A Concrete Solution for Crumbling Quebec expressway.

One of the largest exposed concrete hig way paving projects ever undertaken in Canada involves the reconstruction and repaving of a 10 km section of the 17.2 m wide northbound and southbound lanes of Quebec's Autoroute 13 with 100 000 m 3 of high durability concrete.

Autoroute 13 is a six-lane, limited access concrete expressway linking Montreal’s West Island region with Laval, Quebec’s second largest and fastest growing municipality.  It also serves as the primary route between Dorval and Mirabel, Montreal’s two international airports.

Rex Town & Country placer-spreader receives a load of ready-mix for placement ahead of the paver.

Built in the mid-1970s, the original concrete and asphalt overlay pavement on the heavily travelled Laval section of the ex-pressway between Pont Louis Bisson and Pont Vachon had deteriorated beyond the point where conventional repair techniques could be used. The only option for the Quebec Ministry of Transport (MTQ) was to completely rebuild the roadway and its foundation.   Two problems were identified as being among the most serious causes for the internal and external deterioration of the expressway. The first was an inadequate subgrade drainage system that exacerbated the effects of Quebec’s extreme freeze-thaw cycles. The other was that the original road design specified short and thin concrete slabs without dowel bars. Prior to 1994, the MTQ used slabs ranging from 200 to 225 mm thick for concrete pavements. In 1994, the transport ministry changed the design to utilize slabs 250 mm to 300 mm thick to improve surface durability and longevity.

The MTQ and its consultants on the Autoroute 13 contract, Montreal-based G³nivar-Tecsult Inc., developed a new 30-year lifespan road pavement design that features an elaborate drainage system, a 270 mm thick concrete pavement incorporating dowels and dowel baskets and concrete shoulders. The finished mainline concrete pavement has the same MTQ smoothness and rideability specs as new asphalt highway pavements in Quebec.

The MTQ divided the Autoroute 13 rehabilitation project into two contracts. The first contract was won by Asphalte J.L. Campeau Inc., Ste. Therese, in June 2000 for a low bid of $19.9 million. The contract called for the reconstruction of the three northbound lanes, shoulders and ramps. A subcontract for the supply and placement of the concrete as well as the fine grading of the granular base materials was subsequently awarded by the general contractor to Longueuil-based Demix Construction, a division of St. Lawrence Cement Inc.

Demix Construction completed work on its grading and paving subcontract during a 25-week period from July to November 2000.  The second general contract for the reconstruction of the three southbound lanes, shoulders and ramps was awarded by the MTQ in June 2001 to Demix Construction for its low bid tender of $21.2 million. Mainline concrete paving commenced in mid-summer and work is currently on schedule with an anticipated completion in October.

Major quantities on the two Autoroute 13 contracts total some 200 000 m 3 of earthmoving, 80 000 m 3 of recycled concrete and asphalt and 344 000 m 2 of 35 MPa concrete pavement. A small amount of blacktop paving is used for the entrance and exit lanes.

According to Demix Construction’s operations manager Jean-Maurice Forget, the two contracts are virtually identical in terms of heavy grading, drainage, recycling and paving requirements except for two major differences. The contract for the northbound lanes included a 2 km experimental section of continuously reinforced concrete pavement.   The use of some 850 tonnes of reinforcing steel allowed the elimination of expansion joints on this section of the expressway. Although the concept is an accepted technique in the U.S. and Europe, this is the first time that it has been used in Canada.   Provincial highway officials will monitor the performance of the reinforced slab to see if the slightly more expensive method warrants use on future MTQ expressway projects.

The other major change between the two contracts was that the northbound lanes were paved on a 100 mm thick open graded drainage layer (OGDL) of lean concrete mix while the southbound lanes are being paved directly on the subgrade.

Containing 20 mm-5 mm aggregates, 90 kg/m 3 of Type 10 cement and a small quantity of water, the OGDL drains water away from underneath the pavement slabs to the subgrade collection system. This helps prevent water from pumping through the concrete pavement joints and eventually degrading the roadway structure. The OGDL also provided a smooth, level surface to receive the concrete pavement. Approximately 15 000 m 3 of permeable concrete was used.

Forget states that many of the valuable lessons learned during last year’s construction program have been used to plan and carry out the current contract. Also, as the general contractor, Demix site personnel are in control of scheduling all phases of the project – a much improved situation over last year when, as a subcontractor, Demix’s paving crews experienced numerous delays.

Design features

The new road profile for both the north and southbound lanes comprises a 150 mm thick layer of 19-0 mm crushed subbase materials compacted to 98 per cent Proctor and followed by a 500 mm base of 112 mm-0 mm recycled asphalt and concrete compacted to 95-98 per cent Proctor. Adjoining concrete slabs in the surface pavement are connected with 35 mm diameter x 450 mm long epoxy-coated dowels embedded in the slab edges at 300 mm intervals. The dowel baskets are positioned on grade every 5 m at the panel expansion joints.

