Canada's “Rock to Road” Magazine

November-December 2003 Issue

• New equipment promises high productivity, low cost for
  West Coast aggregate producer
• Superpave aggregates go the distance
• Concrete road paver heads east for big job
• Expanded asphalt with HMA overlay protects road assets for Ontario city
• Roadbuilding job compares in-place asphalt recycling techniques

For a copy of the issue that contains these articles with colour photos, click here.

New equipment promises high productivity, low cost for West Coast aggregate producer

By Andy Bateman, Engineering Editor

Mobile equipment changes at a major B.C. aggregate producer's operations promise to diliver high productivity at low cost.

    Vancouver-based Construction Aggregates Ltd. (CAL) recently took delivery of seven new pieces of equipment including four wheel loaders, two ADT trucks, and an excavator for their Lower Mainland and Sechelt B.C. operations. Sechelt will be a familiar name to Aggregates & Roadbuilding's readers, having occupied the top spot in our annual survey of the country's Top 20 Sand & Gravel operations for a number of years, reporting over 3 million tonnes of production for 2002.
     At Sechelt, mine manager Gordon Doerksen reports that two Komatsu WA700-3 wheel loaders and a Komatsu PC1250LC-7 excavator went into service this year. The first WA700 arrived this spring and was joined in September by the second WA700 and the PC1250. Working exclusively at Sechelt, all three units have manufacturer's extended warranties as well as "not to exceed" full maintenance packages. The PC1250's main duty is the excavation of overburden and sand and gravel, where it is teamed with Caterpillar 773 and Terex TR-70 haul trucks. The WA700s are engaged in stockpile pushing and pulling as well as material extraction.
     Key factors cited by Doerksen in the purchase of these new machines include lowest long-term cost per tonne, the manufacturer's commitment for a full-time site service person, a machine availability guarantee and favourable reports from existing owners. Doerksen also underscores the importance of operator input, noting that two operators completed trials with these machines before purchase, including a comparative performance test against a shortlist of competitor's machines. With its expected life of 6 years, Doerksen reports that the PC1250 excavator is delivering a 50 per cent increase in capacity from 4 to a potential 6 million tonnes/year. In terms of average production rate, the new excavator has reduced truck loading time by up to 33 per cent, from 1.5 minutes to as low as 1 minute.
     At the company's Port Coquitlam quarry operation near Vancouver, two Komatsu HM300-1 articulated dump trucks (ADT's) went into service in mid-August of this year while two Komatsu WA500-3 wheel loaders went to work at CAL's North Vancouver and Langley depots. Dennis Baker, CAL's operations manager for the Lower Mainland & Gilley's Quarry, explains that both trucks and one of the loaders are on rental purchase whereas the second loader has been purchased. These are all stock units, with the trucks typically carrying feed to the quarry's rip-rap plant, and also loading 4500-tonne capacity barges when required. Duties for the loaders include truck loadout and barge unloading. Baker reports that the units are delivering excellent performance, are operator friendly and have increased overall capacity by about 20 per cent, adding that it is too early to comment on their operating costs.
     Manufacturer's specification data on these new machines indicates that the PC1250LC-7 excavator has an operating weight of 113.2 tonnes and a rated bucket capacity range of 3.4 m3 to 5.2 m3. This excavator is one of the Komatsu's Dash-7 Series machines which are claimed to offer high production and low fuel consumption. These models are equipped with three working modes - A, E and B mode for active, economy and breaker operation, respectively. CAL's particular machine is fitted with a number of options, including extra lights, autolube systems, a modified windshield and a fire suppression system.
     Data on the WA700-3 wheel loaders indicates a rated bucket capacity, when equipped with a general purpose bucket (straight edge) without tip teeth, of 9.4 m3 heaped and 8.2 m3 struck, delivering a breakout force of 62 400 kg. For the WA500-3, rated bucket capacity, fitted with a general purpose bucket with bolt on cutting edge, without tip teeth, is 5.0 m3 heaped and 4.3 m3 struck, delivering a breakout force of 23 700 kg.
     Turning to the HM300-1 ADTs, these machines have a maximum rated payload of 27.3 tonnes and a heaped body capacity of 16.6 m3. High productivity is claimed from performance numbers such as a maximum travel speed of 59.0 kph (36.7 mph) and a minimum turning radius of 7.96 m.
     Overall, the new machines are meeting both managers' expectations to date. Aggregates and Roadbuilding will report their views on the machines longer term performance in a future edition. Construction Aggregates Ltd. is part of the North American Lehigh Group and worldwide Heidelberg Cement group.

