Transportation Infrastructure

Best practices for long-life pavement from design and construction to preservation and maintenance.

The overlaying of concrete on asphalt, composite or old concrete pavements provides an environmentally friendly, long-lasting and cost-effective rehabilitation pavement solution.

As with any built infrastructure, good construction is key to ensuring a concrete pavement structure performs to expectations. Construction activities for concrete pavements can range from simple, hand-placement fixed form practices, to highly sophisticated operations with fully automated equipment. Uniformity of the subgrade and base structures are the most critical aspect of concrete pavement construction, as it ensures the concrete distributes the traffic load uniformly and no dynamic loading is present due to varied supporting strengths throughout the length of pavement project. An equally important consideration is ensuring proper drainage is in-place within and surrounding the base structure. Without proper drainage, the concrete pavement can experience severe effects such as: erosion of the base structure, non-uniform support causing dynamic loading of the concrete and potential slab cracking, increased warping stresses due to high moisture differential from the top and bottom of the slab, and potential decreased freeze-thaw performance causing premature joint failure.

Concrete pavement thickness design methods have and continue to evolve across North America, as new innovations in cement manufacturing, concrete mix design, and the incorporation of additives and fibres are constantly under development, providing improved performance and durability in thinner pavement sections.

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Interlocking concrete pavement (ICP) pavers are a versatile, multi-purpose pavement alternative that are becoming a popular solution across many areas in Canada. They can be utilized in both architectural and structurally functional applications, including streetscaping, delineation of crosswalks, or heavy-duty applications like ports or airports. Increasingly, ICP are being used as an infiltration solution to restore the natural ability of an urban site to absorb stormwater. They can play an important role in flood mitigation in urban environments.

Concrete is hard, rigid and durable—it is the traditional material of choice for constructing buildings, bridges and other types of infrastructure. For the same reasons, concrete is also an excellent choice for roads. Concrete roads can deliver superior value and performance over their lifetime. According to independent research, concrete roads can save money, reduce harmful emissions, improve safety, and spare users the aggravation of roads under constant repair. Subgrades and subbases are also an important part of any pavement structure.  It is important to have a good understanding of the insitu subgrade material characteristics to determine if they meet specification requirements or if they need to be removed or modified. The key for concrete pavements is uniformity of the subgrade strength to prevent dynamic loading on the concrete pavement.

Life-cycle cost analysis (LCCA) is a tool to determine the most cost-effective option among different competing alternatives to purchase, own, operate, maintain and, finally, dispose of an object or process, when each is equally appropriate to be implemented on technical grounds. For a pavement, in addition to the initial construction cost, LCCA takes into account all agency costs related to future activities, including future maintenance and rehabilitation. On occasion, user costs are also considered (e.g., reduced capacity at work zones). All the costs are usually discounted and total to a present-day value known as net present value (NPV).

In addition to its long-term durability and reduced maintenance, concrete offers several other sustainable benefits over its lifecycle.

Pervious concrete is a porous medium that allows storm water to drain from the surface to the underlying base and soil structures. It is comprised of a gap graded aggregate with little to no sand, creating a concrete with a void structure that maximizes stormwater infiltration and provides a low impact development alternative to overland drainage designs. Increasingly, porous pavements are being recognized by local regulations as a best management practice for stormwater control. When properly maintained, pervious concrete pavements present a long-lasting alternative for applications like parking lots, alley ways, and low volume roads.

Precast concrete pavements are a relatively new type of pavement system slowly gaining popularity in North America because of its prefabricated, modular nature, which allows for expedited construction schedules over asphalt and cast-in-place concrete. Precast pavement slabs are particularly useful for rehabilitation of highly traveled concrete roadways because of the difficulty in re-routing traffic. The precast pavement repair technique may also be useful for highways of much lower ADT at certain locations such as approaches to bridges where shoulders for accommodating traffic detours are minimal or non-existent (i.e. main thoroughfares, ramps, intersections, bridge approaches, roundabouts, as well as airfield runways and taxiways). Additionally, precast concrete pavements provide innovative maintenance solutions, and panels can be standardized to address common roadwork like utility cuts, or re-used for temporary repair activities.

Determining the timing of preservation or rehabilitation activities over the service life of a pavement is critical to ensuring a pavement meets or exceeds its expected performance according to its design. With transportation agencies facing rising traffic volumes and reduced budgets, it is therefore also critical to ensure the scheduling of routine and major maintenance activities throughout the life of the pavement to maintain an acceptable serviceability index at the lowest cost to the stakeholders. Rehabilitation activities for concrete pavements include: resealing of joints, replacing/restoring malfunctioning joints (i.e. dowel bar retro-fits or cross-stitching), grinding of pavements to restore smoothness, partial or full-depth repairs, removing deteriorated materials, strengthening of bases or subbases, filling of voids under the concrete with slab jacking techniques, concrete overlay installations over existing concrete or asphalt structures, and adding drains.

Just as building designs are increasingly focused on resilient performance against the threats of climate change, so too is core public infrastructure adapting with increased risks of flooding, temperature extremes and freeze-thaw swings. The National Research Council of Canada, alongside universities and other research bodies, have been undertaking research related to the effects of climate events on public infrastructure and transportation networks, including an examination of future-looking climate data and flooding, and is working to improve design guidelines to address the effects on bridges and roads.

Roller Compacted Concrete (RCC) is a durable, economical and sustainable pavement solution, which gets its name from the heavy vibratory and rubber-tired rollers used to compact its final form. RCC is a heavy-duty pavement, used when large paved areas must stand up to heavy vehicle loads, abrasive environments and sharp turning movements, as well as, hydraulic and oil spills and specialized equipment. Below is a table entitled Roller-Compacted Concrete (RCC) Performance identifying the features and benefits of RCC. Typical applications for RCC include industrial pavements and heavy-duty parking lots, in addition to several specialized uses in ports, intermodal yards, snow melt sites, scrap metal facilities, and dams.

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