Canada’s “Rock to Road” Magazine

July/August 2004 Issue

• Dredge operation meets tight concrete aggregate specifications
• Canada's Top 20 Quarries
• Capital Paving tackles demanding job
• Unique challenges for Winnipeg Main Street
• Poised for growth
• Customized package warrants drill performance for St Marys Cement
  

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

Dredge operations
meets concrete aggregate specifications

By Andy Bateman, Engineering Editor

A Winnipeg-based aggregate producer meets tight concrete aggregate specifications by frequent product sampling, the blending of several feed materials and refined gradation controls.

    Inland Aggregate’s CN pit is located about 14km northeast of downtown Winnipeg and one of several in the Birds Hill area. Grant Jones, Inland’s manager of Manitoba Aggregate Operations, reports that the CN pit and Pine Ridge, Inland’s other Birds Hill operation, generate about 1 million tonnes of combined sales annually. Within this total, sales of concrete aggregates from the CN pit are driven by demand from a number of ready mix concrete producers as well as Inland’s concrete pipe plant.
     Jones explains that area specifications for concrete aggregates have been tightening up in recent years, with Inland introducing a number of measures at the CN pit to meet increased customer expectations for product volume and consistency. These measures include frequent product gradation sampling, the blending of three raw materials to optimize production output and a production process that allows on the fly gradation adjustments in response to sample test results.
     Maintaining consistent product at this operation is no easy task, given a variable deposit that includes boulders up to 450 mm in diameter as well as lenses of clay. Between these size extremes the deposit is, like others in the area, variable with an overall coarse content of just 15 to 25 per cent. This variation in grading reflects the deposit’s glacial origins as an esker, where long sinuous ridges of sediment were deposited by streams running under or within a melting glacier. Jones reports that no less than 1,200 sieve analyses are now completed annually on the 20 mm x 5 mm coarse concrete aggregate, while other screened stone and sand products are tested somewhat less frequently.
     Once Inland’s QC technician has determined the current production grading, the plant operator is advised and any necessary adjustments made to keep the product within specification. Depending on the change required, adjustments can be made to the blend ratio of feed materials, the product fractions reporting to the finished product stockpiles or both. In tandem with all this sampling, Inland has improved product uniformity by limiting allowable variations in grading. When conducting a sieve analysis on the coarse concrete aggregate, for instance, particular attention is paid to the 10 mm sieve. The allowed gradation envelope for this sieve is between 30-40 per cent passing, compared to the significantly broader envelope of 25-60 per cent passing allowed by CSA specifications.
     The pit is worked wet, with the bulk of the raw feed consisting of dredged material from the pit’s main underwater extraction area. Ahead of the crushing and screening process, the dredged material is supplemented by pre-screened stone from Inland's nearby Pine Hill operation, in addition to the fine wind blown sand from the upper layers of the CN pit. The addition of the pre-screened stone increases coarse aggregate output, while the fine sand balances the relatively coarse gradation of the dredged sand.

Dredge operation
     The extraction process at the CN pit utilises an unusual German-built Federhaff-Mohr MKB 200 twin clamshell bucket floating dredge that was manufactured in 1968. This massive unit is 42 m long, 15 m wide and 29 m high with a displacement of 710 tonnes. It is equipped with a gantry and two travelling trolleys, with each trolley carrying a 5.9 m3 capacity clamshell bucket 15 m above the deck. The dredge is held in position by means of winches on each of the four corners, with cables connected to shore dead men (concrete blocks). In operation, it moves progressively towards the slumping active face, with each bucket alternately raising material from the current working depth of 24 m. Excavated material is dumped into two hoppers fitted with hydraulic grizzlies. The current grizzly bar spacing is set at 250 mm to control the maximum raw feed size going forward for processing, with the grizzlies raised periodically to discharge oversize back into the water. All the remaining feed is dewatered by twin dewatering screws and then transported to shore on the 1.1 m wide belts of a five section pin-jointed floating conveyor system. Once ashore, the feed material completes its 1.6 km journey to the processing area on a series of field conveyors.
     Adding further details to the dredging process, Jones explains that dredging capacity is a function of operating depth, with the MKB 200 operating close to its 800 tonnes/h rated capacity for 24 m deep extraction. This tonnage includes dredged sand that was formerly screened and returned to the water but now retained for processing. As an environmental protection measure, the dredge is powered by mains electricity to avoid any risk of fuel spills from diesel driven generator sets or components.