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Superpave aggregates go the distance

By Andy Bateman, Engineering Editor

With the increasing use of Superpave asphalt mixes and tight supply, quality aggregates are travelling further than ever before in southern Ontario. This article describes how one custom crushing contractor met specifications for a Superpave surface mix aggregate used in several distant roadbuilding projects.

    Both granite and sand and gravel are extracted from the Aspdin Rd. operation of W. Robert Hutcheson Sand & Gravel Ltd. near Huntsville, Ont. Crushing contractor J.G. Stewart Construction Ltd. has been there three years a row and focussed this year on maximizing production of HL1 sized (13.2 mm x 4.75 mm) Superpave granite aggregate for Dufferin Aggregates. Dufferin has been successfully marketing HL1 stone and Dense Friction Course (DFC) aggregates south of Barrie through a distribution arrangement with Hutcheson, with the result that these products are being trucked as far the Niagara Region, nearly 400 km from the quarry.
     Aggregate processing began at the quarry's rock face, where two of Stewart's wheel loaders, Caterpillar 988B and 988F models, hauled shot rock from the 18.3 m high granite face at a rate of 360 tonnes/h to the primary, a 37x49 Nordberg C125 jaw crusher. The jaw reduced the 600 mm minus feed to 150 mm minus and was fitted with a BTI TB-725X breaker to deal with any oversize. From there, two 914 mm x 30.5 m long Riverwood transfer conveyors and a 914 mm x 76.25 m Riverwood field conveyor carried material to the secondary plant, discharging into a 30-tonne capacity metering bin. The bin regulated flow onto a 6x16 Cedarapids ElJay double-deck screen fitted with 32 mm and 22 mm screen cloths. Here, 150 mm x 32 mm oversize material continued forward for further processing, while 32 mm x 22 mm clear drainage stone and Granular A base sizes were drawn off and stockpiled. The oversize first passed through a Cedarapids 1372 mm (54-in) Rollercone, set at a closed side setting (CSS) of 38 mm before being conveyed to a 8x20 Cedarapids triple-deck inclined screen fitted with 32 mm (top), 15.9 mm and14.3 mm (middle) and 6.3 mm (bottom) screen cloths. All 14.3 mm plus material retained on the screen's top and middle decks was conveyed to a Nordberg HP 400 cone for further reduction, while HL1 product continued forward and 6.3 mm minus screenings were stockpiled separately. Plant foreman Alvin Lamb puts the plant total throughput rate with this set up at 360 tonnes/h, an impressive number bearing in mind that all of the granite feed was reduced to 19 mm or smaller sizes. Out of this total, Lamb estimated the product split at 35 per cent HL1 together with 35 per cent screenings, 25 per cent granular A and 5 per cent drainage stone.
     In many set ups, the secondary screen would mark the end of the material processing. Here however, Stewart refined the process by a number of additional steps, including a finishing screen to remove residual fines from the HL1.
     The 5x16 Dillon double-deck finishing screen was fitted with 14.3 mm and 6.3 mm screen cloths, with the 14.3 mm cloths dispersing the material flow and the 6.3 mm cloths completing the fines separation. As an added refinement, HL1 product from the Dillon screen was stockpiled by a Thor 914 mm x 41.9 m programmable stacker to minimise segregation. Finally, 6.3 mm minus screenings from this screen (and also occasionally from the Cedarapids screen) were subdivided into 6.3 mm by 3.2 mm chip and 3.2 mm minus fractions so that some of the chip fraction could be separately shipped and metered into Superpave asphalt mixes.
    According to Stewart president John Stewart, this set up is just one example of company's track record on Superpave aggregate production. "This year alone, we have successfully met Superpave specifications in a number of locations, utilising both hard rock and gravel sources. We have found that some initial experimentation with our portable spread set ups, followed by good production practice has normally delivered the required result."

