Road Talk

A Runaway Success

This summer, MTO conducted a live demonstration of its new state-of-the-art runaway truck ramp on Thibeault Hill where Highway 11 descends into a busy commercial area of North Bay. Approximately 30,000 cars travel through the intersection at the base of the hill daily, making it one of Northern Ontario’s busiest intersections.

Opened to traffic in December 2008, the new dragnet system replaced a gravel bed arrestor on Thibeault Hill. The new system is based on the technology used to stop airplanes landing on aircraft carriers and consists of seven metal cable nets attached to energy absorbing canisters anchored in concrete barrier walls.

A 61 m spool of 1 mm thick steel alloy tape approximately 40 mm wide is enclosed within the canister. The tape is connected to the net and is pulled from the canister when the net is struck by a vehicle. As the tape is pulled, it passes around a series of 4 pins that are offset and located where the tape exits the canister. As the tape winds through these pins, it creates friction and dissipates the energy of the vehicle that is pulling the tape. For a large, heavy vehicle traveling at highway speeds, it is expected that tapes in the first few canisters will be pulled out completely. After winding through the pins, the stainless ribbons are slightly deformed and extremely hot due to the drag created by the offset pins.

The first net has one canister per side. The second net has two canisters per side and the remaining five nets have three per side. Each canister takes 20 kN (4,500 lbs.) of force to pull the steel tape. More canisters equals more resistance, increasing the stopping power of the net however, the force exerted upon a truck entering the dragnet system is only about 0.6 g – less than what you would experience from a hard, quick stop. Since the resistance of the canisters are designed for a fully loaded truck, lighter passenger vehicles entering the system would experience a much harsher collision than a fully loaded transport truck. By installing fewer canisters on the first two nets, the impact to lighter vehicles has been minimized.

On June 25th, 2009, MTO used a loaded tractor trailer and simulated a brake failure as it descended the hill. A 2004 international tractor with a six axle flatbed aluminum trailer was loaded with almost 60,000 kg, just under the legal gross weight of 60,100 kg and was driven into the runaway truck ramp at 90 km/h. To ensure the truck’s brakes were not used, a professional stunt driver was hired.

As the truck entered the ramp, the nets and canisters worked as expected. Rolls of steel alloy tape from the energy absorbing canisters were pulled through the offset pins and converted the truck’s momentum into heat and slowing it at a rate of 0.4 g – less than a hard stop. However, after the truck passed through gates 2, 3 and 4 the truck pulled to the right increasing the g force to 1.0 upon impact with the barrier wall near the end of the stop. Although dramatic, the 60 tonne truck experienced a controlled stop in less than 61 m and within five seconds. More importantly, the driver was able to walk away from the incident uninjured and the trailer load remained in place and intact.

A review of the demonstration found that the dragnet system performed as expected with both the nets and the barrier wall acting to contain the truck within the ramp. The steel alloy tapes became twisted and deformed as designed and the truck stopped at the distance and time predicted.

The demonstration is part of a broader MTO campaign to educate and encourage commercial vehicle drivers to use the runaway truck ramp in the event of brake failure. A stakeholder film is being produced to reach drivers who were not able to view the demonstration in person or via the project webcast.

MTO also provided interviews and film clips to the Discovery Channel to highlight this innovative engineering project on the Daily Planet program and worked with Cogeco Cable to develop a feature program on the demonstration.

For more information on the demonstration, please visit the project website at www.highway11northbay.com or contact:

• Jim Bucci Senior Project Engineer, Ministry of Transportation, 705-497-5450 or Gordan Rennie Regional Issues Advisor, Ministry of Transportation, (705) 497-5264.
• Please refer to the previous article, State-of-the-Art Technology for Highway 11 Runaway Truck Ramp, published in spring 2009, for more information on the exact assembly of the ramp system.

To see the final runaway truck ramp click here: Run-Away Ramp on Dicovery Channels Daily Planet

Video courtesy of Discovery Channel with permission

Road with a View: MTO's Installation of Transparent Noise Barriers

Figure 1 - Retention of commercial visibility through reduced visual height of barriers on QEW near Fort Erie

Figure 2 - Improved aesthetics along the QEW as it travels through a primarily residential section of St. Catharines.

