ISCP has chosen Minneapolis, Minnesota as its venue for the upcoming 12th International Conference on Concrete Pavements 2020—12th ICCP2020! According to the International Grooving & Grinding Association (IGGA), and Kristin Dispenza, IGGA Spokeswoman, in Minneapolis, Minnesota, USA, the inevitable freeze-thaw cycles lead to pavement damage every winter, prompting drivers to vocalize their desire for the city to fix potholes and maintain roads. Dispenza provided information about the problem and the strategy to Equipment World Online News. Every spring in Minneapolis, drivers find themselves trying to avoid the worst of the potholes and the damage that they sometimes do to vehicles. The expansion joints of concrete streets have deteriorated, moisture from rain or melted snow has gotten into these joints. Cracks combined with water, winter cold, and summer sun can lead to potholes. Dispenza explains that road owners have long looked to break this annual cycle by identifying repair methods that can better withstand the Midwest’s harsh winter weather. According to Dispenza, the City of Minneapolis’ “2017 Concrete Street Rehabilitation Program” is expected to implement cost-effective solutions. The work continues under the program though 2018. Minneapolis’s renewed pavements are expected to last another 25 years, making the total lifespan of the concrete streets 65-70 years. With only one major preservation cycle during that timeframe, this translates into a very low annual cost for concrete city streets.
There are 155 miles of residential concrete streets throughout the City of Minneapolis that were constructed between 1961 and 1976, making them an average of 45 years old. “It is common knowledge that there is a lot of life left in those pavements and that taking advantage of the remaining service life could save money in the long run,” said Matthew Zeller, Executive Director-Concrete Paving Association of Minnesota (CPAM).
When applied to a structurally sound pavement in the proper time frame, concrete pavement preservation (CPP) is an extremely beneficial approach—a series of engineered techniques developed over the past 50 years to rehabilitate and renew concrete pavement. These techniques have proven effective for deteriorated highways, but they also offer an alternative to asphalt overlays when rehabilitating city streets constructed of concrete. The process targets and repairs areas of distress within otherwise sound concrete pavements. CPP can be performed in small work areas and at off-peak hours, with the repairs often lasting for decades.
CPP is designed for well-worn pavement in need of renewal and is a sustainable approach because it reuses existing materials rather than requiring large quantities of natural resources such as aggregate and bituminous oil. In addition to extending pavement life, CCP improves a pavement’s surface friction, enhancing safety when utilizing diamond grinding and/or grooving. CPP’s basic techniques include:
- Slab stabilization: Restores support to concrete slabs by filling small voids that develop beneath the slab at joints, cracks or pavement edges.
- Full-depth repair (FDR): Fixes cracked slabs and joint deterioration by removing a portion of the existing slab full depth and replacing it with new concrete.
- Partial-depth repair: Corrects surface distresses and joint-crack deterioration in the upper third of the concrete slab that involves removing the deteriorated concrete, cleaning the patch area, placing new concrete and reforming the joint system, if necessary.
- Dowel bar retrofit: Involves cutting slots in the pavement across a transverse joint or crack, cleaning the slots, placing the dowel bars, and then backfilling the slots with new concrete. Dowel bar retrofits link slabs together at transverse cracks and joints, so that the load is evenly distributed across the crack or joint.
- Cross-stitching longitudinal cracks or joints: Repairs low-severity cracks. Reinforcing steel is added to hold the crack together tightly to preserve aggregate interlock.
- Conventional diamond grinding (CDG): Removes faulting, slab warping, studded-tire wear, and unevenness resulting from patches to create a smooth, uniform pavement profile. CDG reduces road noise by providing a longitudinal texture that is quieter than transverse textures. The longitudinal texture also enhances macro texture and skid resistance in worn and polished pavement surfaces.
- Joint and crack resealing: Minimizes the infiltration of surface water and incompressible material into the joint system. Less water entering the joint reduces subgrade softening, slows pumping and erosion of subbase fines, and may limit dowel bar corrosion caused by de-icing chemicals.
Sam Gramling, President and CEO-Interstate Improvement, Inc. explained, “Minneapolis’s residential streets have likely already exceeded their intended design life, but they’ve held up very well over time—largely because of the low volume of traffic—that performing these repairs will add 20-30 years of useful life.”
According to the Minneapolis Department of Public Works, the Minneapolis City Council recently authorized additional annual money for capital improvements in the city’s transportation system. As part of that authorization, the Concrete Street Rehabilitation Program was identified as a priority to extend the useful life of concrete streets throughout the city—primarily residential neighborhoods. The program will rehabilitate approximately 3-4 miles of concrete streets per year.
