Crack Sealing Is the Lowest-Cost, Highest-Benefit Pavement Preservation Treatment
The inevitability of decay should be a great motivator for planned, preventive maintenance, especially when considering the alternatives. Yet, surprisingly, many view routine maintenance tasks as time-consuming, expensive, and insignificant. This can be true of all industries, but especially with pavement and roadways.
Proper road maintenance can take a variety of forms, but all share the goal of keeping roads as close to their original condition as possible. The Federal Highway Administration defines preventive pavement maintenance as “a planned strategy of cost-effective treatments to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, and maintains or improves the functional condition of the roadway system.”
Road systems are among the most significant public assets and make vital economic contributions to society. Responding to pavement ills only when major issues occur is not the definition of preventive maintenance but, rather, incurs the cost of neglect. Like all good care, effective preventive maintenance requires an adoption of routine measures to ensure road systems remain in optimum working condition.
COST OF NEGLECT
Of the estimated 33,000 traffic fatalities that occur each year, one-third involve poor road conditions. In 2017, the American Society of Civil Engineers (ASEC) released the most recent edition of its quadrennial Infrastructure Report Card of the country’s byways. The nation received an overall D+.
No one denies distresses in road systems are the inevitable result of the continued oxidization and deterioration of asphalt and man-made forces such as heavy traffic. Failing to stay on top of preventive maintenance creates hazardous conditions that can precipitate indirect expenses and cause entire road systems to fall into disrepair.
Between 2009 and 2011, according to a 2014 report by Smart Growth America, about 45 percent of transportation spending across all states went to repairs, while 55 percent funded new roads. Also, in the last decade, the percentage of roads categorized as in “poor condition” grew from 14 to 20 percent, while the number of roads in “good condition” barely moved.
“When considering existing roads comprise 99 percent of all roads in the country (new roads are just one percent), state DOTs may need to reprioritize their spending toward maintenance, even if there are no ribbon cutting ceremonies for repair jobs,” says Roger Miller of Smart Growth America.
In the absence of treatment, the crack evolves to cupping and lipping. Before long what was once a very treatable crack has developed into a full-blown pothole.
Crack sealing is the most common pavement preservation option with the highest-benefit-to-cost ratio. Studies show a dollar spent on early preventive maintenance, such as crack sealing, can delay or eliminate $6 to $14 in future rehabilitation costs.
When cracks are left untreated, approximately 75 percent will form into potholes within just three years. If crack sealing is done early and often, only 1 percent of cracks will form into potholes within the same length of time.
According to a recent group study conducted by the National Center for Asphalt Technology, “crack sealing and filling are cost-effective treatments that provide life-extending benefits when applied to pavements in good, fair and poor conditions.”
These treatments consist of applying a highly elastic material into pavement cracks to prevent or reduce the intrusion of water and incompressible materials. The benefits of crack sealing include decreasing further crack deterioration, protecting the pavement structure from moisture damage and ultimately extending the pavement life.
To ascertain how much life-extending benefit could be gained from crack sealing and other preservation treatments, the NCAT study, in partnership with MnROAD, applied the construction of full-scale test sections along a two-lane country road and access route to a quarry and asphalt plant.
While the study reaffirmed crack sealing’s documented ability to extend service life in pavement categorized as in “good condition,” the data found crack sealing and filling’s life-extending benefits apply not only to pavements categorized as in “good condition,” but pavements with “fair” and “poor” conditions as well.
Crack sealing distressed pavement is proven to reduce potholes, extend sealant and pavement service life and, when performed prior to other surface treatments, improve the overall effectiveness of any stand-alone treatment.
ADDED VALUE IN ROUTING
From hot to cold and cold to hot, pavement materials expand and contract when subjected to temperature changes. Understanding the laws of thermodynamics can improve the preparation that’s paramount to crack sealant success. And depending on a pavement’s condition, a sealant application’s service life can be greatly enhanced by routing.
Routing prepares the crack before sealing. Routing along a crack path creates a reservoir free of debris and provides the necessary width and depth to support the right amount of sealant for longer-lasting protection. The advantages of routing are widely known and supported by long- and short-term studies to extend service life up to 7 years, improve sealant adherence by 40 percent and double service life.
However, a perception that the routing process constricts overall productivity has led many industry professionals to skip this step. With the purpose of examining crack treatments, the Strategic Highway Research Program H-106 Crack Treatment Study conducted the most extensive pavement maintenance experiment ever.
After a thorough examination, routing was found not to be a rate-determining step and does not slow down productivity of an experienced crew when crack sealing. With real insight into the process of routing, industry professionals should now be inspired to rout when necessary in order to extend the service life of pavement and the sealant applied.
The million-dollar question moving forward is: Will awareness of pavement preventive maintenance and the ongoing research recognizing the low cost of preservation treatments — particularly crack sealing as the lowest-cost, highest-benefit preservation treatment — be enough to convince agency leaders and property owners to adopt routine maintenance plans?
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