To Maintain Or Not To Maintain (That Is The Question)

Defining preventative maintenance for concrete pavement and the issues being prevented.

While concrete is a durable, long-lived pavement solution, some conditions— such as expansion and contraction due to temperature change, or deviations in mix ingredients—represent real-world challenges for any pavement, regardless of its material composition. Pavements are carefully engineered to accommodate the forces at work during their service life. But it is still important to regularly inspect roads, assess the extent of any pavement distress, and implement a fully adequate response.

Preventative maintenance is so named for a reason. Single problems can have a “domino effect” and, if left unaddressed, can eventually be responsible for multiple problems. Therefore, it is important to understand first the goals and best practices for the initial design and construction of concrete pavement, and second, how maintenance schedules and activities should be conducted to maximize the pavement’s life.

DESIGN & CONSTRUCTION CONSIDERATIONS

Concrete pavement distresses at times can manifest as cracking, broken slabs, buckling, or roughness, and these distress categories should be considered during a pavement’s design and construction phases.

Contraction joints are one critical consideration because reduced slab thickness along the line of a joint is intended to permit controlled cracking when the concrete shrinks. (For this reason, this type of joint is often called

Transverse cracks often require dowel bar retrofit to prevent faulting. Here, a crew from Ramsey County, Minnesota, drills holes for dowel bars for a full-depth repair job with a 36-in. Minnich A-1 single gang drill.

Concrete Paving Association of Minnesota Matthew J. Zeller

a “control” joint.) But joints can become filled with debris, or “incompressibles,” creating an overly rigid system that allows expansive stresses to build up. The compressive forces resulting from these stresses can cause cracking to occur in other areas of the pavement. Temperature ranges of more than 100 degrees F during a given year can translate to expansion- and contractionrelated changes of approximately 2/3 in. in a 100-ft .stretch of pavement.

Modern transverse contraction joints are typically spaced no more than 15-ft. apart based on the thickness of the section. If each joint successfully cracks throughout the depth of the slab below it, the pavement will function as designed and can accommodate weather-related expansion. However, if some of the joints fail to crack—for example, if the pavement cracks only at every second, third or more joints—this makes the effective length of each panel much greater than 15 ft. Consequently, when panels contract, they are opening the joint wider than was intended, allowing more incompressibles into the space. When expansion next occurs, there is less volume for the concrete to expand into due to the imcompressibles filling the voids. After several years of this cycle, as improper transmission of forces occurs, the pavement can buckle or break in its weakest points.

In Minnesota, for example, one strategy that has been used at the time of construction to prevent future problems associated with joint function include driving heavy loads (such as full water trucks or dump trucks) along the pavement shortly after joints have been sawn. This helps activate the joints, ensuring that a majority of them successfully crack, in turn keeping each crack tighter and more resistant to infill. Using joint sealant can also help keep incompressible materials out. It should also be noted that lengthening spacing between joints at the time of construction, which is sometimes done as a cost-saving measure, is not recommended.

To answer “to maintain or not to maintain:” yes. Well-designed and -constructed concrete pavement can last many decades. But to ensure that it reaches its full-service life—and has optimal rideability during each year of its life—agencies should develop a preventative maintenance plan. Small, regular interventions save time, money, and effort in the long run.

Matthew J. Zeller, P.E., is the Executive Director of the Concrete Paving Association of Minnesota. Provided by the International Grooving and Grinding Association.

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