Aggregate processing
     Dredged material arriving at the processing area is first stockpiled on a primary surge pile. From there, it is recovered by a Caterpillar 980G wheel loader and dumped into the main plant feed hopper. The same loader also charges the hopper with pre-screened stone in the required ratio from a separate stockpile. Fine sand, the third raw material, is added just downstream of the main hopper and also by way of a loader fed hopper. The blended feed material is then conveyed to a Cedarapids 25x40 jaw crusher for reduction to 105 mm minus. Primary crusher run is then separated by a Simplicity inclined 8x20 triple-deck primary rinsing screen into oversize, coarse and fine product sizes. Oversize is directed to a Nordberg 1560 Omnicone crusher and returned to the screen. Meanwhile, 20 mm x 5mm coarse material from the screen passes through two 1117 mm x 10.7 m long Eagle Iron Works (EIW) log washers to dislodge any residual clay material before being screened on the plant's Simplicity 6x20 secondary screen. Gates on this screen's discharge chutes enable minor adjustments to be made to the coarse product gradation, with excess fractions diverted to separate stockpiles of clear sized product. Finished product off the screen is carried on a series of field conveyors to a Thor programmable stacker. Designed to minimise segregation, this stacker has a rated capacity of 455 tonnes/h and extends to 42.7 m.
     At the same time, concrete sand is produced from sand slurry (5 mm minus material and water) passing through the bottom deck of the primary screen. This slurry is pumped to a 9-station EIW Autospec Classifier where the desired fractions are first discharged into twin 1117 mm x by 9.7 m long EIW dewatering screws underneath the classifier. Washed and dewatered concrete sand recovered by the screws is then stockpiled. Here again, tight control is exercised over the finished product gradation. Any excess sand and chip fractions are directed to a side process, known as the 6 mm leg, where they are separated by a Luff 5x16 screen into 6 mm stone and fill sand. (This operation also makes extensive use of Luff conveyor parts, including head pulleys, tail pulleys and rollers). A relatively recent requirement for concrete aggregate by the City of Winnipeg is blend of three sizes - the 20 mm x 5 mm coarse aggregate, 5 mm minus fine aggregate and also a 10 mm x 1.25 mm graded fraction. The latter is recovered from the secondary screen during the final sizing stage of the coarse aggregate.
     Like all aggregate producers, Inland faces the ongoing challenge of meeting market demand for a non-renewable resource, including a significant change to the Winnipeg aggregate business in the near future. Jones estimates that extraction at the CN pit will continue for two more years, when its reserves will be depleted. At that point, all production and suitable equipment will be relocated to the Pine Ridge operation some 7 km away.
     Inland Aggregates Ltd. is part of the North American Lehigh Group and worldwide Heidelberg Cement group.

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Canada's Top 20 Quarries

Click here to download pdf of Top 20 List (48k)

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Capital Paving
tackles demanding job