In April 2007, the Ministry of Transportation awarded its largest ever capital contract investing over $167 million dollars (CAD) to widen the Queen Elizabeth Expressway (QEW) to 6 lanes through St. Catharines. Along with the road work, the project has 26,000 m2 of noise barriers that include 3,000 m2 of transparent window panes in specific locations. Extending from the Henley Bridge to west of the Garden City Skyway, the transparent sections of the barrier improve highway aesthetics through the city and decrease noise levels for residences and businesses.

In this highly developed area, the transparent noise barriers are well worth their premium cost since they allow more light to enter properties, continue to provide adjacent businesses with exposure and provide a sense of open space. As of September 2009, construction of the barriers through St. Catharines is over 50 percent complete.

Lightweight sound absorptive panels are stacked between steel ‘H’ posts to form the noise barrier. Additional design considerations were required to strategically place the reflective and absorptive panels in a manner to reduce noise reflected between the parallel barriers on the highway.

The transparent element is made from a composite plastic product that is sound reflective and placed at the top of the barrier within the posts like a window. Unlike the windows in your home, the plastic product is self cleaning. The glazing material on the composite plastic is so smooth that dirt and grime will not stick to it. The transparent barriers in Fort Erie have been in place for three winters and have never required cleaning.

Our transparent trend continues – MTO has announced further construction of transparent noise barriers along Highway 401 and Highway 3 in Windsor this fall.

To ensure the composite plastic windows could withstand climate and weather conditions advance testing was performed and included weatherometer, freeze thaw, anti-fracturing and ultraviolet tests. Their suitability was confirmed and transparent noise barriers are now an essential tool in MTO’s catalogue of less intrusive noise barriers.

For more information, please contact:

• Chris Blaney, Planning and Environmental Office, at chris.blaney@ontario.ca, or (416) 235-5561.

After the Rain: New Application for Compost from Canadian Landfills

Figure 1 – Compost Biofilter installed in the ditch on the East Side of Highway 8 near Cameo Drive, Kitchener, Ontario. Holding the survey rod is Karen Finney, a University of Guelph graduate student who led this research project.

In the summer of 2007, MTO partnered with the University of Guelph on a research project to improve source water quality. With the assistance of Toronto and the Regional Conservation Authority, Ontario Centres of Excellence, Alltreat Farms, Region of Waterloo, Region of Peel and Filtrexx Canada, the University of Guelph installed automatic water samplers and water level sensors for monitoring flow rate and water quality on the east side of Highway 8 near Cameo Drive in Kitchener, Ontario. These monitors are in place to evaluate biofilters, a new water filtration system for urban stormwater runoff, which are anticipated to have significant environmental and economic benefit.

A relatively new innovation, biofilters are made from a mesh photodegradable tubular sock filled with a filter material made of inexpensive, surplus, natural non-hazardous waste from compost production (i.e. coarser compost material remaining on the 1.27cm (0.5”) sieve). Compost has the natural ability to absorb heavy metals, oil and grease, and to break down contaminants making it a natural, organic filter. Preliminary research of biofilters as an effective treatment for stormwater shows promise as they are expected to reduce levels of zinc, copper and petroleum hydrocarbons in runoff.

During a rainstorm, pollutants from tire wear, engine oil leaks, break pad wear, metal rust, car fumes and atmospheric deposition which have settled onto pavement surfaces combine with stormwater runoff reducing its quality. Compared to natural areas, runoff from impervious roads has increased pollutant loads that can be harmful to birds, humans, plants and aquatic life.

Traditional stormwater management has concentrated on flood prevention with little focus on contamination removal. Recently, the heavy metal pollutants from automobiles and their toxicity to the natural environment have been of particular interest. While grass swales, vegetative buffers, concrete riprap, silt fences, and straw bales are common treatments to filter out most solid pollutants and particles, biofilters are able to remove particulate contaminants and have the added advantage of creating a permeable dam to promote settling ponds upstream.

