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NV5 Employees Rick Rome and Tammy Kelley Write Article for CAC Publication



Cemeterian, June 2011: Pages 2-3

If you’re a roadway in Colorado (and you could talk), the answer to that question is probably a definite “Yes”! Cracks and potholes are unfortunately very prevalent in Colorado and climates where the winters can bring a number of freeze thaw cycles. And just like fixing a water pipe that has frozen and burst, fixing roadways in the wake of a long winter can be very expensive. In a perfect world we would rip the road out and design the perfect roadway drainage system with all of the right materials…well, we don’t live in that perfect world, nor do most have the money for that roadway!

How did this happen? As we all know, understanding a problem is the first step to fixing the problem. What causes these potholes and the cracking in the road? Whether made of concrete or asphalt, roadways often develop cracks over time that allows water to seep in and infiltrate the materials that make up the base of the roadway. In the fall and winter months this water spells big trouble for pavements. Ice floats because it is less dense than water. This means that water can get into smaller space than ice, freeze and make bigger spaces. Anyone who has ever filled a glass or a bottle with water and placed it in the freezer knows that if you forget it, the container may explode. Just like a predictable plot line in a bad movie, you can guess what happens when water seeps into the cracks and crevices of a road. No surprises here, it freezes and expands. Water may pool under the pavement, forcing the roadway upwards. It may pool in a crack, forcing the pavement apart. Over time, the force of the expanding water breaks down the structural and adhesive materials constituting the pavement. Vehicles roll over the weakened pavement, putting pressure on it. The road begins to disintegrate. Pieces of the road move away from each other and a pothole forms. Over time, repeated freeze-thaw action weakens the road. In February and March, the repeated freezing and thawing of the road exacerbates potholes. Ice under and inside the cracks in the road melts from the top down, letting in more water that freezes, thaws, and moves the pavement further apart. It is a cycle that continues until the temperatures stay above freezing.

An Ounce of Prevention is worth a Pound of Cure. If you are ahead of the game, you can try to prevent cracking that leads to potholes with good roadway design. Above all else, start with a geotechnical engineer that knows what they are doing! The engineer will recommend appropriate base materials that retain very little water — reducing the amount of ice that forms under the road. They will also recommend the appropriate grade, or slope, to the crown of the road that will allow water to drain off and away from the road. A good consultant will also look at what type of equipment will operate on the road and design for that weight. A comprehensive design and subgrade preparation limits the potential for water to seep into asphalt and make cracks.

Maintenance of a road system is essential to keeping a lasting and crack free road. Road maintenance includes things like plowing snow to prevent ice from forming, application of a seal coat to prevent water from seeping onto the asphalt surface, and street sweeping depending on how much and the kind of debris that gets on the road. These types of activities will extend the useful life of the roads. If it’s too late for prevention, then repair can be a cost effective approach before cracks become potholes. There are a variety of products on the market for patching and sealing these areas is often called “crack sealing”. Generally, this method can be applied to cracks that are ¼ to 1″ in thickness. Pay close attention to the outside temperature though, asphalt is sensitive to too much cold which can impact the quality of the repair. However, in this short article there is no way to detail all of the types of cracks and how a professional determines the best method and materials for repair.

Repairing Potholes
If you didn’t stop reading before now, chances are that there are potholes that need fixing. Once again, it is very important to consult an engineer or very knowledgeable contractor before starting repairs. They will help you to develop the best plan of attack, as well as the best materials to use for each particular situation. A fix in one cemetery may not work in another! The goal with the fix is once again aimed at sealing the surface of the roadway.

As with crack sealing, this is not the time to skimp on professional advice or materials. If you use high quality patching materials and processes that do not allow water to enter again, it will pay off in lower maintenance expenses in the future. The process of placing the appropriate materials into holes and larger cracks, packing it, and repeating this process until the holes are back in line with the grade creates a sturdy road patch. If the material settles and a sagged surface appears it will be a pothole again next year. Potholes are the bane of winter and spring drivers, but with some knowledge of geological processes and diligent pavement creation and management, they can be prevented and repaired. If you’re looking for more about these topics, the internet is a gateway to a wealth of information. Many Departments of Transportation websites provide further information of the geology of freeze thaw cycles, types of cracks and how each of them are created, as well as general repair methods.

If you are interested in further reading, following are some sites of interest:

Colorado State Publications Library, “Short-term crack sealant performance and reducing bumps and transverse cracking in new hot mix asphalt overlays over crack sealants,” by Shuler, Scott.

California Department of Transportation (CALTRANS). Caltrans Flexible Pavement Materials Program – Chapter 3 Crack Sealing & Crack Filling.

TranSafety, Inc. Crack Sealing Benefits and Techniques.

Suite101: What Makes Potholes Form?: Freeze Thaw Processes, Weathering, and the Geology of Pavement.

CAC thanks Rick Rome, Tammy Kelley and Nolte Vertical Five for their contribution to this issue.