By Andy Bateman, Engineering Editor

      A tricky overpass paving job in southern Ontario this spring called for an innovative approach to materials delivery, paving and compaction. Ministry of Transportation of Ontario (MTO) contract 2001-3011 is valued at $28.7 million and provides major improvements to the intersection of Highways 7 and 8 in Kitchener, Ont. The contract's principal new structure is a two-lane flyover ramp that will eliminate an awkward crossover point for traffic transferring from Highway 7 westbound onto Highway 8 eastbound. After an April 2002 start, the contract is nearing completion, with hot mix asphalt paving on the flyover representing the last major challenge for paving subcontractor Capital Paving Inc.
     Jim Karageorgos, Capital's asphalt operations manager, reports that protection of the structure's deck waterproofing layer impacted on every aspect of the paving job, including material delivery, paving and compaction. "Our job here was to place a 40 mm lift of Heavy Duty Binder Course (HDBC) base asphalt and a 40 mm Dense Friction Course (DFC) surface lift on top of the structure's 10 mm thick deck waterproofing layer. Contract conditions stipulated that the waterproofing layer must be covered by the base asphalt within seven days of its installation. During that time, and especially during base paving, great care must be taken to protect the waterproofing layer as it can be damaged by excess heat or heavy equipment." Capital successfully completed the flyover paving over two nights, with the base lift completed on the first night and the surface lift the following night.
     Karageorgos explains the issues involved: "The waterproofing layer on the flyover deck consists of rubberized asphalt covered by asphalt core protection board. The boards are lapped shingle fashion, so paving must start where the waterproofing finishes to avoid catching any edges. During paving, heat from the base asphalt softens the waterproofing, with the area around the paver particularly susceptible to overheating from the mass of hot material in the paver screed. This is not normally an issue on a bridge deck because the waterproofing section is typically short and almost level. On this job however, the flyover design incorporates relatively steep grade and superelevation (cross fall) angles, with waterproofing over the entire 500 m length. It was therefore essential to keep the paver moving and so avoid the risk of local overheating. Had the paving operation been significantly interrupted for any reason, the paver could have started to sink into the softened waterproofing and lose traction. An equally undesirable situation could have arisen where whole sections of softened waterproofing start to move and slide. Good paver traction was a must as the paver was pushing a truck containing up to 40 tonnes of hot mix asphalt, in addition to the material in the screed and its own weight."
     Paving foremen John Gmeindl and Agostino Cabral were pleased and also somewhat relieved to see the successful completion of the critical base paving job. "At the planning stage, we considered paving the base asphalt with two pavers in echelon. That approach would have completed the job quickly, but it also meant increased risk of waterproofing layer damage if there were any production hiccups. Given the sensitivity of the waterproofing layer, we decided instead to cover the 12.5 m wide pavement in three single sections each just over 4 m in width. By using one paver at a time, we were able to keep tight control on material supply while minimizing heat and equipment loads on the waterproofing layer." Cooler night temperatures also helped the paving and compaction process, unlike daytime paving where the surface would be absorbing additional heat from the sun. At the supplying asphalt plant, night working meant one job and one mix, thereby avoiding the challenge of having to mix, store and load different mixes for other contracts. Hot mix asphalt was delivered to the job from Capital's Aberfoyle plant, with a fleet of seven 38-40 tonnes capacity live bottom trailers completing the 35 km haul to the jobsite. Flyover design was also a factor here as its 6 per cent superelevation ruled out the use of conventional end dump trucks and any other vehicles at risk of tipping. Trucks arriving on site fed material to Roadtec RP180-10 and Barber Greene 260B pavers. In this application, grade and slope were predetermined by the structure, allowing the paving crews to focus on correct mat thickness and longitudinal joint alignment.
     Behind the pavers, compaction began with a Caterpillar CB 534D dual steel drum breakdown compactor, although once again the process was adapted to suit the special nature of the job. Running in static mode only, the CB 534D stayed well back from the paver to avoid any risk of pushing or shoving the newly placed asphalt. As an added precaution, the operator monitored the surface temperature with an infrared temperature gun and only travelled on areas of the mat that had cooled to 120Á C or less. With the base asphalt still at about 150Á C just behind the screed, that often meant the CB 534D staying back 200 m or more from the paver. Later, a Caterpillar PS 360B pneumatic roller completed the base compaction job, while a small Wacker RD 11 unit finished off any detail work to edges and utilities.
     Once the base asphalt was completed, the paving of the surface lift was routine, as the base provided a protective travelling surface for trucks, equipment and service vehicles. Turning to materials and sources, asphalt cement for the HDBC and DFC mixes was supplied by Canadian Asphalt Industries. The Performance Grade Asphalt Cement (PGAC) utilised in both mixes was bumped to PGAC 70-28 to provide additional durability, representing two 6Á C grade bumps from the base level PGAC 58-28 specified for Zone 3 in Ontario.
     Aggregates for the HDBC mix included manufactured sand from Capital's own pit, together with 19 mm and 13.2 mm coarse aggregates from Lafarge Canada's Dundas quarry and Dufferin Aggregates' Flamborough quarry respectively. Lafarge Canada's Brockville quarry supplied both coarse and fine aggregates for the DFC mix.
     Capital Paving Inc. is headquartered in the Township of Puslinch near Aberfoyle, Ont. The general contractor on the 2001-3011 contract was Oakville, Ont.-based Dufferin Construction Co.

