Canada's “Rock to Road” Magazine

March/April 2004 Issue

• Mobile crusher key to efficient concrete reclaiming
• Recycling - part of doing business for roadbuilder
• Camaro Enterprises garners Ontario Paver of the Year Award
• Superpave experience provides valuable insights

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

Mobile crusher key to efficient concrete reclaiming

By Andy Bateman, Engineering Editor

For one demolition contractor, multiple stages of rebar removal and a track mounted crusher are key components of a successful concrete reclaiming process.

    One of the main challenges in reclaiming concrete from a concrete structure is the separation of the concrete from its embedded rebar. Effective separation translates into steady output from concrete crushing plants, uniform crushed product and maximum recovery of both concrete and steel. Poor separation, on the other hand, can mean awkward manual work and crushing delays while jammed rebar is removed, as well as potential damage to rubber conveyor belting and other components.
     Aggregates & Roadbuilding recently visited the set up used by Priestly Demolition Inc. on a major job at Toronto's Rexdale Mall, where the company's successful process incorporated rebar removal and sorting at virtually every stage in a multi-stage reclaiming process. Priestly's contract called for demolition of the entire concrete structure, including a two-storey parking garage under the south end of the mall. Reclaimed concrete was hauled to an on-site mobile crusher for reduction into Granular B base aggregate, while the rebar was sold for scrap.
     Working space was tight, as the mall was still partially occupied and a surface parking lot on the mall's east side was still in public use. In the interests of public safety, the entire concrete crushing process, including concrete feed stockpile, granular product stockpile and a mobile crusher were all contained in a fenced staging area at the east edge of the mall property. The resulting small processing area necessitated frequent crusher moves to process the narrow feed stockpile, while also limiting manoeuvring room for trucks delivering feed material.
     Down in the parking garage, three pieces of equipment tackled the heavily reinforced concrete structure. A Komatsu PC400LC excavator was on wrecking duty, utilising the extra reach provided by its third member JRB shear, while a Komatsu PC300LC was fitted with a grapple for cleaning and sorting material, including rebar. Behind the PC400LC, a Link-Belt Quantum 8000 excavator, fitted with a pulverizer attachment, was breaking the concrete of the collapsed slab into some 154 cm2 square pieces. Meanwhile, at the west side of the job, a Link-Belt 4300 excavator, fitted with a conventional excavator bucket, was loading two Volvo A25C articulated dump trucks hauling pieces of previously broken concrete to the staging area for crushing. On arrival there, the A25Cs reversed up the steep feed stockpile and discharged in front of another Komatsu PC400LC stationed on top of the pile. Fitted with a pulverizer attachment, this PC400L provided further sorting and rebar removal prior to crushing. Behind this machine, a Link-Belt 2800 Quantum excavator was also positioned on the feed stockpile, within reach of the mobile crusher's feed hopper. On this occasion, the 2800 was fitted with a conventional 1.1 m3 bucket, although the bucket feeding the crusher would normally be fitted with a thumb to provide yet another opportunity for rebar sorting.
     Priestly's mobile crusher was a track-mounted Extec Mega-Bite 1100x700 mobile jaw crusher. During crusher operations, two operators were stationed over the jaw feed to remove rebar by hand, while a Master Magnets Ltd. overhead magnet on the plant's discharge belt removed any residual rebar from the Granular B product stream. At a 75 mm closed side setting, the jaw set was typical for a concrete crushing application, reducing the 610 mm feed material to 100 mm minus. Foreman Brian Priestly puts average plant throughput here at 800 tonnes/d, adding that overall throughput rate varies considerably from contract to contract depending on feed size and rebar content.
     Now in its fourth year of service, this UK-built plant has crushed nearly 500 000 tonnes for Priestly. The belt under the jaw is a conventional rubber belt, and the fact that the belt has reportedly lasted some 2.5 years without being torn or slit by rebar underlines the effectiveness of Priestly's rebar removal process. In-house refinements to the mobile crushing plant include the addition of aluminum strips to the magnet's belt and the replacement of a steel plate near the magnet with a (non-magnetic) stainless steel plate. The overhead canopy, also an in-house addition, is removed for travel while the hinged back and sides of the feeder are lowered.
     Company president Ryan Priestly reports that the jaw can be running within 2 hours of arriving on site and prepared for travel in a similar time frame. Priestly adds that the crusher fits well into job scheduling, "With this unit we can start crushing quickly and crush material as it generated through the duration of the job. This flexibility is useful on demolition sites as we are often working in relatively tight locations. For instance, if we attempted to use a larger crusher, we would then have to stockpile a large volume of feed material in advance to make the crushing process efficient. As a result, we would have a peak in our crushing schedule as well as increased space requirements and increased material rehandling."
     Manufacturer data states that Mega-Bite 1100 x 700 crusher is fitted with a horizontal grizzly feeder 4 m long by 1.1 m wide having two stepped grizzly sections. The feeder's rated capacity is 120-360 tonnes/h. The jaw itself is a single toggle design with a feed opening width of 1100 mm and a gape of 700 mm (44x28 in.). The jaw has a minimum and maximum discharge setting of 70 mm and 200 mm, respectively. Jaw product discharges onto a conventional rubber belt 1 m wide and 9.9 m long, operated by a hydraulic drive.
     Other standard equipment on the Mega-Bite includes a 3 m or 9 m long fines side conveyor, a dust suppression system, fully remote control, hydraulic jacking legs, and a magnet. A 6-cylinder Deutz diesel engine powers the plant. Ready for transport, the unit weighs less than 50 tonnes, is 2.74 m wide excluding side conveyor, 4.06 m high and 13.9 m long. If required, the crusher's radio control system allows a single operator to both load and manoeuvre the crusher from the feeding excavator. Manufacturer's literature also describes a UK application where the crusher was teamed with one of the same manufacturer's Robotrac track mounted screening plants to produce an integrated mobile crushing and screening system.
     Priestly Demolition Inc. is based in Aurora, Ont. Since its founding in 1963, this family owned business now has 150 employees and an extensive equipment fleet that includes 40 excavators, 10 bulldozers and 20 skid steer loaders.

