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Pavement Preservation FAQs

The purpose of a pavement preservation program is to be “proactive” and not “reactive”. An effective Pavement Preservation Program is essential in protecting the state’s initial investment by keeping good roads in good condition. Research has shown that for every $1 spent on pavement preservation, the state can save at least $6 in road rehabilitation and reconstruction.  Currently the Department spends approximately 10% - 15% of the yearly resurfacing budget on various preservation treatments.

Q.  What is the normal method used to resurface a roadway?
Hot mix asphalt (often referred to as HMA) is a mixture of various sizes of aggregate which is bound together with asphaltic cement.  HMA is placed with a paving machine which contains electronic and manual controls that can put it at the proper grades and depths. Currently, the cost to apply a typical HMA can run anywhere from $60,000 to $90,000 a lane mile (1 lane, 1 mile long).  The price variation is due to several factors such as the location of the project to a hot mix asphalt plant (haul cost to a project is one of the most costly components of an asphalt mix), is the roadway section in the middle of city or urban area (which directly affects traffic control costs and also whether the project is a daytime or nighttime project (more costly), does the project require milling of the existing surface (removal of the old wearing surface) and etc.

Q.  Why does TDOT use pavement preservation methods?
Pavement preservation methods extend the life of a roadway at a third of the cost. A thorough analysis of any roadway’s condition (pavement age, traffic volume, surface deficiencies and etc.) indicates when application of a preservation treatment would be the most cost effective means of protecting the initial investment. We have learned that when a roadway begins to exhibit potholes and rutting, this is usually a sign of problems with base and/or sub-base failures. The work on these types of deficiencies is much more extensive and very expensive. Pavement preservation treatments are designed to prevent these types of big money problems.

Q.  What are the types of pavement preservation?

Microsurfacing
Microsurfacing is comprised of the following components – aggregate, asphalt emulsion, Portland cement and admixtures (which control the speed of the curing process).  Roads selected for microsurfacing are generally 8-15 years of age (time since last treatment) and are generally in good condition.  Microsurfacing is selected for any given section of roadway to help insure that a good roadway stays in good condition.  Also, microsurfacing provides a surface with great skid resistant qualities.  The typical lane mile cost of microsurfacing is about a third of the cost of HMA.
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Chip Seal
Chip seals are comprised of aggregate and asphalt emulsion.  Roads selected to receive a chip seal treatment can vary, but in most cases this treatment is selected due to the presence of moderate to heavy cracking throughout the pavement surface.  Chip seals are good at crack mitigation (slowing or retarding the reflection/growing of the existing cracks).  Chip seals can be used as a wearing surface for roadways with low ADT’s (average daily traffic – usually below 750).  Often, chip seals are utilized as an intermediate layer below the new wearing surface to slow or retard reflective cracking through the new surface.  The typical lane mile cost of a chip seal is generally 20% of the cost of HMA.
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Cape Seal
Cape seal treatments are a combination of two treatments – Chip seal and Microsurfacing.  The chip seal is placed first to help mitigate or seal the existing cracks in the existing wearing surface.  Next, a microsurfacing treatment is placed upon the chip seal to provide a smoother wearing surface along with good skid resistance capabilities.  The typical lane mile cost of a cape seal is generally half what it costs to do HMA overlay.

Longitudinal Joint Stabilization (LJS)
The Longitudinal joint stabilization (LJS) product is a pavement preservation material (rejuvenator) utilized to maintain the integrity of the longitudinal construction joint. Generally TDOT applies this treatment within 2-4 years after a resurfacing with HMA is complete. The purpose of the rejuvenator is to add back the lighter oils which are often burnt out of the hot asphalt mix during the production phase.  These lighter oils are what make an HMA a “flexible” pavement. 
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Crack Sealing
Crack sealing is a treatment that is very cost effective.  Much like the name suggests, the cracks are cleaned and sealed.  Typically, roadways that begin to exhibit cracking (not caused by base or subgrade failures) are selected for crack sealing.  This work often begins on roadways that are less than 6 years old since the last HMA overlay and could continue through most of the life of the pavement.  Water intrusion into the base or the binder mixes is one of the most detrimental forces encountered by the pavement structure.
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Thin Lift HMA Mixes
Thin Lift HMA Mixes are just what the name suggests, thinner applications of HMA.  These mixes utilize smaller aggregates, thus allowing thinner application rates.  Typically roadways selected for Thin Lift HMA’s are in relatively fair to good condition.  Much like a cape seal, Thin Lift HMA’s can be used in conjunction with an underlying chip seal application (for crack mitigation).  The typical lane mile cost for Thin Lift HMA’s (depending on treatment selected) is generally a third to half the cost of general HMA overlay.

www.pavementpreservation.org/ is a web site which helps explain the utilization of a pavement preservation program and the benefits that result from the successful implantation of such a program. Once you pull up the address, go to the reference library.  Then go to "A Quick Network Guide" for a brief but good explanation of what the Department is attempting to accomplish in its pavement preservation program.