Roads & Paving
Quality road repair in record time
An experienced roadbuilder in Victoria, B.C.
November 4, 2008 By Andy Bateman
Island Asphalt is a
well-established roadbuilder on Vancouver Island and part of OK
Industries Ltd. Brad Hoey, Island Asphalt’s general superintendent,
explains that the company was recently awarded a contract to repair a
section of Devonshire Road in Esquimalt, some two kilometres west of
|The four-way bucket on this Bobcat S250 aided high speed clean up of milled material.|
An experienced roadbuilder in Victoria, B.C. completes quality road rehabilitation in less than twelve hours.
Island Asphalt is a well-established roadbuilder on Vancouver Island and part of OK Industries Ltd. Brad Hoey, Island Asphalt’s general superintendent,
explains that the company was recently awarded a contract to repair a section of Devonshire Road in Esquimalt, some two kilometres west of downtown Victoria. Work included the milling and removal of existing asphalt, fine grading and the paving of a new surface asphalt lift. The work order stipulated milling to a depth of 60 mm to remove 50 mm of existing asphalt plus a further 10 mm to allow for fine grading and base compaction before the placement of 50 mm of new asphalt. The contract covered a 245 m stretch of one lane of the 10 m wide two-lane suburban road along the frontage of a new commercial development. For both the travelling public and the contractor, the completion of this job in a single day had a number of advantages. Rapid completion minimised traffic delays and access issues for the public, while simplifying job logistics such as overnight traffic control and site security for the contractor.
Work kicked off shortly after 7 a.m. on a sunny morning with the first pass by a Caterpillar PM465 cold planer. Shortly after that, it became clear that the existing asphalt near the road centre was thicker than at the road edge, possibly due to a road overlay and widening completed many years ago. As those involved in road rehabilitation already know, it is often difficult to establish the exact make up of an old road which may have seen repairs, overlays or widening a number of times. In this case, the increased asphalt thickness meant milling to a greater depth than originally planned and an increase in granular material quantity to bring the road base back up to grade prior to paving. This minor hitch apart, work proceeded smoothly.
|One of Island Asphalt truck fleet feeds a Caterpillar AP 1050B paver.|
Granular base placement and grading began at 9 a.m. with the arrival of the first loads of recycled concrete granular base. A Caterpillar 140G grader began the levelling and grading process, working in tandem with a Volvo DD-24 compactor helping to set the compacted base level along the curb edge. Compaction of the remaining base was completed by a new Ammann AV95-2K articulated combination roller. Hot mix asphalt paving began at one o’clock, with the 12.5 mm surface mix, known locally as MMCD upper course mix #2,
supplied from Island Asphalt’s hot mix plant located on the east side of Victoria’s inner harbour. On site, asphalt paving was completed
by a Caterpillar AP1050B paver equipped with Topcon grade control and a Carlson EZ Screed IV. The Ammann compactor went into action again to provide breakdown compaction of the asphalt, followed by a Hamm GR5 pneumatic roller in the secondary position and the Volvo unit to finish the mat. By 2.30 p.m., the paving job was well advanced, and the whole job was wrapped up within ten hours by 5 p.m.
Superintendent Ross Kennedy emphasises that accurate material placement and attention to detail are essential, regardless of job size and any time pressure. As a former grader operator, Kennedy is well tuned to such issues and gives an example to make the point. While placing and grading base material on this job, the objective was to finish the compacted base surface 45 mm below the level of the curb. Had the finished base level been left 50 mm or more below the curb instead, the surface of the finished mat would be below the curb instead of above it. So what difference does a mere 5 mm make? In practice, that 5 mm can significantly affect road durability. If the mat surface is slightly proud of the curb, water can drain freely off the asphalt and into the storm water system. Leave the asphalt low on the other hand, and water running off the asphalt can get caught in the longitudinal joint between the mat and the curb. Over time, trapped water may seep down through the joint into the underlying base material and reduce the service life of the pavement through water or frost damage.
Pavement durability aside, there is also the cost aspect of accurate material placement, given the current high cost of materials. As an illustration, consider the costs involved in paving and area just 50 m by 20 m. If the compacted asphalt thickness over that 1000 m2 is 50 mm, then 50 m3 (125 tonnes) of hot mix will be required to do the job. Increase the asphalt thickness by just 1mm and an extra 1 m3, about 2.4 tonnes, of additional hot mix is required. Even based on a conservative asphalt cement price of $700/tonne, the in place cost of that single extra 1 m3 including material, haulage and laydown cost is about $375.00/m³ ($150.00/tonne.) Take a larger area, current A/C prices and thicker asphalt and the numbers quickly get bigger.
Staying on money, some might still be wondering why half a road would be repaired. The answer lies in the funding of the work order. In this particular case, the developer of the new commercial property provided some $110,000 for a new section of sidewalk, new services and road repairs to the centre line, since that was the deemed impact area of the development on the existing infrastructure. Elsewhere, the same concept is being applied on an increasing scale, with the impact of larger developments such as condominiums being assessed for much wider infrastructure impacts and thus becoming part of the overall municipal planning process. In addition to Island Asphalt, other companies in the OK Industries Ltd. group include Duncan Paving, Haylock Bros. Paving, Tayco Paving, OK Paving, Island Crushing and Northwest Sealcoating. The group operates seven stationary asphalt plants on Vancouver Island, together with a portable asphalt plant and three portable aggregate crushing plants.
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