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Unique challenges
for Winnipeg Main Street

By Andy Bateman, Engineering Editor

     A concrete road reconstruction project in the centre of Winnipeg presented unique challenges to the city's roadbuilders, both in terms of construction and its impact on city life. Winnipeg's Main Street runs approximately north-south through the heart of the city centre and is flanked by the historic Exchange District to the west and the Theatre District to the east. This year's reconstruction of its four southbound lanes between the Disraeli Freeway and Portage Ave. will complement work done on the northbound lanes in 2001. In addition to full depth pavement reconstruction, work on the 900 m long stretch includes features such as new sidewalks with patterned paving stones, new trees, planters and "heritage style" street lighting. Eligible costs within the project's $3.6 million price tag are shared equally by all three levels of government, as the project is part of the Downtown Waterfront Canada Manitoba Infrastructure Program.
     For the city's Department of Public Works, the job involved dealing with unique construction challenges in addition to the social and economic impacts of a downtown construction zone. Fred Corey, DPW project manager, explains: "Main Street is about 100 years old and its original concrete structure has been repaired several times over that period. However, repairs have sometimes been expedient rather than effective, including the placement of a lift of concrete directly on top of old trolley (streetcar) rails. More recently that concrete lift was itself covered by asphalt overlays. Not surprisingly, this has not provided a stable base for today's heavy traffic, particularly around the rails where significant settlement has occurred. As a result, we decided to replace the whole pavement and remove all the old concrete and asphalt as well as the rails." Corey adds that concrete pavement design is common in the Winnipeg area due to poor ground conditions that include extensive clay deposits and silt lenses. These poor conditions are reflected in the design of the pavement's substantial cross-section - after excavation to subgrade, a layer of a geotextile is covered by a 600 mm lift of 150 mm minus crushed rock base. This granular base is followed by a 300 mm lift of 51 mm minus and a further 75 mm lift of 19 mm minus. Once compacted, these base materials receive a 250 mm thick lift of 32 MPa concrete, for a total pavement thickness of nearly 1230 mm.
     To minimize construction zone impacts, the Public Works Department sought public input through the Main Street Reconstruction Advisory Committee (RAC).
     As a result, several mitigation measures were implemented, including the division of the project into two eight-week construction periods. The first (south) phase extended from William Ave. to Portage Ave. and will be followed by the second phase from Alexander Ave. to William Ave.
     Winnipeg-based JC Paving Ltd. is the contractor for both phases of the road reconstruction, while Kodiak Construction, also of Winnipeg, has been responsible for associated water and land drainage sewer work.

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Poised for growth

An all-new asphalt plant set up in southwestern Ontario combines a strategic market location with the flexibility to travel when required.