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Concrete road paver heads east for big job

By Andy Bateman, Engineering Editor

   Making its first appearance in the Maritimes, a concrete road paver has played a key role in the upgrading of Nova Scotia's Highway 101. Andy Bateman reports...

    Concrete won out over asphalt for a major highway paving project in Nova Scotia based on life cycle costing by the winning bidder. Project number 2003-030 was awarded by the Nova Scotia Department of Transport and Public Works (TPW) for one section of Highway 101 in Hants County between Halifax and the Annapolis Valley. Extending 10.9 km, work involved the construction of two new lanes and shoulders for eastbound traffic, together with the removal of existing climbing lanes on the westbound lanes. Bidders had the option of submitting bids based on Alternate 1, Gravelling and Portland Cement Concrete Paving or Alternate 2, Gravelling and Asphalt Concrete. The aggregate amounts submitted for the asphalt alternate were then increased by $1,500,000 in accordance with the project tender documents.
     St. Lawrence Cement Inc. submitted the winning bid of $5, 911,460 utilising the concrete alternate. Project manager Jean-François Côté explains that the ability of the company's concrete paver to complete the paving operation in a single pass was critical to the bid's aggressive 3-week paving schedule. Côté adds that the bid package also drew extensively on the area's workforce with local contractor Alva Construction Ltd., for instance, responsible for all earthmoving, base material crushing, placement and fine grading as well as the installation of nearly 6 km of guardrail.
     In cross section, the pavement foundation utilizes two coarse graded base materials to both support the concrete and facilitate drainage; gravel Type 2 (102 mm minus) sub-base material and a 100 mm lift of Type 1 (20 mm minus) granular base material for Portland Cement concrete. The concrete pavement itself is 10.6 m wide, consisting of two lanes each 3.7 m wide, together with a 2.0 m wide tied concrete shoulder to the right lane and a 1.2 m wide integral shoulder for the left lane. At 240 mm, the concrete thickness under the right lane is 20 mm more than the left lane in recognition of the right lane's heavier truck loading.
     Base aggregate tender quantities included 25 000 tonnes of Type 2 granular sub-base and 40 000 tonnes of Type 1 granular base, as well as 25 000 tonnes of gravel type 1S shoulder material adjacent to the concrete. The pavement contains some 27 000 m3 of concrete, based on its surface area of 116 000 m2 and 230 mm average thickness.
     Preparatory work included the fine grading of the base material to ensure a level surface for concrete paving operations. Initially completed some 3 km ahead of the paver, the fine grading was later reduced to about 500 m ahead in steady running conditions to provide a smooth surface for paving. As a further precaution, one of the compactors was stationed ahead of the paving train to iron out any small grooves left by concrete delivery truck.
     At the heart of the concrete paving operation was Dufferin Construction's Guntert & Zimmerman S-1500 paver. This multi-function unit formed and consolidated the concrete to the required slope, inserted dowel bars for the pavement's transverse joints and provided initial surface finishing. During paving operations, concrete was dumped in front of the S-1500 by a fleet of up to 15 open tandem trucks and distributed evenly across the base material by the paver's frontal spreader. The concrete was then formed into a continuous slab by the paver's vibrating screed. Behind the screed, the on-board dowel bar system then inserted 24 greased dowel bars horizontally into the surface of the fresh concrete from above, repeating the process every 5 m at each transverse joint. Following insertion, the position of each joint was marked for later joint cutting. The surface concrete then received a multi-stage finishing process that included both mechanical and hand finishing. Behind the dowel bar inserter, a sheet of wet burlap and the 1500's rotating bull float provide initial smoothing, followed by Dufferin's crew who hand finished both the surface and the edges of the slab. Towed some distance behind the paver, a travelling Bidwell workbench straddled the concrete, allowing the crew to access the central area of the slab to complete any necessary hand finishing. A second sheet of burlap, dragged behind the workbench, then added longitudinal texture to the concrete surface.