The shoulders are built to the same specs as the driving lanes in the event that one or more extra driving lanes might be required in the future. The concrete shoulders also help maintain a tight joint with the driving lanes to prevent water infiltration. In the past, the MTQ has found it difficult to keep the joints between the concrete driving lanes and asphalt shoulders effectively sealed.

Mix design

The basic mix design for the 40 mm (±10 mm) slump concrete slabs consists of 40 mm coarse aggregates and 325 kg/m 3 of St. Lawrence Cement’s new TerC 3 ternary blended silica fume/fly ash cement. The TerC 3 cement being used for the Autoroute 13 project contains 20 per cent fly ash and 8 per cent silica fume.

TerC 3 cement is the result of an intensive research and testing program undertaken by SLC to develop a premium quality cement that would reduce alkali-aggregate reactivity (AAR) while producing a durable, long lifespan concrete. According to Jean-Maurice Forget, the TerC 3 mix offers excellent workability and controls edge slump better than other mixes. Admixtures in the mix included Eucon DX (water reducer), Airex L (air entrainer), and Eucon 727 (re-tarder), all manufactured by Euclid Admixture Canada Inc. The mix design has a flex strength of 4.5 MPa at 28 days.

All of the concrete for the project is produced on-site by Demix using a 120 m 3 /h capacity Johnson-Ross Unirover 1048 portable ready mix batch plant. The plant is turning out a 6 m 3 batch every three minutes.  Concrete slump and air content is checked frequently prior to the batch being released for shipment. A fleet of seven to 12 tandem dump trucks and 10-wheel trailers are hauling the concrete from the batch plant to the paving site.

Slipform paving

Demix mobilized three concrete slipform pavers to handle the mainline and shoulder paving operations. The main paving train features a Gomaco GHP-2800, a Rex Town & Country placer-spreader and a Gomaco T/C 600 texture cure machine. Operating at a width of 7.3 m, the two-track GHP-2800 forms the 3.65 m right and centre lanes (Lanes 1 and 2) in a single pass. The Rex placer-spreader, equipped with a 1219 mm wide, side-mounted placement belt that is raised and lowed hydraulically to allow haul truck clearance, is employed because the trucks are restricted from dumping directly in front of the paver.

The 3.65 m left lane and 3.30 m left shoulder (Lanes 3 and 4) are slipformed by a Rex Town & Country paver operating at a width of 6.9 m. The Rex is teamed with a CMI MTP-4004 material transfer placer and a Rex 2600 texture cure unit. Both the Gomaco and the Rex texture cure machines achieve the longitudinal texture by dragging a strip of Astroturf while tines on a rear-mounted traveller give the concrete pavement its deeper transversal grooved texture to prevent hydroplaning. After the texturing operations are completed, the machines apply Planicure 65, a white pigmented, water-borne curing compound manufactured by MAPEI Inc. The product is delivered to the site in 1000-litre capacity recyclable plastic containers.

The third slipform paver on the project, a CMI Super 200, is used to construct the 3.18 m wide right hand shoulder (Lane 5) with integrated concrete curb. It is teamed with the CMI MTP-4004 material transfer placer. The curing agent and texturing for the shoulders was done by hand. 

Sawed and sealed joints are made every 5 m in the pavement to approximately a third of the slab thickness. This operation was carried out during the initial setting period.

A new Ingersoll-Rand ABG Titan 325 paver was used to lay the OGDL. The paver’s dual tamper bar arrangement allowed Demix to achieve compaction without putting vibratory rollers on the concrete. The objective was to achieve stability within the drainage base layer without meeting a specific compaction density requirement.

All of the fine grading and concrete paving work is done off the same stringline to ensure grade and slope accuracy.

While the production cycle varies according to the weather and advance work by other sub-contractors, Demix crews are making steady progress. Demix’s site engineer Jean-Fran­ois Berthiaume told Aggregates & Roadbuilding that production ranges from 65 m 3 to 100 m 3 /h on mainline paving and 40 m 3 /h to 50 m 3 /h on the shoulder work.  The targeted production rate is 6000 m 3 per week on a 24/6 schedule.

Quality control

Demix has implemented a comprehensive quality assurance/quality control program to insure the new pavement performs as designed. The procedures include taking continuous test samples of concrete at the paver as well as regularly comparing the slab thickness with the amount of concrete being used to determine in-place accuracy.  A profilograph is used during the course of the project to obtain smoothness readings of the finished surface.

Aggregates and Roadbuilding Contractor
4999 St Catherine Street West. Suite 315
Westmount, Quebec H3Z 1T3
Tel: (514) 4879868 Fax: (514) 4879276
EMail: rocktoroad@sympatico.ca

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