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Recycling - part of doing business for roadbuilder

By Andy Bateman, Engineering Editor

The recycling of both reclaimed asphalt pavement (RAP) and concrete has been an integral part of one Toronto roadbuilder's business for many years. The latest process refinement, a RAP fractionating plant, has delivered further improvements and optimized the use of RAP in recycle asphalt mixes.

    Gazzola Paving Ltd. has been recycling materials since 1985, taking advantage of the company's large Etobicoke yard to stockpile and process reclaimed asphalt as well as concrete. Considerable quantities of recycled asphalt and concrete material are processed annually. RAP is received either as surface millings from resurfacing projects or in large broken pieces from full depth road reconstruction projects. The larger material is crushed and screened into graded material by area crushing contractors for subsequent use as a raw material in recycle asphalt mixes or as granular base aggregate. Of last year's RAP total, some 50 000 tonnes was incorporated into recycle mixes by Gazzola's hot mix plant, 30 000 tonnes utilised as granular base aggregate and about 20 000 tonnes kept in inventory. In parallel with the RAP operation, all reclaimed concrete brought in from highway, sidewalk and demolition projects is crushed and screened into granular base aggregate for use in commercial applications.

RAP recycling
    Speakers at the recent Ontario Hot Mix Producer's Association (OHMPA) asphalt seminar noted that fractionating RAP into various sizes delivers a number of benefits. These include improved control over both the asphalt cement content and RAP aggregate gradation in recycle mixes, as well as the ability to select the RAP fraction for the most economical mix. As one speaker said, "Hot mix producers wouldn't think of combining all virgin aggregates sizes into a single feed bin to feed a hot mix plant, but many use a single bin for RAP". Gazzola is already there, having commissioned a RAP fractionising plant and separate RAP feed bins at its hot mix asphalt plant last year in time for the 2003 construction season. The fractionating plant's job is to separate recycled asphalt feed material, either surface millings or 19mm minus granular RAP, into three fractions; 19 x 9.5 mm, 9.5 x 4.75 mm and 4.75 mm minus. Any combination of these fractions can then be fed to the 400 tonnes-h capacity Astec/Barber Greene DM 71 combination drum/batch/coater plant via three RAP feed bins.
     Laboratory supervisor Solomon Andualem explains that the fine RAP fraction contains the highest percentage of asphalt cement, as the particles in this fraction have the highest surface area originally coated with asphalt cement. After laboratory analysis to confirm the asphalt content and gradation of each fraction, the RAP is incorporated into a recycle mix design. For instance, a mix design may originally specify a 5 per cent virgin asphalt cement content (50 kg/tonne) and 40 per cent virgin sand. The available RAP contains 5 per cent asphalt cement in its 4.75 mm minus fraction. If this RAP fraction is utilised to replace half of the required sand, the fine aggregate content of the resulting RAP mix will consist of 20 per cent RAP and 20 per cent virgin material. As a result, the RAP provides a 1 per cent reduction in the amount of virgin asphalt cement required (20 per cent of 5 per cent), as well as a 20 per cent reduction in the virgin sand required.
     With typical virgin asphalt cement costs of about $300/tonne, the RAP use translates into asphalt cement savings of about $3.00 per tonne of new hot mix asphalt, and up to $2.00 in virgin sand savings. These savings in virgin material costs are offset by the costs associated with hauling and processing RAP, but the overall result is still a significant saving in hot mix raw material costs.
     To further improve the efficiency of their RAP operations, some users are storing RAP in open sheds, thereby keeping its moisture content as low as possible. RAP's moisture absorption is high compared to virgin aggregates as it consists of various particle sizes cemented together by the original asphalt cement. According to one OHMPA speaker, a 1 per cent increase in RAP moisture content increases material drying costs by up to 13 per cent. Where stockpiles are exposed, a large conical pile provides more effective drainage than long straight or flattened piles. To some extent, exposed RAP piles are self-covering as a surface crust forms over time. This crust can easily be broken through with a loader or backhoe bucket to expose loose material when required.

