Wednesday, March 31, 2010

Seeing Cracks in last summer's street Slurry Seal?

Seeing Cracks in last summer's street Slurry Seal? here's why:‏

The city recently heard from a resident of the Englewood neighborhood (near Hazelwood Loop) asking about cracks in the street within a year of the city’s application of a Slurry Seal to the street. Listed below is information from one of the city’s engineers about why that occurs. -Joanne

The cracks showing through new slurry seal is a normal occurrence and will be evident on all streets. This is because the asphalt pavement is flexible (compared to other paving materials), while slurry seal is more rigid. As heavier vehicles (such as garbage trucks) roll over the pavement, it flexes and the old cracks, even though they are sealed, transfer through the slurry seal and become visible again. This is not a problem because the underlying crack is sealed with flexible material that seals the pavement and extends the pavement life.

Eventually, along with the existing cracks, new cracks will appear that were too small to be seen when the cracks were sealed last year. This is a normal part of the pavement life. The advantage of the slurry seal is that the new cracks will take longer to develop, but they will still appear. These new cracks will be sealed as part of our routine crack seal program.

The main purpose of the slurry seal is to restore the pavement surface. As pavement ages, the cumulative effects of weather and vehicle usage causes deterioration of the asphalt binder (the sticky stuff that holds the road together) from the top down, resulting in widespread cracking if not treated. In a slurry seal, what looks like black paint is actually a blend of asphalt binder mixed with sand that restores the top layer of this sticky binder to seal and preserve the pavement and keep it lasting longer. It’s true that a street doesn’t look as good after a Slurry seal as it would after a thicker pavement overlay. However, as slurry seals cost much less than pavement overlays, we have found slurry seals to be a much better way to preserve and protect the pavement of our local streets, extending pavement life.

We inspected the contractors work as they apply the slurry seal to see that the slurry seal product was properly applied. We also inspect streets over the years to monitor pavement condition. This way we can monitor the results over time and evaluate that the project costs spent achieved the desired result. We will be monitoring the pavement condition in your neighborhood as part of the regular review. We are confident that the combination of deeper crack sealing (the work done before the seal was applied) and the slurry seal will extend the pavement’s useful life, but not forever.

Please feel free to contact me with any further questions.

Thank you,

Mike McCarthy

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