Based on studies in Sweden and the USA, key factors that influence the concentrations of urban water contaminants include: annual average daily traffic, antecedent dry days and total event rainfall depth. Information on these parameters is required to calculate the biofilter size for a given site. Biofilters must be designed large enough to manage flow-through capacity as well as reduce contaminant concentrations.

The Kitchener site was categorized as a medium-sized catchment area because of its medium to high average annual traffic rate of 23,000 vehicles per day over four lanes. Installation was performed by Filtrexx Canada and was completed in July 2007. After its installation, an ISCO 3700 portable flow-weighted sampler collected runoff samples upstream and downstream for 20 monitored storm events over 2007 and 2008.

Preliminary results of the outlet runoff samples are promising. The Ontario Provincial Water Quality Objective (PWQO) has minimal acceptable levels for various contaminants such as total suspended solids, zinc, and copper. Before filtration at the Highway 8 site, runoff contaminant levels exceeded the minimum standard guidelines. Samples after filtration showed a significant improvement in quality to within minimum acceptable PWQO standards – total suspended solids levels were reduced by half; and both zinc levels and polycyclic aromatic hydrocarbons were reduced by a third. Though post filter copper levels are not yet below the minimum, they have been reduced by 29 percent. A second biofilter installed downstream reduces copper levels to below the PWQO minimum level.

There are many existing urban stormwater management technologies which stabilize and filter out contaminants, but often these do not meet the provincial water quality guidelines. With proper design, compost biofilters, when used alone, or in combination with other stormwater management systems, are a cost effective treatment that will continue to improve runoff water quality.

For more information, please contact:

• Nick Close Principal Landscape Architect, Design Standards Section at Nick.Close@ontario.ca, or at 905-704-2229

• OR

• Bahram Gharabaghi, Ph.D., P.Eng, Associate Professor, Water Resources Engineering, University of Guelph, Guelph, Ontario, at bgharaba@uoguelph.ca, or at 519-824-4120 Ext: 58451

Moving Forward Together
New consistent approach to Materials Acceptance Testing

At the MTO laboratory in Downsview, ministry staff monitor the equipment and test set-up used to evaluate the air void system (AVS) parameters of hardened concrete. The same test is done in commercial laboratories that perform acceptance testing on concrete for MTO contracts. This is one of the tests that will change from being a QC test (performed by the contractor or a laboratory working for the contractor) to a QA test (performed by a laboratory working for the ministry).

As part of a modernized approach to contract delivery and oversight, the Ministry of Transportation is revising the acceptance approach for all highway engineering materials. In doing so, the ministry intends to implement a common acceptance framework across material areas. It is expected this will result in more efficient specifications, and less onerous administration.

Materials acceptance testing is how the ministry determines whether materials such as concrete, soils, asphalt and aggregates are acceptable for use in highway construction projects. With this initiative, materials will be tested for acceptance by either independent testing laboratories retained by the ministry or, in some specialized cases, by the ministry’s own laboratory.

The current system includes a variety of approaches to acceptance testing: contractor’s Quality Control (QC), owner Quality Assurance (QA), or a combination of these. Referee testing is not applied uniformly or with a consistent philosophy. An overall lack of consistency regarding acceptance testing has created difficulty understanding specifications and led to delays in field decisions, and possibly mistakes. A lack of consistency also creates challenges for development of new specifications and initiatives such as performance based acceptance.

In examining the existing systems, several areas were identified for improvement. Consistent payment methodologies across material areas were required to clarify and improve the administration of specifications. More efficient QC requirements were needed to foster contractor innovation and focus on priority areas, optimizing contract administration resources and reducing costs. In addition, MTO recognized that payment systems needed improvements to ensure they were fair, transparent and defendable from a public trust perspective.