Concrete recycling
     Granular base aggregates produced from crushed reclaimed concrete are popular with site crews as the fine cement fractions already present in the concrete facilitate compaction into a dense base with a smooth surface. At Gazzola's yard, crushing contractor Robert Young Construction Ltd. was recently producing Granular A base from a stockpile of reclaimed concrete containing slabby pieces up to 1.2 m wide and 450 mm thick. On top of the stockpile, a Daewoo 280LC-III excavator sorted and loosened material, while a Caterpillar 950G wheel loader baled the loosened material over the edge of the stockpile. From there, it was fed to a Cedarapids crushing spread at a reported average rate of 250 tonnes/h by a Caterpillar 980G.
     Like all of Young's primary units, the Cedarapids 30x42 primary jaw was fitted with a custom designed telescopic tower carrying a Breaker Technology Inc. boom and breaker system to deal with jammed or bridged material. The jaw itself was run at a tight setting, reducing material to 102 mm minus. From there, crusher run was transferred onto the secondary plant feed conveyor, where any plastic, wood or other waste material was removed manually and an Eriez magnet removed any remaining rebar. Material arriving at the Cedarapids 855 secondary plant discharged onto a small pre-screen where product already smaller than 25.4 mm was directed through side chutes to the spread's product conveyor. Meanwhile, any larger material fell onto a grizzly that distributed material between the upper and lower screen cloths on the secondary's main 1.22 m x 4.27 m screen. Material larger than 64 mm retained on the upper screen passed through a 12x42 jaw crusher, while material larger than 25 mm (retained on the lower screen) was directed to a 3030 roll crusher. Material from both crushers was returned to the secondary feed conveyor on a common return belt and elevating wheel for further processing into finished product.

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Camaro Enterprises garners Ontario Paver of the Year Award

By Andy Bateman, Engineering Editor

Excellent roadbuilding was again recognised at the Annual Ontario Roadbuilders' Association (ORBA) convention, held this year at the Fairmont Royal York Hotel in Toronto on February 2-4, 2004. Award winners, including the provincial Paver of the Year, received awards for their performance on contracts in each of the Ontario Ministry of Transportation's five regions.