By Andy Bateman, Engineering Editor

    Chatham, Ont.-based Seal-On Paving Ltd. recently commissioned a new portable hot mix asphalt plant in a purpose built yard just north of the village of Watford and about midway between London and Sarnia. Although this may not seem like a promising location for a new operation, Kim Chauvin, Seal-On's manager of operations, explains that it has a number of advantages: "The new operation provides good access to any work in the Highway 402 corridor and the growing community of Strathroy. In addition, it complements market coverage by our existing Chatham operation and has already helped Seal-On win supply contracts with Middlesex County and Lambton County. All that said, we also wanted the ability to move the plant and win work elsewhere if the opportunity arises in the future. This plant is fully portable and can be dismantled, moved and operating in a new location within seven days."
     The new portable plant, one of ADM's Roadbuilder Series, is a parallel flow design rated at 145 tonnes/h and was supplied complete with drying/mixing drum, cold feed bins and conveyor, silo system, asphalt tank and wet scrubber system. Chauvin reports that the plant set up went well, thanks to careful planning and strict adherence to the manufacturers set up drawings. "Before the plant arrived we checked and rechecked that items such as the silo foundations were correctly located. As a result, eight separate trailer loads were unloaded and positioned in a single day."
     In operation, a Caterpillar 950G wheel loader is used to charge the plant's four cold feed bins. Each bin has a struck capacity of 18 tonnes and equipped with a variable speed feeder to regulate material flow onto a 610 mm collecting conveyor. Feed material is then directed over a Syntron 3x8 scalping screen, initially fitted with a 38 mm square opening wire screen cloth to remove any oversize. From there, screened feed is conveyed to a chute fitted with a manual diverter gate to facilitate sample collection and feeder calibration. Material from the chute falls onto a separate conveyor and passes over a scale fitted with a 150-kg capacity platform load cell before entering the dryer drum. Once inside the 1.8 m diameter by 9.7 m long dryer, the cold feed is dried and heated by a Hauck StarJet 260 multi-fuel burner rated at 49,300,000 Btu/hr and fuelled by either natural gas or light diesel fuel. A collar on the drum enables recycle material (RAP) to be added to the mix, while finished product discharging from the drum is elevated by a 200 tonnes/h capacity drag conveyor into a 68-tonne capacity self-erecting product silo. The silo, mounted above grade to ensure adequate headroom for all trucks, is mounted over a 100-tonne capacity Active Scale Modu-Deck scale that has been sized to accommodate a 21.3 m long tractor trailer unit. Daily production from this set up is expected to average 2000-2200 tonnes.
     Exhaust gases on this plant pass through a venturi wet scrubber to remove particulate matter in the process air stream. The scrubber, mounted integral to the plant frame, has a 1.8 m by 3.6 m long barrel and utilises water from a purpose built closed circuit water system.
     In operation, a 51mm diameter ITT Flygt pump draws clean water from a nearby settling pond while discharge water from the scrubber is directed through a 152 mm diameter pipe into a grey water pond. There, fines in suspension settle out and clean water weirs back into the clean water pond through a duct connecting the two ponds. Each pond has a sloping concrete lined bottom, enabling accumulated solids to be removed as required by a wheeled loader. Water demand for this closed circuit system is minimal, with only make-up water needed to replace any lost in excavated fines or by evaporation.
     The plant's weatherproof motor control centre containing motor starters and circuit breaker protection is mounted on the main frame, while asphalt cement (A/C) is supplied from a 77 800-litre main tank or from two 9 725-litre reserve tanks. Diesel fuel for the burner is stored in a separate 58 350-litre tank.
     Environmental protection measures include a muffler to mitigate burner noise, although the nearest neighbour is an agricultural equipment dealership some 400 m distant. In addition, the new plant storm water management system includes an oil separator to prevent hydrocarbons from entering the surface water system. Infrastructure improvements to feed the new set up included a new 800 amp hydro line, a new natural gas line as well as a 200 mm water main with a 50 mm feed to the plant.
     The plant control room incorporates Asphalt Control System Inc.'s E-Z Blend controls with full batch tracking. According to its manufacturer, the E-Z Blend system can be field configured to simultaneously control up to two liquid asphalts, two recycled materials, twelve cold feed bins, multiple mineral fillers, baghouse fines, anti-strip, lime, rejuvenator and other materials. The software is specifically designed to easily perform "on-the-fly" sequential mix formula and/or tonnes/h changes, including fully coordinated starts and stops. The system's software handles up to 500 raw materials and 500 mix formulas, with virtually unlimited numbers optionally. A menu-driven method is used to manage necessary data, while both plant and system parameters can be changed using this menu system.
     Chauvin points out that the plant's bar code ticketing system enables remote access to the control centre to verify specific items such as mix type, mix quantity or truck identity. This system should reduce paperwork and errors while allowing authorized persons at the receiving site to verify all key shipment data with a laptop computer.
     Seal-On Paving Ltd. is a division of Seeley & Arnill Construction.