Strategic Planning Conserves Resources in Minneapolis
Over the next two years, it is expected that 80-85 of Minneapolis’s city blocks will be repaired as part of the Concrete Street Rehabilitation Program. Work is being performed by both city personnel and Interstate Improvement, Inc., along with that company’s subcontractors. This balance of public and private work was arrived at through experimentation and analysis.
For an early concrete repair project encompassing a five-six block area, two Minnesota-based contractors performed a partial depth repair and performed diamond grinding. The remainder of work was performed by the City of Minneapolis using its own maintenance staff. Lessons learned on this early project were used to determine the most effective way to proceed with the remainder of the rehabilitation work. In some instances (typically small, two-to-three block areas without specialized CPP needs) city forces are well-equipped to do the work themselves. In other locations, contractors are used to perform skilled work such as full- or partial-depth repair.
Another efficiency that The City of Minneapolis brought to the process was to conduct a thorough preconstruction assessment with various representatives from prime contractors, conduct site visits, assess the pavements before bidding the project, followed by a pre-bid meeting to discuss the constructability, and answer any questions. Concrete work is a specialized type of construction, therefore it makes sense for all project stakeholders to come together before site work actually begins.
Another means of enhancing the effectiveness of the Concrete Street Rehabilitation Program was to use Indefinite Delivery/Indefinite Quantity (IDIQ) contracting. IDIQ contracts outline overall project completion goals (usually quantified in number of years) and a minimum/maximum dollar amount for the overall contract. During construction, individual task orders are executed with a minimum dollar amount, which prevents situations in which the contractor would have to mobilize overly small work areas. The contracting method allows owners flexibility in performing work while dealing with ever-changing budget restraints. To manage their budget, owners can issue smaller or fewer task orders for a given project and then transfer leftover funds to a different project within the IDIQ pool of work. Conversely, if they get lower pricing than anticipated on an IDIQ project, more of the total projected work can be performed. IDIQ contracts usually span approximately two years, during which time contractors hold their pricing steady.
For the City of Minneapolis, the current project’s final completion date is December 31, 2018.
Concrete Pavement Restoration in Waite Park—Waite Park is a neighborhood in Northeast Minneapolis. The original pavements were constructed in 1967 and 1968 and were good candidates for concrete repair techniques. Concrete street repairs there were addressed with the 2017 concrete preservation strategy program are located in two distinct zones within the Waite Park neighborhood, totaling 6-8 miles of streets. Beginning in the summer of 2017, repairs consisted of saw cutting, full-depth concrete patching, partial depth concrete patching, diamond grinding, joint and crack sealing, spot curb replacement, manhole and inlet adjustments, ADA ramp construction and restoration. Diamond grinding was performed to create a smooth and safe finished surface. Traffic was managed using the city’s extensive alley system.
“With increasing demands and diminishing transportation funding, city managers are compelled to look for new and innovative ways to stretch their budgets and maximize pavement longevity,” says John Roberts, Executive Director-IGGA. “It is truly good fortune that their predecessors chose to build many of the city’s streets using long lasting concrete pavement. It is even more fortunate for the taxpayers of Minneapolis that their elected officials were willing to look at best practices abroad and develop a system of pavement renewal that is economical, long lasting and safe. I suspect that you will soon see other municipalities adopt this truly efficient model of pavement renewal, once word gets out.”
For the article in Better World Online Magazine, dollar amounts, contractors, and information on IGGA, please go to: https://www.equipmentworld.com/to-counter-damage-from-freeze-thaw-cycles-minneapolis-is-using-a-progressive-concrete-pavement-preservation-strategy/
An additional article on Minnesota Road Innovations in Roads and Bridges online magazine titled “Minnesota plans first smart road project” describes a Minnesota innovative technology:
A major corridor in Minneapolis will be the initial location to deploy connected-vehicle technology.
WSP USA was selected by the Minnesota Department of Transportation (MnDOT) to design Minnesota’s first smart road, which would transform a major state highway west of Minneapolis into a road capable of testing and deploying numerous connected-vehicle applications. The backbone of the Minnesota project will be the broadcast of signal, phase and timing (SPaT) information to vehicles directly from traffic signal controllers along the corridor. MnDOT will be developing the communications infrastructure and data management systems to support a range of existing and future technologies. To read the entire article, please go to: https://www.roadsbridges.com/minnesota-plans-first-smart-road-project
Home Page Photo: Full-depth joint removal under the
“Concrete Street Rehabilitation Program” in Minneapolis.
Dowel bars link slabs together at transverse cracks and
joints to help fix cracked slabs and joint deterioration. by IGGA