated by the addition of a further lift of granular base and hot mix asphalt surfacing on top of the existing concrete. However, the lateral drainage of the granular subbase layer under the concrete has always been poor, due to its incompatibility with the earth fill under the shoulders. As a result, the subbase becomes saturated, particularly in the spring when swampy conditions exist in the low-lying areas on either side of the highway. In this condition, the strength of the subbase is reduced and it provides less support for the concrete above. On the plus side, core test results confirm that the concrete is in good condition and does not require any treatment.
The shoulder and fill material on both sides of the original concrete pavement is being replaced with new granular material to facilitate lateral drainage. To correct the drainage situation, the shoulder and fill material on both sides of the original concrete pavement is being excavated and replaced with deep sections of new granular material, thereby allowing water to flow laterally out of the daylighted subbase. In addition, the overall grade (elevation) of the pavement is being raised by a further granular lift together with new hot mix asphalt. Drainage work begins with the excavation of the old shoulder material to a depth of 1.8 m below the existing surface asphalt level. The material is removed in wedge–shaped sections, typically 8-9 m wide on the north side of the pavement and 4-5 m wide on the south side. This process will generate a total of 540 000 m 3 of granular and earth fill that has been popular with local landowners as clean fill for land reclamation. After checking for grade, the excavation is backfilled with 100 per cent crushed Granular B from Lafarge’s Bourassa quarry, laid in three successive lifts of 700, 600 and 500 mm. Typical rolling patterns for the granular backfill are two passes for the first lift and six passes for the second lift and top lifts. Tera North Construction of Sudbury, subcontracted by Lafarge to complete the earth excavation and granular B backfill, has utilised three Caterpillar 330B and two 322 excavators, Caterpillar D5M XL and D5C XL dozers, a Caterpillar 416C rubber tired backhoe and three Bomag BW 213 D-3 compactors for these operations.
Water being added to the granular subbase material to aid in compaction. In the paved central section, subcontractor Rotomill Services of Brampton has utilised a CMI PR 800-7 pavement profiler to mill about 200 mm of existing surface asphalt and reveal the upper granular base layer. The generated RAP material is taken back to the quarry for blending with the quarried granular A base. Once the granular B backfill and milling operations are complete, the whole pavement receives a new lift of granular A across the full width of both the central section and the shoulders. This material can, by specification, contain up to 30 per cent RAP and is laid at a minimum thickness of 300 mm depending on location. Equipment utilised by Lafarge for material handling, grading and compaction includes three Caterpillar wheeled loaders (two 980G’s and a 966F), Champion 740 (owner operated) and Caterpillar 14H graders and two SuperPac 8410 single-drum compactors. Work on the central section will be completed by the paving of three lifts of hot mix asphalt totalling 130 mm, laid at a 2 per cent slope. An estimated total of 64 048 tonnes of hot mix, includes 47 770 tonnes of Heavy Duty Binder Course (HDBC) laid in two lifts of 50 mm and 40 mm as well as 16 278 tonnes of HL4 modified surface asphalt, laid in a single 40 mm lift. Lafarge will be supplying both the asphalt and concrete requirements for the job from its plants in North Bay. After paving, the shoulders will be surfaced with a final 130 mm lift of granular A mix containing 50 per cent RAP and laid at a 6 percent slope. By the job’s completion, all of the estimated 273 000 m 2 of RAP generated by the milling operation will haveall been reused in the two recycle granular A mixes.
Granular A, containing up to 30 per cent RAP, is compacted by a SuperPac 8410 single-drum roller. Lafarge contracts manager Tom Mills explains that the job will extend into next year’s construction season. He adds that no detours are allowed to be operational at the end of this year’s construction season, and the contractor is required to tie a two-lane section of the new construction into an existing two-lane section. With that in mind, the project has been divided into manageable work areas to maintain flow for the construction equipment while giving due consideration for the travelling public during construction. At season’s end, a safe transition with the existing highway will be made. Excavation, backfill and paving are staged. In stage one, part of the south shoulder was excavated, backfilled and temporarily paved to maintain two lanes of traffic. With traffic detoured on the south side, the main excavation on the north side will completed and paved. Traffic will then be switched to the completed north side allowing completion of the excavation and paving of the south side. For the final step, traffic will be directed back onto the final alignment. In addition to maintaining two lanes at all times, contract conditions require that all excavated areas are backfilled each night. Normal hours of work are limited from 7 am to 7 pm, with no mainline work after 3 pm on Friday afternoons. In addition, no work is allowed on statutory holidays or weekends. Daily production rates on this job have been impressive. This year’s record for granular shipments from the Bourassa quarry peaked at 19 000 tonnes, all weighed across a single Mettler-Toledo 18.3 m long, 90-tonne capacity scale, while the daily average of about 15,000 tonnes, includes some 12,000 tonnes of granular B and 3,000 tonnes of granular A. A second scale, a 15.3 m long, 80-tonne capacity unit built by Canadian Scale, has been added to deal with the truck volume. With a maximum haul of about 8 km in each direction, these production rates have been maintained with between 20 and 25 hired trucks. Triaxle trucks, with their ability to reverse into relatively tight spots have been utilised to haul the granular B, while the granular A has been shipped using a fleet of five belly dump trailers. Meanwhile, an additional fleet of up to 20 tandem tracks have been hauling excavated material to the designated fill sites. Malcolm Croskery is Lafarge’s site superintendent on the Highway 17 project.
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