      Camaro Enterprises Ltd. has won the prestigious Ontario Paver of the Year Award and Northwestern regional award for an outstanding performance on its first Superpave job, MTO contract 2002-6012. Most of this $10.2 million contract was located on a 24.5 km stretch of Highway 17 east of Dryden beginning on December 14, 2002 and completed by September 19, 2003. By all accounts the award was well earned, with a quality job completed despite difficulties posed by severe winter weather, existing pavement conditions and even utility pole locations. The extensive scope on this job included two curve revisions, 137 607 m3 of earth excavation and 46 243 m3 of rock excavation, while hot mix asphalt quantities included 41 872 tonnes of Superpave 12.5 mm mix and 36 024 tonnes of Superpave 19 mm mix. Additional quantities included 170 180 kg of granular sealing, 225 584 m2 of in-place full depth reclamation, 22 286 tonnes of partial depth reclaim asphalt.
     Vice president of operations Derek Walker explains that the contract closed on September 18, 2002 with a September 19, 2003 (one year) completion date. Camaro had the necessary documents in place and signed to begin work on October 30, 2002 but did not mobilize as the frost was already setting in and daylight hours were limited. As a result, the company had to complete aggregate crushing and begin earth and rock excavation in very unfavourable conditions in order to meet the completion deadline. Extremely cold winter weather made any outside work very difficult. "Crushing of the bituminous materials and granular occurred when temperatures dropped to a frigid Æ50ÁC. Several crushing shifts were suspended due to crusher inoperability in the freezing temperatures and equipment maintenance was especially difficult. Traffic control was also a challenge, with personnel requiring breaks as frequently as every 20 minutes due to wind chill. Finding personnel willing to work in such conditions was difficult."
     The cold winter turned to a cold spring, with the result that Camaro was ditching in sub-zero temperatures throughout March and April. This necessitated the use of heavy hydraulic excavators such as John Deere 450 and Caterpillar 345 and 330 machines to complete scratch ditching in the frost hardened ground. Most of the rock work was also completed between February and April.
     The cold weather also impacted on hot mix asphalt production, as aggregates stockpiles at the asphalt plant were found to contain layers of snow and frost. In response, it was decided to excavate and re-stockpile the aggregates to ensure uniform feed for the Superpave mixes, a process that also entailed the testing of stockpile working faces several times a day. Fortunately, the summer was unusually dry and no days were lost to rain between May and September, although the resulting heavy summer tourist traffic did require careful handling. A typical day saw six separate operations working on the 24-km section of highway, necessitating precise co-ordination of traffic crews to both minimize traffic delays and maintain productive truck cycle times. Further difficulties were posed by hydro pole relocations. Walker explains, "The utility relocates required for the contract were completed in the 2002 construction season. However, as blasting operations progressed it was noted that several stretches of utility poles in the work area were close to the planned rock faces in the blast areas. In some cases, poles were within 2 m of the blasts, while others were actually inside planned blast area. Poles were relocated where possible, with one rock cut bypassed until July while waiting for pole relocation. In other areas, where relocation was impossible, the blasts were kept small and well controlled. However, the overall impact was reduced production by the rock excavation crew and further scheduling conflicts in an already tight schedule."
     When in-place pulverizing began, Camaro and subcontractor Hard Rock Pavement Recycling Inc. discovered that the existing asphalt depths were as much as 300 mm thicker than stated in the plans. Rather than the anticipated 100 mm of Granular A base underneath the existing asphalt surface, Hard Rock encountered 200 mm minus cobble material as well as granular material in the existing roadbed. Not surprisingly, this oversize material and thick asphalt reduced the production rate of Hard Rock's CMI RS-800 cold planer by 30- 50 per cent, an unanticipated slow that meant rescheduling of the Granular A placement and asphalt crews. To assist Hard Rock, Camaro cored ahead of the cold planer and attempted to partially reclaim areas where excessive asphalt depths were encountered, although there were still variations in asphalt depths of 50Æ300 mm from centreline to shoulder. As a result, Camaro received permission to apply a minimum of 100 mm of Granular A on top of the reclaimed surface to provide an adequate base for the subsequent asphalt lifts.
     Walker attributes the overall success of the project to excellent communication and teamwork between project superintendent Jeff Tait, Thunder Bay Testing and Engineering (the consulting engineers) and the contract's various supervisors and sub-contractors. "The numerous challenges faced could have stopped work, had Camaro and its subcontractors been unable to respond as quickly and efficiently as they did. All of the operators and drivers on the project did an excellent job, especially in the cold winter and spring months. A special mention goes to the survey crews who were able to stay ahead of the operations, as well as traffic control crews who kept traffic moving through the busy 24-km section. The successful asphalt placement operation was due to excellent communication and teamwork displayed by asphalt supervisor Darryl Boulanger, laboratory supervisor Simone Haquoil, plant operator Greg Bucas and screed operator Russ Carlson."
     Turning to equipment, hot mix asphalt was produced by Camaro's portable CMI UVM 1700 plant with a capacity of 320 tonnes/h. Micro Motion controls added to the asphalt pump and belt on this hot mix plant are said to provide AC delivery accuracy within 0.01 per cent.
     On site, a Cedarapids CR551 RX Remix paver achieved peak and average production rate of 380 tonnes/h and 270 tonnes/h, respectively. Behind the paver, Camaro's compaction train included a Caterpillar CB-634 dual steel drum breakdown roller making two passes. A Dynapac CP-21 pneumatic roller in the secondary position made three passes, while a Bomag BW164 AC-2 combination finishing roller was used as required.     Asphalt cement was supplied by McAsphalt Industries Ltd.'s Thunder Bay terminal, while both fine and coarse asphalt aggregates were sourced from the MTO pit, Dyment 48. The same pit supplied over 200 000 tonnes of Granular A base material, in addition to over 200 000 tonnes of Granular B base.
     Project superintendent Jeff Tait concludes with a few salient comments on the company's first experience with Superpave. "The coarse texture of Superpave asphalt is conducive to heat retention. This combination of heat and strength made paver stops and starts very manageable as the screed did not sink and rise as noticeably as with conventional mixes. On the down side, the coarse nature of Superpave created excessive wear on the asphalt plant and paver. It was also found that the Superpave mix responded best to compaction equipment at a road temperature of 130ÁC, so we ran the roller train closer to the paver than on conventional mixes." To that Walker adds, "The stringent criteria in place for Superpave asphalt mean that consistent material production is critical. Ideally, Superpave contracts would be tendered in a manner that would allow paving to be completed during good spring and summer weather and so avoid late fall paving."