      The last major piece of equipment in the paving train was the dual purpose Guntert & Zimmerman TC 600 texture and curing 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 600 then made a second pass to and applied of Meadows curing compound to seal the surface.
     Concrete was produced by a dedicated Rexcon drum mix concrete plant, set up near the mid-point of the job. This is the company's biggest portable plant, with an individual batch capacity of 8 m3 and hourly production capacity of up to 300 m3. From there concrete was delivered to the paver by a fleet of up to 15 open tandem trucks. Overall, Côté reports an average system production rate of 1800 to 2200 m3/day for the project. Equally important, the system delivered pavement smoothness of 12 mm/100 m (120 mm/km) compared to a specified limit of 240 mm/km.
     Côté emphasises that close attention has been paid to joint design on this contract to deliver joint durability of up to 15 years. For transverse joints, a 3 mm relief cut is made between 8 and 12 hours after concrete placement. Fourteen days later, a larger cut is made using a ride-on saw to ensure that the tight dimension tolerances of the joint slot are met. The saw cut then receives a high volume pressure wash, followed by sandblasting to roughen the vertical sides and remove any residual dust. Preformed neoprene is then inserted into the joint after lubrication with a small quantity of adhesive. Joint integrity is maintained by using a single continuous piece of neoprene across the full pavement width to avoid any neoprene joints. Côté adds that, unlike conventional transverse joints where the poured sealer is stretched between the concrete sidewalls of the joint, the neoprene joint material remains in compression to provide long-term joint flexibility. The longitudinal relief cut is completed in a similar manner to the transverse cut and also enlarged 14 days later. In this case the cut is enlarged by a conventional walk-behind saw and hot bituminous sealer is poured into the longitudinal joints once nearby transverse joints have been completed.
     Support mobile equipment included Alva Construction's fine grading fleet of two graders, two water trucks and three compactors. Alva utilised Caterpillar 14G and 140G machines, while the compactor fleet consisted of SuperPac 840, Ingersoll-Rand Pro-Pac 100 and Caterpillar CS-563D machines. Also ahead of the paver, a bucket equipped Caterpillar IT28G was kept on standby to move dumped concrete if required. Material sources for the contract included two wayside granite quarries for all base materials, while non-reactive concrete aggregates were supplied by Gateway Materials Ltd. (two sizes of coarse aggregate) and V. J. Rice Concrete Ltd. (fine aggregate).
     Demix Construction and Dufferin Construction are business units of St. Lawrence Cement Inc. Demix Construction managed the project, while Dufferin Construction completed concrete paving.

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Expanded asphalt with HMA overlay protects road assets for Ontario city