Together with industry partners, MTO has developed a uniform set of principles that will guide specification development in each material area. These principles are:

1. QC testing is the responsibility of the contractor.
   The ministry will not specify requirements for QC activities, and existing mandatory QC testing will be eliminated. In some cases were appropriate this will be accomplished through a phased approach. Contractor QC test results will not be submitted to the ministry. Contractors will continue to be responsible for the sampling of materials and delivery to the designated QA laboratory for owner testing.
2. Material acceptance is based on QA test results.
   QA testing will be conducted by independent laboratories, retained by owner, or where necessary conducted by the owner. A lot/sublot system will be applied to all material received to ensure that all material has an equal chance of being sampled. QA test results will be provided to the contractor in a timely fashion.
3. Referee testing will be used for dispute resolution for all materials.
   All materials will have a binding referee process for the purpose of resolving material acceptance issues. This process can be invoked by the contractor without pre-condition.
4. Personnel and labs will be appropriately qualified.
   The ministry will continue to operate correlation programs for QA and referee laboratories, and will continue to monitor capacity and performance of the same. MTO will continue to require appropriate industry certifications (e.g. Canadian Council of Independent Laboratories, Canadian Standards Association) for QA and referee labs and their staff. QC labs will be encouraged to participate in both correlation and certification programs.

Using a harmonized set of principles as the basis for materials acceptance testing will improve consistency, while recognizing the expertise of industry partners to establish and implement QC processes.

Over the summer of 2009, the committee completed the Terms of Reference to guide the individual material workgroups with the specification development. The ministry and its industry partners have identified the areas of priority and developed an implementation plan to make the necessary modifications to the specifications to introduce this initiative. Changes will be phased in gradually as specifications are revised.

Three internal task groups, with representatives from regional and head offices, have been established, one for each major material area: Bituminous, Concrete, and Soils and Aggregates. Industry is similarly represented by groups such as the Ontario Road Builders Association (ORBA), Ontario Hot Mix Producers Association (OHMPA), Ready Mixed Concrete Association of Ontario (RMCAO), and the Ontario Stone, Sand and Gravel Association (OSSGA). These three groups will review and finalize the changes to the specifications in line with the established principles.

To ensure these changes occur over a reasonable time period, certain items will be considered out of scope, including:

• technical changes to specifications;
• modifications to acceptance parameters and limits;
• changes to bonus and penalty; and
• review of test data.

With a documented set of principles for material acceptance, MTO intends to have specifications across all material areas, for use now and in the future, that follow a consistent set of acceptance principles based on QA testing. These specifications will be intuitive in their interpretation, transparent in their approach and efficient to administer.

• For information, contact Tony Tuinstra, Head, Construction Contracts Section, at (905) 704-2197 or at Tony.Tuinstra@ontario.ca.

Just a One-night Stand: QEW Martindale Bridge Demolition and Contractor-proposed EA addendum

Demolition of the old Martindale overpass underway, as viewed from the west side of the overpass where the new structure remains scaffolded.

Viewed from the east side of the Martindale overpass, four hydraulic excavators have demolished most of the old structure, revealing the new bridge immediately behind it.

The Queen Elizabeth Expressway (QEW) is a major Ontario expressway connecting the economic powerhouse of the Greater Toronto Area to Niagara/U.S.A. border crossings, with consequent high traffic volumes. Accordingly, the Ministry of Transportation of Ontario (MTO) strives to keep it open at all times, particularly through the City of St. Catharines - the only four-lane stretch of QEW remaining between Toronto and Niagara Falls. MTO however made an exception during its recent construction project to expand the QEW to six lanes through the city and agreed to the first complete closure and diversion of the highway to accommodate the overnight demolition of the Martindale overpass.

A full closure of the QEW was not part of the initial design. Plans originally called for one-night single lane detours in each direction with the sole purpose of keeping the QEW open for a 10 hour period during bridge demolition. This traffic management approach had been successful in keeping the QEW open during removal of the Lake Street Bridge in St. Catharines 10 months earlier. However, the Martindale worksite was very narrow – more constricted than Lake Street, and presented concerns with safety. Allowing a full closure in both directions precluded the construction of the single lane detours and produced a significant cost saving by avoiding the throwaway use of 5,420 tonnes of Granular 'A', 1,400 tonnes of temporary SP19 Hotmix, and 7,600m2 of Tack Coat. Additional savings were achieved by deleting the need for the placement/relocation of temporary concrete barrier plus its removal. The full closure was also estimated to cut approximately four weeks from the construction schedule. In accordance with the contract conditions, the resultant savings were shared equally between the contractor and the ministry.