Northeastern Region
     Miller Paving Northern won the MTO's Northeastern regional award for quality roadbuilding on MTO Contract 2002-5115, a Superpave contract that has the added distinction of incorporating the MTO's cold temperature test site. The purpose of the test site is to assess the cold weather performance of a number of different asphalts and provide data for improved low temperature asphalt cement classification.
     The overall contract was located on a stretch of Highway 655 between Timmins and Cochrane, beginning 27.4 km south of Highway 655's junction with Highway 11 and extended northerly for 13.4 km. Prime contractor M.J. LaBelle Company Ltd. was responsible for construction, while Miller Paving was responsible for all of the paving, acquisition of the modified asphalt cements, asphalt cement transport, storage, hot mix production and the staging of the paving work for the test sections. Asphalt quantities included over 15 000 tonnes of Superpave 19 mm binder course mix and over 12 500 tonnes of Superpave 12.5 mm surface mix.
     The test site itself included seven test sections, each 500 m long and two lanes wide, with paved shoulders and curve widening in some cases. A different manufacturer supplied the Performance Grade Asphalt Cement (PGAC) for each section. A control section utilised unmodified 52-34 PGAC, while the other six utilised different modified asphalt cements graded at 64-34, except one where a 58-34 PGAC was used. All seven sections used the same job mix formula (for each lift) as the rest of the contract.
     Andy Desmarais, Miller's asphalt superintendent, explains that one of the biggest challenges faced in the construction of the test sections was learning how to handle the asphalt cement products supplied by different manufacturers. "Each mix had its own characteristics and mixing temperatures and reacted differently to production, placement, and compaction procedures." In addition, Miller's quality control staff faced the additional challenge of obtaining and testing an unusually large number of samples for acceptance testing and research purposes. Each test section was considered to be a lot with three sublots, with a sample required from each sub-lot and from both binder and surface courses. Under normal paving conditions, only one sample from each lift would have been required for the equivalent area of each of test section. The MTO also required no less than twenty samples from each test section for research purposes, with ten samples taken from each course. To tackle this massive sampling job, Miller constructed a trailer mounted sampling bin that worked well and allowed all the samples to be taken without any interruption to paving operations. Use of the sampling bin also meant that samples could be collected without disturbing the freshly placed mat, thereby eliminating the need for any handwork in the sampling areas. Due to the complexity of scheduling and coordinating the delivery of the different PGAC's to the hot mix plant, just two test sections a day of one lift each could be paved. After each test section, any binder remaining in the plant's AC storage tank had to be purged in readiness for the next AC, some of which had arrived very cool after a long haul in a small tanker. As a result, Miller had to heat jacket all of the plumbing from the storage tank right to the tanker's off loading hose, using the shortest hose possible. The weather did nothing to make the AC delivery and construction scheduling task any easier, with company records showing rain for at least 40 per cent of the contract duration.
     Equipment used on this project included the company's Cedarapids 360 tonne/h capacity 8828 portable drum mix plant, set up 3 km south of the contract. On site, a Roadtec SB 2500 Shuttle Buggy fed material to a Cedarapids CR-451 paver and the sampling bin as required. The CR-451 was fitted with Topcon System 4 automatic grade and slope controls to facilitate placement to the required elevation and cross fall. Miller's compaction fleet included a Bomag BW211D dual steel drum vibratory compactor and two Caterpillar PS300B pneumatic units. Asphalt superintendent Desmarais credits the uniform finished pavement to the combination of a dedicated paving crew and the SB 2500. Miller achieved full bonus for smoothness under the MTO's End Result Specification (ERS) system, as well as bonuses for mix properties and compaction.
     Miller personnel also involved in this successful contract included Eric Desbiens, general manager, Herb Villneff, senior quality control manager, Shayne Toye, asphalt foreman, Al Pascoe, plant foreman, Steve Lescom, portable plants manager and Britt Herd, chief estimator. Credits also go to subcontractor M.J. Labelle for a key role that included all earth excavation, granular grade raises and road widening as well as aggregate crushing and supply. Miller Paving Northern is a division of the Miller Group.

Southern Region
    Huron Construction Co. Ltd. won the Southwestern Regional Award for its work on MTO contract 2003-3021 on Highway 401. This $2.2 million resurfacing job on Highway 401's eastbound and westbound lanes called for a Recycle Premium Dense Friction Course (DFC) mix to be laid on a 13 km stretch, beginning 0.6 km west of Belle River Road and extending east to 1.2 km west of Highway 77. Additional work included rumble strips and granular sealing. The contract lasted just 35 working days from July 21 to September 25 last year, including 4 days lost to rain.
     Contract manager/plan administrator Joe Doyle reports that designing a Recycled Premium DFC Mix from the existing Reclaimed Asphalt Pavement (RAP) proved to be a challenge. "We found it difficult to obtain the necessary mix voids content utilising the DFC RAP from this contract in the required 30 per cent recycle/70 per cent virgin aggregates ratio. However, we were successful in designing a mix with the somewhat lower recycle ratio of 20 per cent RAP. Once on site, all the construction processes including milling the RAP, producing the recycle mix, paving, painting and reopening to traffic were subject to tight time constraints. Due to traffic volumes, we had to be off the road by noon of Fridays so in practice we found it most effective to work four long days." Doyle adds that contract specifications also included a smoothness specification for the finished surface, although the job consisted solely of the single 40 mm resurfacing lift.
     The successful completion of this job is credited to the hard work of everyone involved including administration staff, shop mechanics, crushing crews, paving crews, lab crews, with special mentions to assistant plan administrator William Snowdowne, contract superintendent Andrew Lawrence and paving foreman Joe VanVaerenbergh. Doyle highlights the role played by the traffic control crew, whose constant adjustments to traffic control devices kept traffic moving while maintaining safe construction zones. Additional credits go to excellent communication, job planning and teamwork between subcontractors, Delcan Consulting and Ministry staff.
     On site, subcontractor Miller Paving Ltd. utilised Wirtgen 2200, 2100 and 1000 milling machines to first remove the top 35 mm from the existing surface. The 29 106 tonnes of 20/80 DFC Premium Mix required for the job was produced by Huron's 250 tonnes/h capacity Boeing 200 drum mix plant utilising McAsphalt Industries Ltd.'s 64-28 PGAC combined with fine and coarse aggregates from Ontario Trap Rock (R.W. Tomlinson Ltd.). Hot mix arriving on site was fed into a rental Roadtec SB-2500B Shuttle Buggy that in turn discharged into a Cedarapids CR451 Remix paver fitted with Topcon automatic screed control and a non contact ski. Compaction equipment included a Caterpillar CB543C breakdown roller, Caterpillar PS-360B pneumatic roller and Bomag BW161AD finishing roller.
     Huron Construction is part of the Miller Group.