By Andy Bateman, Engineering Editor

    Grader-laid expanded asphalt is proving to be a cost effective pavement rehabilitation method for the City of Burlington as well as an integral part of the city's asset management program.
     Dave Youkhana, Quality Control Coordinator in the Design and Construction Section of Burlington's Engineering Department, explains, "Our challenge is to maintain the city's extensive and rapidly growing road network on a limited maintenance budget. We have found that an expanded asphalt base combined with a hot mix asphalt surface overlay provides a cost effective pavement rehabilitation method.
     "At the same time, we recognise the environmental benefits of a process that reuses existing road material and thereby minimizes the use of virgin material." On a recently completed project, for instance, over 30,000 m2 of pavement was rehabilitated by this method in a mature residential suburb known as Birdland. Here, the condition of several streets had deteriorated in recent years, despite relatively low traffic volumes and a number of surface repair treatments, including straight hot mix overlay, tar and chip, patch repair and crack sealing. (See sidebar on City of Burlington Asset Management.)
     Expanded asphalt stabilization work on the Birdland contract was completed by Hard Rock Pavement Recycling Inc. of Port Colborne, Ont. Ron Carleton, Hard Rock's expanded asphalt supervisor, explains that the stabilization process was completed in two stages. During stage one, the existing pavement was pulverized, compacted and graded in preparation for expanded asphalt stabilization. In stage two, a portion of the prepared surface was then remixed with expanded asphalt cement, spread by grader and compacted to produce a stable expanded asphalt base. Specifications here called for an expanded asphalt thickness of 150 mm, with any material sized above 50 mm to be removed from the surface of the expanded asphalt mix during stage two of the operation.
     Leading off stage one were Hard Rock's two pulverizers, CMI RS-650 and RS-800 units. Each machine pulverized 50-75 mm of old asphalt together with 75-100 mm of underlying granular base material to produce a homogenous mixture. In some locations, a specified quantity of supplemental virgin aggregate was applied to the existing road in advance to ensure that the pulverized mixture met the required gradation. Behind each pulverizer, a water truck provided a light water spray to assist in compaction and minimize the pick-up of loose material. (Carleton notes that higher volumes of water are often necessary to reach the specified moisture content, in which case the pulverizer pushes a water truck). After water spraying, a heavy pneumatic roller was used to compact the pulverized mixture and provide a temporary running surface for traffic during construction. The surface was then fine graded to ensure a good match with adjacent driveways and utilities after final resurfacing. Behind the grader, rubber and dual steel drum compactors provided further compaction up to a Bulk Relative Density (BRD) of 2.15 tonnes/m3.
     For stage two, the larger of the two pulverizers, the RS-800, went into action again, this time connected to a 40 tonne capacity tanker containing Petro-Canada 58-28 PGAC asphalt cement at 190ÁC. Cold water was then injected into the hot asphalt cement in the RS-800's reaction chamber at a rate of 2 per cent of the mass of asphalt cement. The resulting asphalt cement froth was then metered into the drum of the pulverizer at a rate of 3 per cent of the mass of the reclaimed asphalt pavement (RAP) and granular mixture.
     The expanded asphalt froth and recycled material were mixed and blended in the pulverizer drum and discharged at the rear of the machine. The expanded asphalt base then received a light water spray before compaction by the dual steel drum and pneumatic machines. Stage two was wrapped up by further fine grading and compaction with the pneumatic compactor and dual steel drum roller to achieve a smooth matching surface with a specified density of 97 per cent of the BRD of the mix.
     In terms of strength, the expanded asphalt base has a Granular Base Equivalency (GBE) of between 1.6 and 1.8, compared to 1.0 for granular base and 2.0 for hot mix asphalt. Hard Rock's Brian Mountjoy adds, "The pneumatic roller is generally used prior to final compaction with the steel drum machine. We believe this sequence provides an opportunity for the rubber tires to knead the material at greater depths prior to the steel drum roller smoothing the surface and creating any "bridging" of the mixture. If the total liquid content is in the range of 8 per cent there is sufficient liquid to provide lubrication to achieve optimum compaction. The mixture does not require time to "cure", however this total liquid content of 8 per cent may create a mixture which is tender. Given 24 hours without precipitation, the mixture will stabilize sufficiently to allow for a hot mix overlay."
     Hard Rock's grading and compaction fleet, all Caterpillar units, included a 140G grader, CS-433C single drum and CB-634C dual drum steel compactors as well as a PS-300B pneumatic compactor. On this contract, Burlington-based general contractor King Paving Ltd. applied the 50 mm lift of HL3 surface asphalt.

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Roadbuilding job compares in-place asphalt recycling techniques

By Andy Bateman, Engineering Editor

  A recent roadbuilding job awarded by the Ontario Ministry of Transportation provides a rare opportunity to compare the long term performance of cold-in-place recycling with paver laid expanded asphalt.