With such clear benefits, Dufferin Construction approached MTO early in March 2009 with the change proposal for a full closure. Accepting a full closure would require a Transportation Environmental Study Report (TESR) addendum in short order. While such addenda are typical at planning stages, it is unusual for them to be driven by construction. Ministry personnel agreed with the merits of the proposal and worked closely with Dufferin and their consultant to get an approved addendum within the tight timeframe. The TESR addendum was advertised in early August and approval was received in early September after a seamless process and without bump-up. Both the City of St. Catharines and Region of Niagara were very supportive of the change in plans.

The QEW was closed promptly at midnight, October 17, 2009, in both directions between Ontario Street and Highway 406. Once the full closure was in effect, heavy machinery moved in swiftly to remove concrete barriers and spread a thick layer of gravel over the roadway to protect it from falling debris. By 12:50 a.m., hydraulic excavation equipment began to tear apart the old structure, carefully orchestrated to avoid damaging the new Martindale overpass, built less than 1 m apart from the old structure. Over one hundred interested spectators from the community were present at the onset of demolition, but dwindled to a few dozen by 2:30 a.m. when the majority of the structure was down. Spectators were respectful of contract limits and stayed behind fencing while watching the contractor’s team of 16 demolish the old structure. Traffic was fully restored by 9:45 a.m. Sunday, about 15 minutes ahead of schedule.

OPP and Niagara Regional Police reports indicate that vehicles detoured without incident or traffic backups during the closure. Permanent changeable message signs notified motorists of the closure, starting eight days beforehand. Niagara-bound traffic was diverted at Highway 406, to Highway 58, then back to the QEW at Thorold Stone Road. Toronto-bound traffic was detoured at Ontario Street along local streets before rejoining the QEW at Highway 406. The closure was coordinated with the Ontario Provincial Police and Niagara Regional Police. Advance notice was comprehensive and included area television stations and papers, the Weather Network, area fire departments and other emergency agencies, local churches, tourist information centres, border crossings and agencies, and the Ontario Trucking Association.

Construction of the Martindale structure continues, as the east half of the overpass remains to be built. Some of the scaffolding on the west structure has already been shed to reveal a distinctive, bas relief wave pattern on the parapet wall that mirrors detailing on the centreline ship prow sculptures at either end of the historic Henley bridges. The new Martindale overpass has no central pier and spans the entire roadway as one long elegant arch. Once completed, the new Martindale overpass will frame the Henley bridges in a gateway effect when approached from the Niagara-bound direction.

Listen to Calvin Curtis, Area Contracts Engineer on the QEW widening through St. Catharines, in an interview live at the demolition about 1:00 a.m., October 18, 2009. Calvin explains detour arrangements in Interview 1 (1:26 min) and the change proposal for closure in Interview 2 (2:09 min). Short video clips of the demolition in progress are also available for viewing.

For more information, please contact:

Calvin Curtis, Area Contracts Engineer, Central Region Contracts Office, at

Calvin.Curtis@ontario.ca, or (416) 235-5442.

Turning Back Time: Successful Mitigation of Reinforcing Steel Corrosion in Bridges through Electrochemical Chloride Extraction

The Burlington Skyway Bridge

Like many jurisdictions, Ontario relies on constant innovation to maintain our highway infrastructure. In 1989, Ontario was the first jurisdiction in North America to use electrochemical chloride extraction (ECE) to arrest steel corrosion and to mitigate the resultant effect on concrete. ECE was applied on an experimental basis to pier S19 of the Burlington Bay Skyway Bridge, and has since been successfully used on several MTO structures both in the Greater Toronto and North Bay areas. Based on the ECE applications to date, testing over the last 20 years has provided evidence of the technology’s effectiveness in stabilizing the condition of steel reinforcing bars suffering from corrosion.