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Customized package warrants drill performance for St Marys Cement

A new drill rig has entered service for St Marys Cement under a unique maintenance and performance agreement.

By Andy Bateman, Engineering Editor

    Located on the shore of Lake Ontario 60 km east of Toronto, the Bowmanville quarry operation of St Mary's Cement typically produces some 3.8 million tonnes of calcitic limestone annually. About 85 per cent or 3.2 million tonnes of this total is utilised by the adjacent cement plant, while between 500 000 and 600 000 tonnes of quarry production is sold as aggregates by sister company CBM Aggregates. For mining manager Roney Almeida, these production requirements translate into daily production of some 10 000 tonnes/day for the cement plant and about 1500 tonnes/day for aggregates. These numbers in turn mean that some 1100 metres of blast hole drilling is required each week, equivalent to some 57 000 lineal metres per year.
     To tackle the blast hole drilling job, St Marys recently purchased a new crawler drill under an agreement that seeks to "continually maximize the availability, reliability and hence assist to maximize productivity and minimize costs of an Atlas Copco ROC L8 crawler drill at the St Marys Cement Company Bowmanville operations." According to Atlas Copco, this is the first such agreement for a surface mining application in Canada. Aimed at fostering a partnership between the parties and high owner satisfaction, the agreement warrants specific aspects of the unit's performance such as cost per metre, availability and productivity.
     When evaluating replacement machines, Almeida reviewed the performance of similar units already in service within the company, including three ROC L8's and two ROC L6 models in the company's Brazilian operations. Recognising that the Bowmanville drill would be operating in a much colder climate than the Brazilian units, Almeida also looked at a number of competitive units in similar Ontario applications. Manoeuvrability and tramming (travel) speed were additional factors, as material from each of Bowmanville's four benches is blended to meet the required chemical composition of the cement kiln feed. The benches vary considerably in height, with the 4 m high top bench overlying 2nd 3rd and 4th benches that are 22 m, 20 m and 10 m high respectively. The drilling application itself is straightforward in the evenly bedded limestone, with vertical blast holes and generally level drilling surfaces. The 134 mm diameter production blast holes are drilled on a typical pattern of 4.27 m x 4.88 m, burden and hole spacing, respectively, with one weekly blast producing an average of 50 000 to 60 000 tonnes.
     Subject to certain conditions, the agreement covers all critical aspects of the drill's operation and performance in this application. These include parts supply, technician support and drilling cost as well as availability and productivity.
     With respect to mechanical availability, the agreement sets out the supplier's commitment to availability targets that vary depending on the age of the machine. Machine productivity is also tracked, with both availability and productivity subject to bonus or penalty payments.
     Apart from the agreement, all the main specifications for the drill rig are similar to stock ROC L8 units. Standard equipment includes items such as the manufacturer's electronic hole depth/inclination instrument, while optional equipment fitted to this particular unit includes a central lubrication system and diesel driven engine pre-heater.
     St Mary's Cement Co. is part of Grupo Votorantim, said to be one of the largest business groups in Brazil. Company literature indicates that its companies are leaders or have large shares in all the markets in which they participate, such as cement production, cellulose, paper, aluminum, zinc, nickel, long steel, polypropylene bioriented films, chemical specialties and orange juice. It also has an important share in the financial sector through Banco Votorantim. The group has an active participation in the energy sector - both in the self- generation destined to supply its productive units, as well as in the public sector for which it distributes and markets electricity.

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July/August 2004 issue

Aggregates and Roadbuilding Magazine
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