Central Region
     The MTO's Central Region award went to K. J. Beamish Construction Co. Ltd. for quality workmanship on MTO contract 2002-3020. This contract, valued at $4,026,660, was located east of Orillia on Highway 12 and County Rd. 44, extending from 0.5 km west of Creighton St. easterly to 0.2 km east of Balsam Rd. and lasting from April 22, 2003 to October 27, 2003. Beamish's Paul Hayward reports that the contractor had to deal with high traffic volumes, as County Rd. 44 leads to the popular Casino Rama gambling complex. Contract conditions stipulated that two lanes had to be maintained for through traffic at all times, with all work done during daytime hours only. As a result, it was decided to complete the job in stages, seven in all, necessitating careful planning and cooperation by all involved. Hayward notes, "This was a well run project that reflected a very good working relationship between the contractor and the project administrator. A team approach was the key to good co-operation between construction and quality control personnel in keeping the project on schedule while maintaining good quality standards at all times." The Beamish team included construction manager Rick Geary, site superintendent Darryl McDonald, paving supervisor Dave Fralick and QC plan administrator John Miller.
     Hot mix asphalt for the job was supplied by Beamish's Orillia plant, a Hetherington-Berner Model 50 batch plant with a rated capacity of about 200 tonnes/h. Site paving equipment included a Caterpillar AP- 1055B rubber-track paver fitted with an Extend-A-Mat 10-20B screed. The compaction train comprised a Caterpillar CB-534C breakdown compactor, a Caterpillar PS-360 pneumatic unit and a Ferguson steel drum finishing roller. Hayward adds that compaction was monitored daily by the company's QC technician to maintain optimum rolling patterns, with these efforts rewarded by nearly full End Result Specification (ERS) bonus achieved for all mix lots.
     The total hot mix asphalt tonnage on the contract was 19 798 tonnes and included Medium Duty Binder Course (MDBC), HL4, HL1, and temporary hot mix. PGAC 58-28 and PGAC 64-28 was supplied by Canadian Asphalt Industries Inc., while fine aggregates were sourced from Beamish's Midland Pit (sand and screenings) as well as manufactured sand from the Carden Quarry of Markham Sand & Gravel, a division of Miller Paving Ltd. Coarse aggregates for the MDBC and HL4 mixes were supplied from Nelson Aggregates' Uhthoff Quarry while HL1 aggregates were hauled over 150 km from Beamish's own approved source, Bark Lake Quarry near Irondale. Beamish's Orillia Pit supplied all granular base materials, totalling nearly 120 000 tonnes.

Eastern Region
     R.W Tomlinson Ltd. won the MTO's Eastern Region award for a successful job on MTO 2002-4003, Hwy #41, Bancroft District. The job extended from Griffith northerly for 22.5 km to 0.6 km north of the intersection of Hwy #132 at Dacre, beginning on August 1, 2002 and completed on Sept 26, 2003. In addition to grading, drainage, granular base and hot mix paving, the scope of work also included structure rehabilitation and an unusually large quantity of guide rail installation.
     Weather conditions were challenging in fall 2002, with very wet and rainy conditions, coupled with early cold weather. Fortunately conditions improved in 2003 with sunny and warm summer weather that generated significant volumes of weekend cottage traffic on this two lane highway. General manager Bert Hendriks points to good work done by highway division manager Tom Smith, paving foreman Jodie Giesler and plant foreman Mike Dunphy.
     Hendricks also praises quality work by the operating crews at both the hot mix plant and on site. "The asphalt plant and crew produced quality bonus mix consistently while on site the paving crew produced a quality mat." Hendriks adds that one of the most difficult aspects of this contract was finding asphalt and base aggregates of sufficient quantity and quality to complete the project. In the event, these came from a number of sources. Coarse aggregates for the 41 150 tonnes of HL4 hot mix asphalt were supplied by the MTO pit at Dacre, Crozier's pit at Renfrew and Tom Smith's pit Foymount pit. Asphalt sand came from the Ralph Selle pit at Douglas.
     Granular A base materials, totalling nearly 110 000 tonnes, were supplied by Thomas Cavanagh Construction Ltd. (Granular A) and the MTO pit at Dacre (Granular A and Granular B). Hot mix asphalt was produced by the company's portable 360 tonnes/h Gencor Ultraplant, while on site a Roadtec SB2500 Shuttle Buggy fed hot mix to a Caterpillar AP-1000 rubber-tired paver fitted with Topcon grade controls at an average rate of 225 tonnes/h. The Caterpillar compaction fleet included CB-634, PS-300 and CB-534 units with each machine making three passes. Advance surface preparation work at intersections was completed utilising a Roadtec RX-60C cold planer.