A non-destructive rehabilitation technique, ECE can extend the life cycle of reinforced concrete bridge elements that have been compromised by electrochemical corrosion caused by de-icing salts, or carbonation. Over time, the natural protection provided to the steel by concrete is breached by the ingress of chloride ions from winter de-icing applications. Once a sufficient quantity of the chloride ions reach the reinforcing steel, it will corrode and expand causing the concrete to crack and spall resulting in costly repairs or replacement.

Concrete has a high pH value (between 12 – 14) due to its chemical/hydroxyl ions (mainly calcium and potassium). In this high pH environment the passive oxide film around the reinforcing steel is stable and corrosion cannot occur. However when the pH balance of the concrete is reduced below approximately 9.5, the oxide film is no longer passive and if left untreated, can result in corrosion followed by increased rehabilitation costs and reduced structure service life.

The ECE process removes chloride ions from contaminated concrete and increases the concrete pH value around the reinforcing steel through ion migration. Similar to cathodic protection, the process uses a direct electrical current that moves chloride ions away from the reinforcing steel rendering it passive. The current applied during the ECE process is approximately 100 times the current used in conventional cathodic protection, but it is applied for only a short time. A temporary anode is installed on the surface of the concrete for six to eight weeks, with a direct current flowing between it and the steel reinforcement which serves as the cathode. A continuous flow of current must be maintained to have the negative chloride ions migrate away from the steel toward the temporary positive anode and the concrete surface. The electrolytic production of hydroxyl ions at the reinforcing steel surface also results in a higher pH around the steel. When the rehabilitation process is terminated and the external anode is removed, the reinforcing steel is in a chloride-free, highly alkaline concrete. The result is a strong re-passivation of the embedded reinforcing steel, halting further corrosion.

Over an evaluation period of 20 years, the reinforcement corrosion potential readings at S19 remained passive as did the corrosion current rates indicating that significant long-term passivation of the steel reinforcement can be achieved by the ECE treatment. Although it has a high initial cost, MTO will be conducting further life-cycle cost analysis on ECE to determine whether its use can be increased and considered on a more routine basis.

For more information, please contact:

Frank Pianca at (416) 235-4691 or Frank.Piance@ontario.ca.

Improving Through Trial and Error: Precast Concrete Slab Repair Technology

Figure 1. Use of jack-hammer to remove concrete in dowel slots.

Figure 2. Failure occurred in the dowel slots in the adjacent slab.

Figure 3. Six continuous slabs placed November 2004.

Figure 4. The same six continuous slabs in October 2009.

Highway 427 is a major urban freeway carrying an average of 333,000 vehicles per day north and south through the City of Toronto. Rehabilitation of this concrete pavement was challenging due to the limited time frame for traffic closures and the necessity of this link to Ontario and Toronto’s transportation network. In 2004, the ministry recognized that conventional repair methods would result in extended closures and significantly limited the quality and rate of production/completion of the work. Although precast concrete was an emerging technology in 2004, MTO analysed the application and performed the first trial in Canada of three precast concrete pavement slab repair methods. In 2005, less than a year after the trial began, Road Talk reported on the results (for details, see the article published in the Summer 2005 edition of Road Talk, “Pre-cast Repairs Show Potential” http://www.mto.gov.on.ca/english/transtek/roadtalk/rt11-2/#a2 ). Now, after nearly five years of monitoring, the ministry is finding some unexpected yet educational results.

Precast concrete slab repairs are an alternative to fast-track concrete mixes, which can be temperamental with questionable long term durability. Precast slabs are constructed offsite in a controlled environment allowing better concrete quality and curing conditions. In addition, there are minimal weather restrictions on placement, and a reduced waiting time prior to opening to traffic.

Three different precast concrete pavement repair methods were evaluated: the Michigan Method, the Fort Miller Super-SlabTM Intermittent Method, and the Fort Miller Continuous Super-SlabTM Method. The methods differ in how the underlying base course is prepared and how the precast slabs are installed and dowelled into the adjacent concrete.