     Valued at $4.35 million, MTO contract 2002-4040 involved grading, drainage, granular base and hot mix paving on a 15.1 km section of Highway 7 east of the Town of Perth, beginning at the municipality's eastern limit. As originally envisaged, the job included a 50 mm lift of HL1 surface asphalt laid directly on a 110 mm lift of cold-in-place recycled (CIR) material. Later, a change proposal resulted in a 5 km experimental section at the west end of the job being completed instead with 110 mm of expanded asphalt, while the eastern 8 km section was completed with CIR as originally planned.
     Each in-place recycling method has been applied to the same depth, in both travel directions and both sections received a 50 mm lift of HL1 hot mix surface asphalt. In addition, both contractors involved in the recycling work brought extensive experience to the job: Miller Paving Ltd. completed the CIR section, while Roto-Mill Services Ltd. (part owned by Aecon Construction and Materials) completed the expanded asphalt section. Aecon then completed the HL1 surfacing on both sections. Shoulders, passing lanes and intersections received more conventional treatment consisting of granular A base material followed by two lifts of medium duty binder mix, 50 mm and 40 mm, and the HL1 surface mix.
     In Miller Paving's cold-in-place recycling train, a CMI PR-1000 pavement profiler pushed an emulsion tanker while simultaneously milling 110 mm of existing asphalt. Milled material was then conveyed to the towed United Machinery mobile crushing and screening unit where all the material is reduced to minus 38 mm. From there, the sized material was transferred to a towed Midland 800 Mix-Paver where it was mixed with conventional polymer modified asphalt emulsion, pumped directly from the tanker to the paver's self-contained pugmill. The recycled mix was also laid down by the Mix-Paver, utilising its standard paving screed and electronic controls. The material was laid to a depth of 100 mm as the driving lane was slightly widened from 3.5 m to 3.75 m. Behind the paver, a Dynapac 302 single-drum vibratory compactor and a Dynapac CP 271 pneumatic roller compacted the recycled mix. The average production rate of this train was 200 to 300 tonnes/h, depending on the local profile correction.
     For the expanded asphalt section, Roto-Mill utilised its paver laid expanded asphalt recycling train. This train included the Roto-Cycler, an integrated portable unit that both processed recycled aggregate and produced expanded asphalt. (See Aggregates & Roadbuilding, September/October 2002 edition for additional information). The expanded asphalt was then laid to the required width and depth by a paver travelling directly behind the Roto-Cycler. In a change from last year, Roto-Mill teamed the Roto-Cycler with a new European-built Vùgele Super 2100 paver having, according to manufacturer's data, a laydown rate of up to 1000 tonnes/h. Roto-Mill's paver is fitted with an extending screed that incorporates a tamper and two pressure bars and has a maximum rated mat width capability of 9 m. According to Dan Hanley, Roto-Mill's Marketing & Product Development manager, the switch helped the company Roto-Mill complete the expanded asphalt portion of the job in three days. "Paving productivity has increased by up to 30 per cent in ideal conditions on this and other partial depth projects, while productivity has increased by 20 per cent on average for all depths. The paver delivers very high initial compaction immediately behind the screed, thereby eliminating the need for the fourth and the sometimes the third pass with the breakdown roller on some partial depth projects. Not only that, there is reduced secondary finishing and rubber tire roller time as well."
     Aecon Construction and Materials completed a 50 mm HL1 surface lift on both the CIR and paver laid expanded asphalt sections of the Highway 7 contract. Aecon's paving train included a Roadtec SB-2500 Shuttle Buggy, Caterpillar AP 1000B paver and Caterpillar PS 300B pneumatic compactor. Aecon superintendent Pat Goody reports that the weather played a key role when it came to final surface paving of the respective sections. On the expanded asphalt section, HL1 could be paved within 2-3 days after the expanded asphalt train has passed through. By comparison, it was sometimes a challenge to meet all job requirements on the CIR section during one wet spell. These requirements included a minimum 14-day exposed period for curing and a moisture content of 2 per cent or less, as well as completion of HL1 paving within 30 days. Fortunately, several days of continuous hot dry weather provided the necessary drying for HL1 paving to proceed.
     In general, proponents of expanded asphalt note that the finished mat of expanded asphalt requires typically only 24 hours of curing and can be paved immediately with the final surface lift of hot mix or other surface treatment applications. However, as Miller vice president Stephen Damp points out, "There are now at least two manufacturers who are producing fast curing emulsions for cold in place recycling. As a result, the traditional 7-14 day curing period is being reduced to 4-7 days, much closer to the expanded asphalt process curing."
     Either way, CIR and expanded asphalt are both well proven-pavement rehabilitation methods whose construction phase represents only a small percentage of the pavement's expected service life. As to the actual service life for each method on this particular contract, time will tell.

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November/December 2003 issue

Aggregates and Roadbuilding Magazine
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