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Superpave experience provides valuable insights

By Andy Bateman, Engineering Editor

     The recent Ontario Hot Mix Producer's Association (OHMPA) annual asphalt seminar featured three interrelated presentations on new developments concerning Superpave implementation.
      Paul Lum, director of new product commercialisation and quality assurance at Lafarge Canada Inc., explained in his paper "What mix designers have learned" that recent work included an evaluation of current asphalt aggregates to assess their fit with Superpave requirements. It was found, among other things, that the percentage of crushed faces required was dependent on mix design based on the number of gyrations and location of a mix in the pavement elevation. On the issue of using local aggregate deposits for Superpave mixes, Lum explained that local sources have been successfully used in the 50 and 75 (N design) gyration Superpave mixes that are generally required for lower traffic volumes. In locations subject to heavier loading however, 100 and 125 gyration Superpave mixes typically require washed screenings or manufactured (crushed) sand to retain the necessary air voids in the mixture. Lum added that this requirement does not represent a major change, as these high gyration Superpave mixes are used in applications similar to the MTO's existing Heavy Duty Binder Course (HDBC) and Dense Friction Course (DFC) mixes which require 100 per cent manufactured fine aggregates.
     According to Lum, there has been no difficulty in introducing RAP into Superpave mixes.
     Superpave mixes have been classified according to the nominal maximum size (NMS) of the aggregate, where NMS is one size larger than the first sieve to retain more than 10 per cent of the sample. The asphalt cement (AC) content of Superpave mixes may be determined from the Asphalt Institute manual SP2 which sets out AC content for a particular mix classification.
     Turning to equipment and testing, Lum stressed the importance of gyratory compactor maintenance and calibration, noting that sampling and sample handling, equipment calibration, equipment maintenance, internal angle and mould wear can all cause variability in test results between different gyratory compactors. A Dynamic Angle Validator (DAV) can be utilised to calibrate the internal angle of gyratory compactors and proper angle calibration will minimise variances in test results caused by differences in internal mould angles between different compactors. See sidebar, "The gyratory compactor angle issue".
     Lum concluded by describing a situation in which all calibrations and procedures, including internal angle, had been confirmed for a gyratory compactor, but where a study still obtained 1.5 per cent higher air voids. Careful measurement revealed that the internal diameter of a compactor mould had increased due to wear, with the resultant increase in mould volume largely accounting for the variance in test results.
     Kai Tam, manager of the Bituminous Section of the Ontario Ministry of Transportation (MTO) and Gary Moore, manager of the design section at the City of Hamilton, described their respective Superpave experiences on the theme "What Owners have learned".
     Tam's "MTO 2003 Update on Superpave" summarised early findings and challenges of Superpave implementation and provided an overview of a related cold temperature trial. In 2002, the MTO awarded 11 contracts with a combined total of 625 000 tonnes of Superpave mixes, of which 106 000 tonnes was placed. These numbers increased in 2003, with 16 contracts awarded (plus 1 negotiated) with 860 000 tonnes of Superpave mixes, with 1 million tonnes placed during the year. Overall, 28 contracts with 1.5 million tonnes of Superpave mixes have been awarded, of which 14 contracts have been completed with others at various stages. All the province's major contractors now have experience of dealing with Superpave mixes. Looking forward, Superpave mixes will comprise 50 per cent of the total hot mix asphalt tonnage in 2004 MTO contracts, while 2005 is targeted for full Superpave implementation.
     Tam also described the MTO's Superpave certification and training initiatives, its experience with two successful Superpave projects, and a correlation program to compare test results between laboratories. Participation in the correlation program is mandatory for MTO contracts with about 30 labs participating. So far, the deviation between test results has been much less than reported by some U. S. agencies, possibly due to the use of newer gyratory compactors and less diversity in compactor manufacturers. Ongoing challenges with respect to Superpave mix testing include the frequency of referee testing (still at a similar level to Marshall mixes) and mix checks that often show different results for voids, VMA, and stripping. Tam reports that the Best Practices Document (jointly produced by industry and the MTO), is a refinement of AASHTO protocols and should help address these issues. The now familiar issue of gyratory compactor internal angle is still a challenge, and can vary due to several factors. In response, the MTO has purchased a device to measure the internal angle of gyration and measurements are just getting underway. Additional work over winter 2003 /2004 has included the analysis of 2003 construction data for compaction and smoothness. Remaining issues and concerns include the realignment of existing HL 4 mixes with Superpave 19.0 and 12.5 mm mixes, the absence of minimum asphalt cement or stone contents for Superpave mixes, the absence of a performance test and the relevance of non-End Result Specification (ERS) Superpave attributes. In summary, the province's transition from Marshall to Superpave has been successful, facilitated by partnering through the Ontario Superpave Implementation Committee (OSIC), already advanced aggregate and mix requirements as well as established testing and design capabilities. For some mix designs, Superpave has brought about the use of better mixes through the use of higher quality aggregates to meet the requirements.