Since 2004, the performance of these trial slabs has been monitored annually. Some of the slabs were damaged and required removal. In particular, the Michigan Method slabs that were installed by cutting dowel slots into the existing adjacent concrete were susceptible to failure in the dowel slots. During construction, over-cutting and the use of jack-hammers to remove concrete in the slots damaged the existing adjacent concrete. Although the new precast slabs performed well, the failures occurred in the dowel slots that connected the precast panels to the existing concrete (see Figures 1 and 2). To address this issue, MTO revised the specification to require the use of a gang-saw to cut the slots and lightweight chipping hammers to remove the concrete.

The Fort Miller precast slabs performed the best, and both the intermittent and continuous repairs have been incorporated into recent Highway 427 contracts. Figure 3 shows the six continuous slabs when they were placed in November 2004, and Figure 4 shows the same six slabs 5 years later, in October 2009.

Several important lessons have been learned from the Highway 427 precast trials. The ministry has determined that sawcutting the removal area is a critical step because the slabs are cast to an accuracy of millimetres and the removal area must allow the slab to fit tightly. In addition, the surrounding concrete must not be damaged during sawcutting, removal or placement of the precast slab; if it is damaged, the precast slab will be surrounded by failed concrete. Base preparation is also key to the success of the precast slab, and therefore precision grading equipment is specified to ensure a uniform platform on which to place the precast slabs.

Precast concrete pavement slabs have been used recently on two additional contracts on Highway 427—southbound in 2008 and northbound in 2009. With the new data gathered in past and recent trials, the Ministry of Transportation continues to be leaders in the development of accelerated concrete pavement repairs.

For more information, please contact:

Becca Lane at (416) 235-3732 or Becca.lane@ontario.ca.

Waste Not; Want Not: Optimizing the Use of Reclaimed Asphalt Pavement in Ontario’s Flexible Pavements

Typical Performance of a Recycled Pavement Section

MTO recognizes the importance of maintaining a sustainable environment and respects the need to conserve non renewable resources. The MTO recycling policy that specifies the use of Reclaimed Asphalt Pavement (RAP) content in Hot Mix Asphalt (HMA) was recently reviewed and updated. The review came on the heels of the successful completion of a demonstration contract constructed in 1999 using Hot In-place Recycling (HIR) and Recycled Hot Mix (RHM). The demonstration showed that premium surface courses required for freeways perform equally well with or without RAP in the HMA. The results of this demonstration, as well as the encouraging results of a state agency recycling policy survey, lead to the update of MTO’s environmentally sustainable construction program policy.

Pavement Recycling = Energy Savings + Sustainability

RAP has gone from being a waste product in the 1970’s to being a valuable recycled material used by transportation agencies in pavements. The Ministry’s first use of RHM occurred in 1979; by 1986, 45 percent of the Ministry’s annual placement of hot mix was RHM.

Asphalt pavement is the most recycled material in North America. Although there are many ways to make pavement more sustainable, asphalt recycling is one of the most popular choices and can normally be used with other strategies to maximize the sustainability of a project. Recycling allows for the reuse of valuable aggregates and asphalt cement, can also reduce green-house gas emissions, and save energy, contributing to sustainability. Besides using RAP to produce RHM, the Ministry has used other recycling technologies including Hot In-Place Recycling (HIR), Cold In-Place Recycling (CIR), Cold In-Place Recycling with Expanded Asphalt Material (CIREAM), Full Depth Reclamation (FDR), and FDR with Expanded Asphalt Stabilization (EAS) which minimize transportation-related expenses and pollution because the raw material is close at hand.

Early RAP Restriction

The Ministry was interested in reviewing the policy prohibiting recycled material in the surface of premium mixes. Earlier MTO specifications permitted up to 40 percent RAP in binder courses on lightly travelled roads. On the higher volume roads, RAP was permitted only in binder courses at least 150 mm from the pavement surface. Generally, a maximum of 20 percent RAP was allowed in surface courses; however, no RAP was permitted on roads in the heaviest traffic category, or in premium mixes, limiting RAP use to surface courses and binder courses on roadways with 2500 or less Average Annual Daily Traffic (AADT) per lane. This restriction meant that aggregates for premium mixes, which must go through a pre-approval process, could not be recycled back into surface courses placed on high volume freeways. This restriction was meant to minimize the risks associated with variability of the material and to ensure that the aggregates provided sufficient friction.

