A number of neighborhoods have recently been impacted due to roadway improvement projects called “Slurry Sealing”. The City is appreciative of everyone’s efforts to park down the street for a day or two and use different streets than normal to access their home. Many different comments and theories have popped into local social media about the use of slurry sealing. Our Public Works Department has put together some background on the topic that might help answer some of those questions, curiosities, and concerns.
When is slurry seal the preferred choice?
Slurry seals are part of the City’s pavement maintenance program that also includes asphalt overlays and complete rehabilitations. Staff performs inspections of the roadways throughout the City and uses the Pavement Condition Index (PCI) ranking system to rate the condition of the roadways. This PCI ranking is used to select roadways for the slurry seal project with the intent to extend the useful life of the roadway and provide a re-invigorated driving surface.
Slurry seal is a cost-effective maintenance strategy that is used on residential roadways throughout the community to extend roadway life. Prior to the actual application of the slurry seal, Street Department staff perform minor maintenance work on the roadways that include patching and crack sealing. Once this maintenance work is completed a contractor then applies the slurry seal product that seals the roadway and prevents water from infiltrating the subsurface and damaging the pavement system.
Public Works completes one large scale slurry seal project each biennium and has employed this pavement maintenance strategy for decades as part of the total pavement maintenance program. The current slurry seal project was awarded by the City Council at the June 16, 2020 Business Meeting, Staff Report.
What actually is slurry seal?
A slurry seal is the application of a mixture of water, asphalt emulsion, aggregate (very small crushed rock), and additives to an existing asphalt pavement surface. A slurry seal is similar to a fog seal except the slurry seal has aggregates as part of the mixture. This combined mixture of the emulsion and aggregates represents “slurry.” Polymer is commonly added to the asphalt emulsion to provide better mixture properties. The placement of this mixture on existing pavement is the “seal” as it is intended to seal the pavement surface. Slurry seals are generally used on residential streets.
How does it work?
Slurry seal is applied in order to help preserve and protect the underlying pavement structure and provide a new driving surface. Roads chosen for slurry seal applications generally have low to moderate distress and narrow crack width. Slurry seal applications serve to seal the cracks, restore lost flexibility to the pavement surface, provide a deep, rich black pavement surface color, and help preserve the underlying pavement structure.
What roads get slurry seal applied and how often?
Slurry seal is typically applied on either an intermittent or cyclical basis. Location, weather, traffic loading, and pavement conditions are factors used to determine if a slurry seal application is appropriate. Roadways selected for slurry seal treatment are commonly those which have slight to moderate distress, no rutting, and generally narrow crack widths, and where a slurry seal treatment would help extend the pavement life until resurfacing becomes necessary.
Roadways chosen for cyclical slurry seal applications would typically be treated every five to seven years.