     The MTO's cold temperature trial section was completed in 2003 on a section of Highway 655 near Timmins. (For further information see article in this issue on the Ontario Paver of the Year Awards - Northeastern Region.) The trial utilised six types of binder and should provide data for the development of an improved binder grading method. Overall, the MTO is positive about Superpave implementation and will continue with its implementation as planned. Superpave specifications will continue to evolve, recognising the need for a performance test and improved binder specifications based on the cold temperature study.
     Moore's presentation described pavement management for the City of Hamilton, which consists of 6 municipalities and 15 ward boundaries having a combined total of 6065 lane km. In terms of road condition, most of the city's roads have a satisfactory rating. To maintain the overall condition index (OCI) at its current level of just under 70 would require $50 -$60 million annually, while the OCI would decline steadily over the next ten years at an annual $30 million allocation. Hamilton's experience with Superpave mixes indicates that these mixes deliver added pavement life, increased service levels and reduced maintenance costs.
     Herb Villneff Sr., manager of quality control for Miller Paving North Bay rounded out the Superpave presentation with "What contractors have learned". With respect to aggregates, Villneff noted that more attention will have to be paid to aggregate sources, as some local aggregates may not meet the requirements needed for Superpave mixes. For instance, some of the new tests that must be done on aggregates for Superpave mixes, such as Fine Aggregate Angularity and the Sand Equivalent test may prohibit the use of some of the local aggregates.
     With respect to mix designs, Villneff noted that because aggregates for Superpave mixes must meet Densification and Volumetric specifications, it can take longer to obtain an acceptable mix design. Contractors must now anticipate longer turnaround times for mix designs and try and plan their operations accordingly, which in some instances is very difficult to do given "open grade" and or pulverizing restrictions. These restrictions can become extremely costly to contractors if it becomes difficult to get an acceptable Superpave mix design.
     In terms of the production of Superpave mixes, Villneff noted that no modifications are required to asphalt plants to produce Superpave mixes and Villneff is not aware of anyone having problem in producing Superpave mixes.
     When it comes to site operations, Villneff is also not aware of any problems with the placement of Superpave mixes and, in fact, some paving crews prefer them; "These mixes stay where you put them" In other words, Superpave mixes are not tender mixes. That said, other paving crews have complained that it is difficult to make an acceptable transverse joint with Superpave mixes. On compaction, the final step in the paving process, Villneff notes that in most cases the compaction of Superpave mixes has not been an issue, as long as proper attention is given to Superpave's somewhat thicker lifts. In those areas where compaction has been a problem, it has usually been due to improper rolling procedures and/or improper roller operation, coarse mixes or late fall paving.
     Contractor's costs for quality control have increased, due to the cost of new laboratory equipment such as the gyratory compactor, additional training costs for laboratory and technician certification, waiting times for large gyratory compactor samples to cool, as well as the higher shipping costs incurred in sending large test samples to QA laboratories. Alternative methods of sampling have had to be developed, due to the larger sample sizes required for the testing of Superpave mixes, Two of these methods are the sampling bin, used only if an MTV is part of the paving train and auger sampling. Most contractors have had very little difficulty in meeting the MTO's ERS requirements with Superpave mixes and in practice some very good bonuses were achieved. However, a large percentage of the same contractors who had received bonuses under the MTO's ERS system for their Superpave mixes have also been penalized significantly for non-ERS attributes such as Nini, VMA and VFA. According to Villneff, there is a great deal of inconsistency and confusion in the way Non-ERS attributes are administered between the province's MTO Regions and even contract to contract. Villneff noted that most, if not all, of the Municipalities that have used Superpave mixes on their roadways are satisfied with the product they have received.
     All that said, Villneff concluded that Superpave mixes are the future of the hot mix industry, and as all parties concerned gain knowledge and experience, these mixes can only improve.

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March/April 2004 issue

Aggregates and Roadbuilding Magazine
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