Trial Demonstration and Findings

In response to a call for more sustainable and environmentally friendly pavement construction, in 1999 the Ministry constructed several trials on one of Ontario’s busiest highways - Highway 401 east of London, to investigate the impact recycled content would have on material properties under heavy traffic volumes. The Ministry wanted to explore the use of RHM; compare pavement rehabilitation techniques (specifically HIR) with a single course of standard HMA; and evaluate the use of RAP in the pavement surface. The project was designed to produce pavements that would be sustainable – i.e. efficient and environmentally friendly without compromising long term performance.

Due to construction defects, the new Dense Friction Course (DFC) control section did not perform as well as expected. Poor construction effectively shortened the life expectancy of the control section from the predicted 12 years to 8 to 9 years. The section exhibited end-load segregation throughout. The new DFC was outperformed by two of the recycled sections, the RHM and one of the HIR sections which had performed especially well. Although none of the recycled sections have met the 12-year life expected for a new DFC overlay for heavily travelled highways, their performance indicated that when properly constructed, these recycled mixes can perform to the same level as an equivalent mix containing no RAP.

Agency Survey

In 2008 the Ministry conducted a survey of other transportation agencies to identify current trends in recycling policies. The survey focused on the amount of RAP permitted, special requirements for working with RAP, and the determination of correct asphalt grade when using higher amounts of RAP.

Survey results showed the amount of RAP permitted ranged from none to unlimited, with more RAP permitted in binder courses (20 to 40 percent) than in surface courses. The average amount of RAP permitted was higher for the light traffic category than for the heavy or medium categories, though the pattern was less pronounced than it was for surface courses.

The success of the Highway 401 demonstration project, and the results of the survey of American Association of State Highway and Transportation Officials (AASHTO) member agencies show higher levels of RAP than specified in 2007 MTO standards can be successfully incorporated into a wide variety of surface courses.

Update of OPS Recycling Policy

As a result of both the Ministry’s successful experience and MTO’s survey results, MTO has changed its specifications for RAP usage. The Ministry now permits greater quantities of RAP in an innovative pavement recycling program. RAP is allowed in all mixes except for Stone Mastic Asphalt (SMA) surface courses, with up to 40 percent RAP now permitted in most binder courses, and up to 20 percent in all non-SMA surface courses. Depending on the course, mix type, and traffic level, up to 20 percent more RAP is now permitted. To ensure durability and friction requirements are maintained for surface mixes the RAP material must meet quality requirements matching those required for the new aggregates to be included in the surface mix. Changes have been made to Ontario Provincial Standards through special provision. The new levels of RAP permitted in provincial roadways are presented in the table below.

Conclusion

The Ministry is confident that the paving industry can produce HMA with higher percentages of RAP and has taken steps to permit HMA mix designers to make that choice. This also includes allowing RAP in mixes where we have traditionally not permitted any RAP, such as premium surface courses. This program provides sustainable road rehabilitation options that are designed to meet the needs of present-day users, and to ensure that the well being of future generations will not be compromised.

Besides permitting higher levels of RAP, MTO will continue its commitment to the use of a variety of environmentally sound pavement rehabilitation techniques, and will encourage contractors to take a holistic approach to green design. In the future, MTO would like to explore the possibility of including RAP in SMA surface courses on all classes of road. MTO is also exploring the use of Warm Mix Asphalt (WMA) technology as a sustainable pavement technology.

For more information see the Optimizing Use of Reclaimed Asphalt Pavement in Flexible Pavements in Ontario paper, published in the Canadian Technical Asphalt Association (CTAA) Proceedings for 2009 or please contact one of the following:

Pamela Marks, P.Eng., Senior Bituminous Engineer, Bituminous Section, Highway Standards Branch at 416-235-3724 or at Pamela.Marks@ontario.ca

Chris Raymond, PhD, P.Eng, Head, Bituminous Section, Highway Standards Branch at 416-235-3725 or at Chris.Raymond@ontario.ca